3261 строка
82 KiB
C
3261 строка
82 KiB
C
/*
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* fs/dcache.c
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*
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* Complete reimplementation
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* (C) 1997 Thomas Schoebel-Theuer,
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* with heavy changes by Linus Torvalds
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*/
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/*
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* Notes on the allocation strategy:
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*
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* The dcache is a master of the icache - whenever a dcache entry
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* exists, the inode will always exist. "iput()" is done either when
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* the dcache entry is deleted or garbage collected.
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*/
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#include <linux/syscalls.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/fs.h>
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#include <linux/fsnotify.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/cache.h>
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#include <linux/export.h>
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#include <linux/mount.h>
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#include <linux/file.h>
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#include <asm/uaccess.h>
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#include <linux/security.h>
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#include <linux/seqlock.h>
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#include <linux/swap.h>
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#include <linux/bootmem.h>
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#include <linux/fs_struct.h>
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#include <linux/hardirq.h>
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#include <linux/bit_spinlock.h>
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#include <linux/rculist_bl.h>
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#include <linux/prefetch.h>
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#include <linux/ratelimit.h>
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#include "internal.h"
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#include "mount.h"
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/*
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* Usage:
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* dcache->d_inode->i_lock protects:
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* - i_dentry, d_alias, d_inode of aliases
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* dcache_hash_bucket lock protects:
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* - the dcache hash table
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* s_anon bl list spinlock protects:
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* - the s_anon list (see __d_drop)
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* dcache_lru_lock protects:
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* - the dcache lru lists and counters
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* d_lock protects:
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* - d_flags
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* - d_name
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* - d_lru
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* - d_count
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* - d_unhashed()
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* - d_parent and d_subdirs
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* - childrens' d_child and d_parent
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* - d_alias, d_inode
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*
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* Ordering:
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* dentry->d_inode->i_lock
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* dentry->d_lock
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* dcache_lru_lock
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* dcache_hash_bucket lock
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* s_anon lock
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*
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* If there is an ancestor relationship:
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* dentry->d_parent->...->d_parent->d_lock
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* ...
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* dentry->d_parent->d_lock
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* dentry->d_lock
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*
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* If no ancestor relationship:
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* if (dentry1 < dentry2)
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* dentry1->d_lock
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* dentry2->d_lock
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*/
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int sysctl_vfs_cache_pressure __read_mostly = 100;
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EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
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EXPORT_SYMBOL(rename_lock);
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static struct kmem_cache *dentry_cache __read_mostly;
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/**
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* read_seqbegin_or_lock - begin a sequence number check or locking block
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* lock: sequence lock
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* seq : sequence number to be checked
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*
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* First try it once optimistically without taking the lock. If that fails,
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* take the lock. The sequence number is also used as a marker for deciding
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* whether to be a reader (even) or writer (odd).
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* N.B. seq must be initialized to an even number to begin with.
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*/
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static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq)
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{
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if (!(*seq & 1)) /* Even */
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*seq = read_seqbegin(lock);
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else /* Odd */
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write_seqlock(lock);
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}
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static inline int need_seqretry(seqlock_t *lock, int seq)
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{
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return !(seq & 1) && read_seqretry(lock, seq);
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}
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static inline void done_seqretry(seqlock_t *lock, int seq)
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{
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if (seq & 1)
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write_sequnlock(lock);
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}
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/*
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* This is the single most critical data structure when it comes
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* to the dcache: the hashtable for lookups. Somebody should try
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* to make this good - I've just made it work.
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*
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* This hash-function tries to avoid losing too many bits of hash
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* information, yet avoid using a prime hash-size or similar.
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*/
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#define D_HASHBITS d_hash_shift
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#define D_HASHMASK d_hash_mask
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static unsigned int d_hash_mask __read_mostly;
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static unsigned int d_hash_shift __read_mostly;
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static struct hlist_bl_head *dentry_hashtable __read_mostly;
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static inline struct hlist_bl_head *d_hash(const struct dentry *parent,
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unsigned int hash)
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{
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hash += (unsigned long) parent / L1_CACHE_BYTES;
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hash = hash + (hash >> D_HASHBITS);
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return dentry_hashtable + (hash & D_HASHMASK);
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}
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/* Statistics gathering. */
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struct dentry_stat_t dentry_stat = {
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.age_limit = 45,
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};
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static DEFINE_PER_CPU(unsigned int, nr_dentry);
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
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static int get_nr_dentry(void)
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{
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int i;
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int sum = 0;
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for_each_possible_cpu(i)
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sum += per_cpu(nr_dentry, i);
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return sum < 0 ? 0 : sum;
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}
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int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
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size_t *lenp, loff_t *ppos)
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{
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dentry_stat.nr_dentry = get_nr_dentry();
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return proc_dointvec(table, write, buffer, lenp, ppos);
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}
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#endif
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/*
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* Compare 2 name strings, return 0 if they match, otherwise non-zero.
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* The strings are both count bytes long, and count is non-zero.
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*/
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#ifdef CONFIG_DCACHE_WORD_ACCESS
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#include <asm/word-at-a-time.h>
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/*
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* NOTE! 'cs' and 'scount' come from a dentry, so it has a
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* aligned allocation for this particular component. We don't
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* strictly need the load_unaligned_zeropad() safety, but it
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* doesn't hurt either.
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*
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* In contrast, 'ct' and 'tcount' can be from a pathname, and do
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* need the careful unaligned handling.
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*/
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static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
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{
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unsigned long a,b,mask;
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for (;;) {
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a = *(unsigned long *)cs;
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b = load_unaligned_zeropad(ct);
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if (tcount < sizeof(unsigned long))
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break;
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if (unlikely(a != b))
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return 1;
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cs += sizeof(unsigned long);
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ct += sizeof(unsigned long);
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tcount -= sizeof(unsigned long);
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if (!tcount)
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return 0;
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}
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mask = ~(~0ul << tcount*8);
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return unlikely(!!((a ^ b) & mask));
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}
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#else
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static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
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{
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do {
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if (*cs != *ct)
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return 1;
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cs++;
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ct++;
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tcount--;
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} while (tcount);
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return 0;
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}
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#endif
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static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
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{
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const unsigned char *cs;
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/*
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* Be careful about RCU walk racing with rename:
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* use ACCESS_ONCE to fetch the name pointer.
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*
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* NOTE! Even if a rename will mean that the length
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* was not loaded atomically, we don't care. The
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* RCU walk will check the sequence count eventually,
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* and catch it. And we won't overrun the buffer,
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* because we're reading the name pointer atomically,
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* and a dentry name is guaranteed to be properly
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* terminated with a NUL byte.
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*
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* End result: even if 'len' is wrong, we'll exit
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* early because the data cannot match (there can
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* be no NUL in the ct/tcount data)
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*/
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cs = ACCESS_ONCE(dentry->d_name.name);
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smp_read_barrier_depends();
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return dentry_string_cmp(cs, ct, tcount);
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}
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static void __d_free(struct rcu_head *head)
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{
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struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
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WARN_ON(!hlist_unhashed(&dentry->d_alias));
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if (dname_external(dentry))
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kfree(dentry->d_name.name);
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kmem_cache_free(dentry_cache, dentry);
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}
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/*
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* no locks, please.
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*/
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static void d_free(struct dentry *dentry)
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{
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BUG_ON((int)dentry->d_lockref.count > 0);
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this_cpu_dec(nr_dentry);
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if (dentry->d_op && dentry->d_op->d_release)
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dentry->d_op->d_release(dentry);
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/* if dentry was never visible to RCU, immediate free is OK */
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if (!(dentry->d_flags & DCACHE_RCUACCESS))
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__d_free(&dentry->d_u.d_rcu);
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else
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call_rcu(&dentry->d_u.d_rcu, __d_free);
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}
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/**
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* dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
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* @dentry: the target dentry
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* After this call, in-progress rcu-walk path lookup will fail. This
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* should be called after unhashing, and after changing d_inode (if
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* the dentry has not already been unhashed).
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*/
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static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
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{
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assert_spin_locked(&dentry->d_lock);
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/* Go through a barrier */
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write_seqcount_barrier(&dentry->d_seq);
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}
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/*
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* Release the dentry's inode, using the filesystem
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* d_iput() operation if defined. Dentry has no refcount
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* and is unhashed.
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*/
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static void dentry_iput(struct dentry * dentry)
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__releases(dentry->d_lock)
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__releases(dentry->d_inode->i_lock)
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{
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struct inode *inode = dentry->d_inode;
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if (inode) {
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dentry->d_inode = NULL;
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hlist_del_init(&dentry->d_alias);
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spin_unlock(&dentry->d_lock);
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spin_unlock(&inode->i_lock);
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if (!inode->i_nlink)
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fsnotify_inoderemove(inode);
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if (dentry->d_op && dentry->d_op->d_iput)
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dentry->d_op->d_iput(dentry, inode);
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else
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iput(inode);
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} else {
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spin_unlock(&dentry->d_lock);
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}
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}
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/*
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* Release the dentry's inode, using the filesystem
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* d_iput() operation if defined. dentry remains in-use.
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*/
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static void dentry_unlink_inode(struct dentry * dentry)
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__releases(dentry->d_lock)
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__releases(dentry->d_inode->i_lock)
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{
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struct inode *inode = dentry->d_inode;
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dentry->d_inode = NULL;
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hlist_del_init(&dentry->d_alias);
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dentry_rcuwalk_barrier(dentry);
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spin_unlock(&dentry->d_lock);
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spin_unlock(&inode->i_lock);
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if (!inode->i_nlink)
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fsnotify_inoderemove(inode);
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if (dentry->d_op && dentry->d_op->d_iput)
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dentry->d_op->d_iput(dentry, inode);
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else
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iput(inode);
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}
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/*
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* dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
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*/
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static void dentry_lru_add(struct dentry *dentry)
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{
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if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) {
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spin_lock(&dcache_lru_lock);
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dentry->d_flags |= DCACHE_LRU_LIST;
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list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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dentry->d_sb->s_nr_dentry_unused++;
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dentry_stat.nr_unused++;
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spin_unlock(&dcache_lru_lock);
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}
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}
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static void __dentry_lru_del(struct dentry *dentry)
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{
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list_del_init(&dentry->d_lru);
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dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
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dentry->d_sb->s_nr_dentry_unused--;
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dentry_stat.nr_unused--;
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}
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/*
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* Remove a dentry with references from the LRU.
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*/
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static void dentry_lru_del(struct dentry *dentry)
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{
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if (!list_empty(&dentry->d_lru)) {
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spin_lock(&dcache_lru_lock);
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__dentry_lru_del(dentry);
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spin_unlock(&dcache_lru_lock);
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}
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}
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static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
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{
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spin_lock(&dcache_lru_lock);
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if (list_empty(&dentry->d_lru)) {
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dentry->d_flags |= DCACHE_LRU_LIST;
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list_add_tail(&dentry->d_lru, list);
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dentry->d_sb->s_nr_dentry_unused++;
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dentry_stat.nr_unused++;
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} else {
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list_move_tail(&dentry->d_lru, list);
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}
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spin_unlock(&dcache_lru_lock);
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}
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/**
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* d_kill - kill dentry and return parent
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* @dentry: dentry to kill
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* @parent: parent dentry
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*
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* The dentry must already be unhashed and removed from the LRU.
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*
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* If this is the root of the dentry tree, return NULL.
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*
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* dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
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* d_kill.
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*/
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static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
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__releases(dentry->d_lock)
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__releases(parent->d_lock)
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__releases(dentry->d_inode->i_lock)
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{
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list_del(&dentry->d_u.d_child);
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/*
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* Inform try_to_ascend() that we are no longer attached to the
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* dentry tree
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*/
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dentry->d_flags |= DCACHE_DENTRY_KILLED;
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if (parent)
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spin_unlock(&parent->d_lock);
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dentry_iput(dentry);
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/*
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* dentry_iput drops the locks, at which point nobody (except
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* transient RCU lookups) can reach this dentry.
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*/
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d_free(dentry);
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return parent;
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}
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/*
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* Unhash a dentry without inserting an RCU walk barrier or checking that
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* dentry->d_lock is locked. The caller must take care of that, if
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* appropriate.
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*/
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static void __d_shrink(struct dentry *dentry)
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{
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if (!d_unhashed(dentry)) {
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struct hlist_bl_head *b;
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if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
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b = &dentry->d_sb->s_anon;
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else
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b = d_hash(dentry->d_parent, dentry->d_name.hash);
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hlist_bl_lock(b);
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__hlist_bl_del(&dentry->d_hash);
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dentry->d_hash.pprev = NULL;
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hlist_bl_unlock(b);
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}
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}
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/**
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* d_drop - drop a dentry
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* @dentry: dentry to drop
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*
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* d_drop() unhashes the entry from the parent dentry hashes, so that it won't
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* be found through a VFS lookup any more. Note that this is different from
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* deleting the dentry - d_delete will try to mark the dentry negative if
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* possible, giving a successful _negative_ lookup, while d_drop will
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* just make the cache lookup fail.
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*
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* d_drop() is used mainly for stuff that wants to invalidate a dentry for some
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* reason (NFS timeouts or autofs deletes).
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*
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* __d_drop requires dentry->d_lock.
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*/
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void __d_drop(struct dentry *dentry)
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{
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if (!d_unhashed(dentry)) {
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__d_shrink(dentry);
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dentry_rcuwalk_barrier(dentry);
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}
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}
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EXPORT_SYMBOL(__d_drop);
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void d_drop(struct dentry *dentry)
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{
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spin_lock(&dentry->d_lock);
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__d_drop(dentry);
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spin_unlock(&dentry->d_lock);
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}
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EXPORT_SYMBOL(d_drop);
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/*
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* Finish off a dentry we've decided to kill.
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* dentry->d_lock must be held, returns with it unlocked.
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* If ref is non-zero, then decrement the refcount too.
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* Returns dentry requiring refcount drop, or NULL if we're done.
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*/
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static inline struct dentry *dentry_kill(struct dentry *dentry)
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__releases(dentry->d_lock)
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{
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struct inode *inode;
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struct dentry *parent;
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inode = dentry->d_inode;
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if (inode && !spin_trylock(&inode->i_lock)) {
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relock:
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spin_unlock(&dentry->d_lock);
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cpu_relax();
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return dentry; /* try again with same dentry */
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}
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if (IS_ROOT(dentry))
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parent = NULL;
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else
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parent = dentry->d_parent;
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if (parent && !spin_trylock(&parent->d_lock)) {
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if (inode)
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spin_unlock(&inode->i_lock);
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goto relock;
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}
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/*
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* The dentry is now unrecoverably dead to the world.
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*/
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lockref_mark_dead(&dentry->d_lockref);
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/*
|
|
* inform the fs via d_prune that this dentry is about to be
|
|
* unhashed and destroyed.
|
|
*/
|
|
if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
|
|
dentry->d_op->d_prune(dentry);
|
|
|
|
dentry_lru_del(dentry);
|
|
/* if it was on the hash then remove it */
|
|
__d_drop(dentry);
|
|
return d_kill(dentry, parent);
|
|
}
|
|
|
|
/*
|
|
* This is dput
|
|
*
|
|
* This is complicated by the fact that we do not want to put
|
|
* dentries that are no longer on any hash chain on the unused
|
|
* list: we'd much rather just get rid of them immediately.
|
|
*
|
|
* However, that implies that we have to traverse the dentry
|
|
* tree upwards to the parents which might _also_ now be
|
|
* scheduled for deletion (it may have been only waiting for
|
|
* its last child to go away).
|
|
*
|
|
* This tail recursion is done by hand as we don't want to depend
|
|
* on the compiler to always get this right (gcc generally doesn't).
|
|
* Real recursion would eat up our stack space.
|
|
*/
|
|
|
|
/*
|
|
* dput - release a dentry
|
|
* @dentry: dentry to release
|
|
*
|
|
* Release a dentry. This will drop the usage count and if appropriate
|
|
* call the dentry unlink method as well as removing it from the queues and
|
|
* releasing its resources. If the parent dentries were scheduled for release
|
|
* they too may now get deleted.
|
|
*/
|
|
void dput(struct dentry *dentry)
|
|
{
|
|
if (unlikely(!dentry))
|
|
return;
|
|
|
|
repeat:
|
|
if (lockref_put_or_lock(&dentry->d_lockref))
|
|
return;
|
|
|
|
/* Unreachable? Get rid of it */
|
|
if (unlikely(d_unhashed(dentry)))
|
|
goto kill_it;
|
|
|
|
if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
|
|
if (dentry->d_op->d_delete(dentry))
|
|
goto kill_it;
|
|
}
|
|
|
|
dentry->d_flags |= DCACHE_REFERENCED;
|
|
dentry_lru_add(dentry);
|
|
|
|
dentry->d_lockref.count--;
|
|
spin_unlock(&dentry->d_lock);
|
|
return;
|
|
|
|
kill_it:
|
|
dentry = dentry_kill(dentry);
|
|
if (dentry)
|
|
goto repeat;
|
|
}
|
|
EXPORT_SYMBOL(dput);
|
|
|
|
/**
|
|
* d_invalidate - invalidate a dentry
|
|
* @dentry: dentry to invalidate
|
|
*
|
|
* Try to invalidate the dentry if it turns out to be
|
|
* possible. If there are other dentries that can be
|
|
* reached through this one we can't delete it and we
|
|
* return -EBUSY. On success we return 0.
|
|
*
|
|
* no dcache lock.
|
|
*/
|
|
|
|
int d_invalidate(struct dentry * dentry)
|
|
{
|
|
/*
|
|
* If it's already been dropped, return OK.
|
|
*/
|
|
spin_lock(&dentry->d_lock);
|
|
if (d_unhashed(dentry)) {
|
|
spin_unlock(&dentry->d_lock);
|
|
return 0;
|
|
}
|
|
/*
|
|
* Check whether to do a partial shrink_dcache
|
|
* to get rid of unused child entries.
|
|
*/
|
|
if (!list_empty(&dentry->d_subdirs)) {
|
|
spin_unlock(&dentry->d_lock);
|
|
shrink_dcache_parent(dentry);
|
|
spin_lock(&dentry->d_lock);
|
|
}
|
|
|
|
/*
|
|
* Somebody else still using it?
|
|
*
|
|
* If it's a directory, we can't drop it
|
|
* for fear of somebody re-populating it
|
|
* with children (even though dropping it
|
|
* would make it unreachable from the root,
|
|
* we might still populate it if it was a
|
|
* working directory or similar).
|
|
* We also need to leave mountpoints alone,
|
|
* directory or not.
|
|
*/
|
|
if (dentry->d_lockref.count > 1 && dentry->d_inode) {
|
|
if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
|
|
spin_unlock(&dentry->d_lock);
|
|
return -EBUSY;
|
|
}
|
|
}
|
|
|
|
__d_drop(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(d_invalidate);
|
|
|
|
/* This must be called with d_lock held */
|
|
static inline void __dget_dlock(struct dentry *dentry)
|
|
{
|
|
dentry->d_lockref.count++;
|
|
}
|
|
|
|
static inline void __dget(struct dentry *dentry)
|
|
{
|
|
lockref_get(&dentry->d_lockref);
|
|
}
|
|
|
|
struct dentry *dget_parent(struct dentry *dentry)
|
|
{
|
|
int gotref;
|
|
struct dentry *ret;
|
|
|
|
/*
|
|
* Do optimistic parent lookup without any
|
|
* locking.
|
|
*/
|
|
rcu_read_lock();
|
|
ret = ACCESS_ONCE(dentry->d_parent);
|
|
gotref = lockref_get_not_zero(&ret->d_lockref);
|
|
rcu_read_unlock();
|
|
if (likely(gotref)) {
|
|
if (likely(ret == ACCESS_ONCE(dentry->d_parent)))
|
|
return ret;
|
|
dput(ret);
|
|
}
|
|
|
|
repeat:
|
|
/*
|
|
* Don't need rcu_dereference because we re-check it was correct under
|
|
* the lock.
|
|
*/
|
|
rcu_read_lock();
|
|
ret = dentry->d_parent;
|
|
spin_lock(&ret->d_lock);
|
|
if (unlikely(ret != dentry->d_parent)) {
|
|
spin_unlock(&ret->d_lock);
|
|
rcu_read_unlock();
|
|
goto repeat;
|
|
}
|
|
rcu_read_unlock();
|
|
BUG_ON(!ret->d_lockref.count);
|
|
ret->d_lockref.count++;
|
|
spin_unlock(&ret->d_lock);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(dget_parent);
|
|
|
|
/**
|
|
* d_find_alias - grab a hashed alias of inode
|
|
* @inode: inode in question
|
|
* @want_discon: flag, used by d_splice_alias, to request
|
|
* that only a DISCONNECTED alias be returned.
|
|
*
|
|
* If inode has a hashed alias, or is a directory and has any alias,
|
|
* acquire the reference to alias and return it. Otherwise return NULL.
|
|
* Notice that if inode is a directory there can be only one alias and
|
|
* it can be unhashed only if it has no children, or if it is the root
|
|
* of a filesystem.
|
|
*
|
|
* If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
|
|
* any other hashed alias over that one unless @want_discon is set,
|
|
* in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
|
|
*/
|
|
static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
|
|
{
|
|
struct dentry *alias, *discon_alias;
|
|
|
|
again:
|
|
discon_alias = NULL;
|
|
hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
|
|
spin_lock(&alias->d_lock);
|
|
if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
|
|
if (IS_ROOT(alias) &&
|
|
(alias->d_flags & DCACHE_DISCONNECTED)) {
|
|
discon_alias = alias;
|
|
} else if (!want_discon) {
|
|
__dget_dlock(alias);
|
|
spin_unlock(&alias->d_lock);
|
|
return alias;
|
|
}
|
|
}
|
|
spin_unlock(&alias->d_lock);
|
|
}
|
|
if (discon_alias) {
|
|
alias = discon_alias;
|
|
spin_lock(&alias->d_lock);
|
|
if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
|
|
if (IS_ROOT(alias) &&
|
|
(alias->d_flags & DCACHE_DISCONNECTED)) {
|
|
__dget_dlock(alias);
|
|
spin_unlock(&alias->d_lock);
|
|
return alias;
|
|
}
|
|
}
|
|
spin_unlock(&alias->d_lock);
|
|
goto again;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
struct dentry *d_find_alias(struct inode *inode)
|
|
{
|
|
struct dentry *de = NULL;
|
|
|
|
if (!hlist_empty(&inode->i_dentry)) {
|
|
spin_lock(&inode->i_lock);
|
|
de = __d_find_alias(inode, 0);
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
return de;
|
|
}
|
|
EXPORT_SYMBOL(d_find_alias);
|
|
|
|
/*
|
|
* Try to kill dentries associated with this inode.
|
|
* WARNING: you must own a reference to inode.
|
|
*/
|
|
void d_prune_aliases(struct inode *inode)
|
|
{
|
|
struct dentry *dentry;
|
|
restart:
|
|
spin_lock(&inode->i_lock);
|
|
hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
|
|
spin_lock(&dentry->d_lock);
|
|
if (!dentry->d_lockref.count) {
|
|
/*
|
|
* inform the fs via d_prune that this dentry
|
|
* is about to be unhashed and destroyed.
|
|
*/
|
|
if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
|
|
!d_unhashed(dentry))
|
|
dentry->d_op->d_prune(dentry);
|
|
|
|
__dget_dlock(dentry);
|
|
__d_drop(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
spin_unlock(&inode->i_lock);
|
|
dput(dentry);
|
|
goto restart;
|
|
}
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
EXPORT_SYMBOL(d_prune_aliases);
|
|
|
|
/*
|
|
* Try to throw away a dentry - free the inode, dput the parent.
|
|
* Requires dentry->d_lock is held, and dentry->d_count == 0.
|
|
* Releases dentry->d_lock.
|
|
*
|
|
* This may fail if locks cannot be acquired no problem, just try again.
|
|
*/
|
|
static void try_prune_one_dentry(struct dentry *dentry)
|
|
__releases(dentry->d_lock)
|
|
{
|
|
struct dentry *parent;
|
|
|
|
parent = dentry_kill(dentry);
|
|
/*
|
|
* If dentry_kill returns NULL, we have nothing more to do.
|
|
* if it returns the same dentry, trylocks failed. In either
|
|
* case, just loop again.
|
|
*
|
|
* Otherwise, we need to prune ancestors too. This is necessary
|
|
* to prevent quadratic behavior of shrink_dcache_parent(), but
|
|
* is also expected to be beneficial in reducing dentry cache
|
|
* fragmentation.
|
|
*/
|
|
if (!parent)
|
|
return;
|
|
if (parent == dentry)
|
|
return;
|
|
|
|
/* Prune ancestors. */
|
|
dentry = parent;
|
|
while (dentry) {
|
|
if (lockref_put_or_lock(&dentry->d_lockref))
|
|
return;
|
|
dentry = dentry_kill(dentry);
|
|
}
|
|
}
|
|
|
|
static void shrink_dentry_list(struct list_head *list)
|
|
{
|
|
struct dentry *dentry;
|
|
|
|
rcu_read_lock();
|
|
for (;;) {
|
|
dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
|
|
if (&dentry->d_lru == list)
|
|
break; /* empty */
|
|
spin_lock(&dentry->d_lock);
|
|
if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
|
|
spin_unlock(&dentry->d_lock);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* We found an inuse dentry which was not removed from
|
|
* the LRU because of laziness during lookup. Do not free
|
|
* it - just keep it off the LRU list.
|
|
*/
|
|
if (dentry->d_lockref.count) {
|
|
dentry_lru_del(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
continue;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
|
|
try_prune_one_dentry(dentry);
|
|
|
|
rcu_read_lock();
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/**
|
|
* prune_dcache_sb - shrink the dcache
|
|
* @sb: superblock
|
|
* @count: number of entries to try to free
|
|
*
|
|
* Attempt to shrink the superblock dcache LRU by @count entries. This is
|
|
* done when we need more memory an called from the superblock shrinker
|
|
* function.
|
|
*
|
|
* This function may fail to free any resources if all the dentries are in
|
|
* use.
|
|
*/
|
|
void prune_dcache_sb(struct super_block *sb, int count)
|
|
{
|
|
struct dentry *dentry;
|
|
LIST_HEAD(referenced);
|
|
LIST_HEAD(tmp);
|
|
|
|
relock:
|
|
spin_lock(&dcache_lru_lock);
|
|
while (!list_empty(&sb->s_dentry_lru)) {
|
|
dentry = list_entry(sb->s_dentry_lru.prev,
|
|
struct dentry, d_lru);
|
|
BUG_ON(dentry->d_sb != sb);
|
|
|
|
if (!spin_trylock(&dentry->d_lock)) {
|
|
spin_unlock(&dcache_lru_lock);
|
|
cpu_relax();
|
|
goto relock;
|
|
}
|
|
|
|
if (dentry->d_flags & DCACHE_REFERENCED) {
|
|
dentry->d_flags &= ~DCACHE_REFERENCED;
|
|
list_move(&dentry->d_lru, &referenced);
|
|
spin_unlock(&dentry->d_lock);
|
|
} else {
|
|
list_move_tail(&dentry->d_lru, &tmp);
|
|
dentry->d_flags |= DCACHE_SHRINK_LIST;
|
|
spin_unlock(&dentry->d_lock);
|
|
if (!--count)
|
|
break;
|
|
}
|
|
cond_resched_lock(&dcache_lru_lock);
|
|
}
|
|
if (!list_empty(&referenced))
|
|
list_splice(&referenced, &sb->s_dentry_lru);
|
|
spin_unlock(&dcache_lru_lock);
|
|
|
|
shrink_dentry_list(&tmp);
|
|
}
|
|
|
|
/**
|
|
* shrink_dcache_sb - shrink dcache for a superblock
|
|
* @sb: superblock
|
|
*
|
|
* Shrink the dcache for the specified super block. This is used to free
|
|
* the dcache before unmounting a file system.
|
|
*/
|
|
void shrink_dcache_sb(struct super_block *sb)
|
|
{
|
|
LIST_HEAD(tmp);
|
|
|
|
spin_lock(&dcache_lru_lock);
|
|
while (!list_empty(&sb->s_dentry_lru)) {
|
|
list_splice_init(&sb->s_dentry_lru, &tmp);
|
|
spin_unlock(&dcache_lru_lock);
|
|
shrink_dentry_list(&tmp);
|
|
spin_lock(&dcache_lru_lock);
|
|
}
|
|
spin_unlock(&dcache_lru_lock);
|
|
}
|
|
EXPORT_SYMBOL(shrink_dcache_sb);
|
|
|
|
/*
|
|
* destroy a single subtree of dentries for unmount
|
|
* - see the comments on shrink_dcache_for_umount() for a description of the
|
|
* locking
|
|
*/
|
|
static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
|
|
{
|
|
struct dentry *parent;
|
|
|
|
BUG_ON(!IS_ROOT(dentry));
|
|
|
|
for (;;) {
|
|
/* descend to the first leaf in the current subtree */
|
|
while (!list_empty(&dentry->d_subdirs))
|
|
dentry = list_entry(dentry->d_subdirs.next,
|
|
struct dentry, d_u.d_child);
|
|
|
|
/* consume the dentries from this leaf up through its parents
|
|
* until we find one with children or run out altogether */
|
|
do {
|
|
struct inode *inode;
|
|
|
|
/*
|
|
* inform the fs that this dentry is about to be
|
|
* unhashed and destroyed.
|
|
*/
|
|
if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
|
|
!d_unhashed(dentry))
|
|
dentry->d_op->d_prune(dentry);
|
|
|
|
dentry_lru_del(dentry);
|
|
__d_shrink(dentry);
|
|
|
|
if (dentry->d_lockref.count != 0) {
|
|
printk(KERN_ERR
|
|
"BUG: Dentry %p{i=%lx,n=%s}"
|
|
" still in use (%d)"
|
|
" [unmount of %s %s]\n",
|
|
dentry,
|
|
dentry->d_inode ?
|
|
dentry->d_inode->i_ino : 0UL,
|
|
dentry->d_name.name,
|
|
dentry->d_lockref.count,
|
|
dentry->d_sb->s_type->name,
|
|
dentry->d_sb->s_id);
|
|
BUG();
|
|
}
|
|
|
|
if (IS_ROOT(dentry)) {
|
|
parent = NULL;
|
|
list_del(&dentry->d_u.d_child);
|
|
} else {
|
|
parent = dentry->d_parent;
|
|
parent->d_lockref.count--;
|
|
list_del(&dentry->d_u.d_child);
|
|
}
|
|
|
|
inode = dentry->d_inode;
|
|
if (inode) {
|
|
dentry->d_inode = NULL;
|
|
hlist_del_init(&dentry->d_alias);
|
|
if (dentry->d_op && dentry->d_op->d_iput)
|
|
dentry->d_op->d_iput(dentry, inode);
|
|
else
|
|
iput(inode);
|
|
}
|
|
|
|
d_free(dentry);
|
|
|
|
/* finished when we fall off the top of the tree,
|
|
* otherwise we ascend to the parent and move to the
|
|
* next sibling if there is one */
|
|
if (!parent)
|
|
return;
|
|
dentry = parent;
|
|
} while (list_empty(&dentry->d_subdirs));
|
|
|
|
dentry = list_entry(dentry->d_subdirs.next,
|
|
struct dentry, d_u.d_child);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* destroy the dentries attached to a superblock on unmounting
|
|
* - we don't need to use dentry->d_lock because:
|
|
* - the superblock is detached from all mountings and open files, so the
|
|
* dentry trees will not be rearranged by the VFS
|
|
* - s_umount is write-locked, so the memory pressure shrinker will ignore
|
|
* any dentries belonging to this superblock that it comes across
|
|
* - the filesystem itself is no longer permitted to rearrange the dentries
|
|
* in this superblock
|
|
*/
|
|
void shrink_dcache_for_umount(struct super_block *sb)
|
|
{
|
|
struct dentry *dentry;
|
|
|
|
if (down_read_trylock(&sb->s_umount))
|
|
BUG();
|
|
|
|
dentry = sb->s_root;
|
|
sb->s_root = NULL;
|
|
dentry->d_lockref.count--;
|
|
shrink_dcache_for_umount_subtree(dentry);
|
|
|
|
while (!hlist_bl_empty(&sb->s_anon)) {
|
|
dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
|
|
shrink_dcache_for_umount_subtree(dentry);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This tries to ascend one level of parenthood, but
|
|
* we can race with renaming, so we need to re-check
|
|
* the parenthood after dropping the lock and check
|
|
* that the sequence number still matches.
|
|
*/
|
|
static struct dentry *try_to_ascend(struct dentry *old, unsigned seq)
|
|
{
|
|
struct dentry *new = old->d_parent;
|
|
|
|
rcu_read_lock();
|
|
spin_unlock(&old->d_lock);
|
|
spin_lock(&new->d_lock);
|
|
|
|
/*
|
|
* might go back up the wrong parent if we have had a rename
|
|
* or deletion
|
|
*/
|
|
if (new != old->d_parent ||
|
|
(old->d_flags & DCACHE_DENTRY_KILLED) ||
|
|
need_seqretry(&rename_lock, seq)) {
|
|
spin_unlock(&new->d_lock);
|
|
new = NULL;
|
|
}
|
|
rcu_read_unlock();
|
|
return new;
|
|
}
|
|
|
|
/**
|
|
* enum d_walk_ret - action to talke during tree walk
|
|
* @D_WALK_CONTINUE: contrinue walk
|
|
* @D_WALK_QUIT: quit walk
|
|
* @D_WALK_NORETRY: quit when retry is needed
|
|
* @D_WALK_SKIP: skip this dentry and its children
|
|
*/
|
|
enum d_walk_ret {
|
|
D_WALK_CONTINUE,
|
|
D_WALK_QUIT,
|
|
D_WALK_NORETRY,
|
|
D_WALK_SKIP,
|
|
};
|
|
|
|
/**
|
|
* d_walk - walk the dentry tree
|
|
* @parent: start of walk
|
|
* @data: data passed to @enter() and @finish()
|
|
* @enter: callback when first entering the dentry
|
|
* @finish: callback when successfully finished the walk
|
|
*
|
|
* The @enter() and @finish() callbacks are called with d_lock held.
|
|
*/
|
|
static void d_walk(struct dentry *parent, void *data,
|
|
enum d_walk_ret (*enter)(void *, struct dentry *),
|
|
void (*finish)(void *))
|
|
{
|
|
struct dentry *this_parent;
|
|
struct list_head *next;
|
|
unsigned seq = 0;
|
|
enum d_walk_ret ret;
|
|
bool retry = true;
|
|
|
|
again:
|
|
read_seqbegin_or_lock(&rename_lock, &seq);
|
|
this_parent = parent;
|
|
spin_lock(&this_parent->d_lock);
|
|
|
|
ret = enter(data, this_parent);
|
|
switch (ret) {
|
|
case D_WALK_CONTINUE:
|
|
break;
|
|
case D_WALK_QUIT:
|
|
case D_WALK_SKIP:
|
|
goto out_unlock;
|
|
case D_WALK_NORETRY:
|
|
retry = false;
|
|
break;
|
|
}
|
|
repeat:
|
|
next = this_parent->d_subdirs.next;
|
|
resume:
|
|
while (next != &this_parent->d_subdirs) {
|
|
struct list_head *tmp = next;
|
|
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
|
|
next = tmp->next;
|
|
|
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
|
|
|
|
ret = enter(data, dentry);
|
|
switch (ret) {
|
|
case D_WALK_CONTINUE:
|
|
break;
|
|
case D_WALK_QUIT:
|
|
spin_unlock(&dentry->d_lock);
|
|
goto out_unlock;
|
|
case D_WALK_NORETRY:
|
|
retry = false;
|
|
break;
|
|
case D_WALK_SKIP:
|
|
spin_unlock(&dentry->d_lock);
|
|
continue;
|
|
}
|
|
|
|
if (!list_empty(&dentry->d_subdirs)) {
|
|
spin_unlock(&this_parent->d_lock);
|
|
spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
|
|
this_parent = dentry;
|
|
spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
|
|
goto repeat;
|
|
}
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
/*
|
|
* All done at this level ... ascend and resume the search.
|
|
*/
|
|
if (this_parent != parent) {
|
|
struct dentry *child = this_parent;
|
|
this_parent = try_to_ascend(this_parent, seq);
|
|
if (!this_parent)
|
|
goto rename_retry;
|
|
next = child->d_u.d_child.next;
|
|
goto resume;
|
|
}
|
|
if (need_seqretry(&rename_lock, seq)) {
|
|
spin_unlock(&this_parent->d_lock);
|
|
goto rename_retry;
|
|
}
|
|
if (finish)
|
|
finish(data);
|
|
|
|
out_unlock:
|
|
spin_unlock(&this_parent->d_lock);
|
|
done_seqretry(&rename_lock, seq);
|
|
return;
|
|
|
|
rename_retry:
|
|
if (!retry)
|
|
return;
|
|
seq = 1;
|
|
goto again;
|
|
}
|
|
|
|
/*
|
|
* Search for at least 1 mount point in the dentry's subdirs.
|
|
* We descend to the next level whenever the d_subdirs
|
|
* list is non-empty and continue searching.
|
|
*/
|
|
|
|
/**
|
|
* have_submounts - check for mounts over a dentry
|
|
* @parent: dentry to check.
|
|
*
|
|
* Return true if the parent or its subdirectories contain
|
|
* a mount point
|
|
*/
|
|
|
|
static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
|
|
{
|
|
int *ret = data;
|
|
if (d_mountpoint(dentry)) {
|
|
*ret = 1;
|
|
return D_WALK_QUIT;
|
|
}
|
|
return D_WALK_CONTINUE;
|
|
}
|
|
|
|
int have_submounts(struct dentry *parent)
|
|
{
|
|
int ret = 0;
|
|
|
|
d_walk(parent, &ret, check_mount, NULL);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(have_submounts);
|
|
|
|
/*
|
|
* Called by mount code to set a mountpoint and check if the mountpoint is
|
|
* reachable (e.g. NFS can unhash a directory dentry and then the complete
|
|
* subtree can become unreachable).
|
|
*
|
|
* Only one of check_submounts_and_drop() and d_set_mounted() must succeed. For
|
|
* this reason take rename_lock and d_lock on dentry and ancestors.
|
|
*/
|
|
int d_set_mounted(struct dentry *dentry)
|
|
{
|
|
struct dentry *p;
|
|
int ret = -ENOENT;
|
|
write_seqlock(&rename_lock);
|
|
for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
|
|
/* Need exclusion wrt. check_submounts_and_drop() */
|
|
spin_lock(&p->d_lock);
|
|
if (unlikely(d_unhashed(p))) {
|
|
spin_unlock(&p->d_lock);
|
|
goto out;
|
|
}
|
|
spin_unlock(&p->d_lock);
|
|
}
|
|
spin_lock(&dentry->d_lock);
|
|
if (!d_unlinked(dentry)) {
|
|
dentry->d_flags |= DCACHE_MOUNTED;
|
|
ret = 0;
|
|
}
|
|
spin_unlock(&dentry->d_lock);
|
|
out:
|
|
write_sequnlock(&rename_lock);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Search the dentry child list of the specified parent,
|
|
* and move any unused dentries to the end of the unused
|
|
* list for prune_dcache(). We descend to the next level
|
|
* whenever the d_subdirs list is non-empty and continue
|
|
* searching.
|
|
*
|
|
* It returns zero iff there are no unused children,
|
|
* otherwise it returns the number of children moved to
|
|
* the end of the unused list. This may not be the total
|
|
* number of unused children, because select_parent can
|
|
* drop the lock and return early due to latency
|
|
* constraints.
|
|
*/
|
|
|
|
struct select_data {
|
|
struct dentry *start;
|
|
struct list_head dispose;
|
|
int found;
|
|
};
|
|
|
|
static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
|
|
{
|
|
struct select_data *data = _data;
|
|
enum d_walk_ret ret = D_WALK_CONTINUE;
|
|
|
|
if (data->start == dentry)
|
|
goto out;
|
|
|
|
/*
|
|
* move only zero ref count dentries to the dispose list.
|
|
*
|
|
* Those which are presently on the shrink list, being processed
|
|
* by shrink_dentry_list(), shouldn't be moved. Otherwise the
|
|
* loop in shrink_dcache_parent() might not make any progress
|
|
* and loop forever.
|
|
*/
|
|
if (dentry->d_lockref.count) {
|
|
dentry_lru_del(dentry);
|
|
} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
|
|
dentry_lru_move_list(dentry, &data->dispose);
|
|
dentry->d_flags |= DCACHE_SHRINK_LIST;
|
|
data->found++;
|
|
ret = D_WALK_NORETRY;
|
|
}
|
|
/*
|
|
* We can return to the caller if we have found some (this
|
|
* ensures forward progress). We'll be coming back to find
|
|
* the rest.
|
|
*/
|
|
if (data->found && need_resched())
|
|
ret = D_WALK_QUIT;
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* shrink_dcache_parent - prune dcache
|
|
* @parent: parent of entries to prune
|
|
*
|
|
* Prune the dcache to remove unused children of the parent dentry.
|
|
*/
|
|
void shrink_dcache_parent(struct dentry *parent)
|
|
{
|
|
for (;;) {
|
|
struct select_data data;
|
|
|
|
INIT_LIST_HEAD(&data.dispose);
|
|
data.start = parent;
|
|
data.found = 0;
|
|
|
|
d_walk(parent, &data, select_collect, NULL);
|
|
if (!data.found)
|
|
break;
|
|
|
|
shrink_dentry_list(&data.dispose);
|
|
cond_resched();
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(shrink_dcache_parent);
|
|
|
|
static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry)
|
|
{
|
|
struct select_data *data = _data;
|
|
|
|
if (d_mountpoint(dentry)) {
|
|
data->found = -EBUSY;
|
|
return D_WALK_QUIT;
|
|
}
|
|
|
|
return select_collect(_data, dentry);
|
|
}
|
|
|
|
static void check_and_drop(void *_data)
|
|
{
|
|
struct select_data *data = _data;
|
|
|
|
if (d_mountpoint(data->start))
|
|
data->found = -EBUSY;
|
|
if (!data->found)
|
|
__d_drop(data->start);
|
|
}
|
|
|
|
/**
|
|
* check_submounts_and_drop - prune dcache, check for submounts and drop
|
|
*
|
|
* All done as a single atomic operation relative to has_unlinked_ancestor().
|
|
* Returns 0 if successfully unhashed @parent. If there were submounts then
|
|
* return -EBUSY.
|
|
*
|
|
* @dentry: dentry to prune and drop
|
|
*/
|
|
int check_submounts_and_drop(struct dentry *dentry)
|
|
{
|
|
int ret = 0;
|
|
|
|
/* Negative dentries can be dropped without further checks */
|
|
if (!dentry->d_inode) {
|
|
d_drop(dentry);
|
|
goto out;
|
|
}
|
|
|
|
for (;;) {
|
|
struct select_data data;
|
|
|
|
INIT_LIST_HEAD(&data.dispose);
|
|
data.start = dentry;
|
|
data.found = 0;
|
|
|
|
d_walk(dentry, &data, check_and_collect, check_and_drop);
|
|
ret = data.found;
|
|
|
|
if (!list_empty(&data.dispose))
|
|
shrink_dentry_list(&data.dispose);
|
|
|
|
if (ret <= 0)
|
|
break;
|
|
|
|
cond_resched();
|
|
}
|
|
|
|
out:
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(check_submounts_and_drop);
|
|
|
|
/**
|
|
* __d_alloc - allocate a dcache entry
|
|
* @sb: filesystem it will belong to
|
|
* @name: qstr of the name
|
|
*
|
|
* Allocates a dentry. It returns %NULL if there is insufficient memory
|
|
* available. On a success the dentry is returned. The name passed in is
|
|
* copied and the copy passed in may be reused after this call.
|
|
*/
|
|
|
|
struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
|
|
{
|
|
struct dentry *dentry;
|
|
char *dname;
|
|
|
|
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
|
|
if (!dentry)
|
|
return NULL;
|
|
|
|
/*
|
|
* We guarantee that the inline name is always NUL-terminated.
|
|
* This way the memcpy() done by the name switching in rename
|
|
* will still always have a NUL at the end, even if we might
|
|
* be overwriting an internal NUL character
|
|
*/
|
|
dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
|
|
if (name->len > DNAME_INLINE_LEN-1) {
|
|
dname = kmalloc(name->len + 1, GFP_KERNEL);
|
|
if (!dname) {
|
|
kmem_cache_free(dentry_cache, dentry);
|
|
return NULL;
|
|
}
|
|
} else {
|
|
dname = dentry->d_iname;
|
|
}
|
|
|
|
dentry->d_name.len = name->len;
|
|
dentry->d_name.hash = name->hash;
|
|
memcpy(dname, name->name, name->len);
|
|
dname[name->len] = 0;
|
|
|
|
/* Make sure we always see the terminating NUL character */
|
|
smp_wmb();
|
|
dentry->d_name.name = dname;
|
|
|
|
dentry->d_lockref.count = 1;
|
|
dentry->d_flags = 0;
|
|
spin_lock_init(&dentry->d_lock);
|
|
seqcount_init(&dentry->d_seq);
|
|
dentry->d_inode = NULL;
|
|
dentry->d_parent = dentry;
|
|
dentry->d_sb = sb;
|
|
dentry->d_op = NULL;
|
|
dentry->d_fsdata = NULL;
|
|
INIT_HLIST_BL_NODE(&dentry->d_hash);
|
|
INIT_LIST_HEAD(&dentry->d_lru);
|
|
INIT_LIST_HEAD(&dentry->d_subdirs);
|
|
INIT_HLIST_NODE(&dentry->d_alias);
|
|
INIT_LIST_HEAD(&dentry->d_u.d_child);
|
|
d_set_d_op(dentry, dentry->d_sb->s_d_op);
|
|
|
|
this_cpu_inc(nr_dentry);
|
|
|
|
return dentry;
|
|
}
|
|
|
|
/**
|
|
* d_alloc - allocate a dcache entry
|
|
* @parent: parent of entry to allocate
|
|
* @name: qstr of the name
|
|
*
|
|
* Allocates a dentry. It returns %NULL if there is insufficient memory
|
|
* available. On a success the dentry is returned. The name passed in is
|
|
* copied and the copy passed in may be reused after this call.
|
|
*/
|
|
struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
|
|
{
|
|
struct dentry *dentry = __d_alloc(parent->d_sb, name);
|
|
if (!dentry)
|
|
return NULL;
|
|
|
|
spin_lock(&parent->d_lock);
|
|
/*
|
|
* don't need child lock because it is not subject
|
|
* to concurrency here
|
|
*/
|
|
__dget_dlock(parent);
|
|
dentry->d_parent = parent;
|
|
list_add(&dentry->d_u.d_child, &parent->d_subdirs);
|
|
spin_unlock(&parent->d_lock);
|
|
|
|
return dentry;
|
|
}
|
|
EXPORT_SYMBOL(d_alloc);
|
|
|
|
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
|
|
{
|
|
struct dentry *dentry = __d_alloc(sb, name);
|
|
if (dentry)
|
|
dentry->d_flags |= DCACHE_DISCONNECTED;
|
|
return dentry;
|
|
}
|
|
EXPORT_SYMBOL(d_alloc_pseudo);
|
|
|
|
struct dentry *d_alloc_name(struct dentry *parent, const char *name)
|
|
{
|
|
struct qstr q;
|
|
|
|
q.name = name;
|
|
q.len = strlen(name);
|
|
q.hash = full_name_hash(q.name, q.len);
|
|
return d_alloc(parent, &q);
|
|
}
|
|
EXPORT_SYMBOL(d_alloc_name);
|
|
|
|
void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
|
|
{
|
|
WARN_ON_ONCE(dentry->d_op);
|
|
WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
|
|
DCACHE_OP_COMPARE |
|
|
DCACHE_OP_REVALIDATE |
|
|
DCACHE_OP_WEAK_REVALIDATE |
|
|
DCACHE_OP_DELETE ));
|
|
dentry->d_op = op;
|
|
if (!op)
|
|
return;
|
|
if (op->d_hash)
|
|
dentry->d_flags |= DCACHE_OP_HASH;
|
|
if (op->d_compare)
|
|
dentry->d_flags |= DCACHE_OP_COMPARE;
|
|
if (op->d_revalidate)
|
|
dentry->d_flags |= DCACHE_OP_REVALIDATE;
|
|
if (op->d_weak_revalidate)
|
|
dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
|
|
if (op->d_delete)
|
|
dentry->d_flags |= DCACHE_OP_DELETE;
|
|
if (op->d_prune)
|
|
dentry->d_flags |= DCACHE_OP_PRUNE;
|
|
|
|
}
|
|
EXPORT_SYMBOL(d_set_d_op);
|
|
|
|
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
|
|
{
|
|
spin_lock(&dentry->d_lock);
|
|
if (inode) {
|
|
if (unlikely(IS_AUTOMOUNT(inode)))
|
|
dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
|
|
hlist_add_head(&dentry->d_alias, &inode->i_dentry);
|
|
}
|
|
dentry->d_inode = inode;
|
|
dentry_rcuwalk_barrier(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
fsnotify_d_instantiate(dentry, inode);
|
|
}
|
|
|
|
/**
|
|
* d_instantiate - fill in inode information for a dentry
|
|
* @entry: dentry to complete
|
|
* @inode: inode to attach to this dentry
|
|
*
|
|
* Fill in inode information in the entry.
|
|
*
|
|
* This turns negative dentries into productive full members
|
|
* of society.
|
|
*
|
|
* NOTE! This assumes that the inode count has been incremented
|
|
* (or otherwise set) by the caller to indicate that it is now
|
|
* in use by the dcache.
|
|
*/
|
|
|
|
void d_instantiate(struct dentry *entry, struct inode * inode)
|
|
{
|
|
BUG_ON(!hlist_unhashed(&entry->d_alias));
|
|
if (inode)
|
|
spin_lock(&inode->i_lock);
|
|
__d_instantiate(entry, inode);
|
|
if (inode)
|
|
spin_unlock(&inode->i_lock);
|
|
security_d_instantiate(entry, inode);
|
|
}
|
|
EXPORT_SYMBOL(d_instantiate);
|
|
|
|
/**
|
|
* d_instantiate_unique - instantiate a non-aliased dentry
|
|
* @entry: dentry to instantiate
|
|
* @inode: inode to attach to this dentry
|
|
*
|
|
* Fill in inode information in the entry. On success, it returns NULL.
|
|
* If an unhashed alias of "entry" already exists, then we return the
|
|
* aliased dentry instead and drop one reference to inode.
|
|
*
|
|
* Note that in order to avoid conflicts with rename() etc, the caller
|
|
* had better be holding the parent directory semaphore.
|
|
*
|
|
* This also assumes that the inode count has been incremented
|
|
* (or otherwise set) by the caller to indicate that it is now
|
|
* in use by the dcache.
|
|
*/
|
|
static struct dentry *__d_instantiate_unique(struct dentry *entry,
|
|
struct inode *inode)
|
|
{
|
|
struct dentry *alias;
|
|
int len = entry->d_name.len;
|
|
const char *name = entry->d_name.name;
|
|
unsigned int hash = entry->d_name.hash;
|
|
|
|
if (!inode) {
|
|
__d_instantiate(entry, NULL);
|
|
return NULL;
|
|
}
|
|
|
|
hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
|
|
/*
|
|
* Don't need alias->d_lock here, because aliases with
|
|
* d_parent == entry->d_parent are not subject to name or
|
|
* parent changes, because the parent inode i_mutex is held.
|
|
*/
|
|
if (alias->d_name.hash != hash)
|
|
continue;
|
|
if (alias->d_parent != entry->d_parent)
|
|
continue;
|
|
if (alias->d_name.len != len)
|
|
continue;
|
|
if (dentry_cmp(alias, name, len))
|
|
continue;
|
|
__dget(alias);
|
|
return alias;
|
|
}
|
|
|
|
__d_instantiate(entry, inode);
|
|
return NULL;
|
|
}
|
|
|
|
struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
|
|
{
|
|
struct dentry *result;
|
|
|
|
BUG_ON(!hlist_unhashed(&entry->d_alias));
|
|
|
|
if (inode)
|
|
spin_lock(&inode->i_lock);
|
|
result = __d_instantiate_unique(entry, inode);
|
|
if (inode)
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
if (!result) {
|
|
security_d_instantiate(entry, inode);
|
|
return NULL;
|
|
}
|
|
|
|
BUG_ON(!d_unhashed(result));
|
|
iput(inode);
|
|
return result;
|
|
}
|
|
|
|
EXPORT_SYMBOL(d_instantiate_unique);
|
|
|
|
struct dentry *d_make_root(struct inode *root_inode)
|
|
{
|
|
struct dentry *res = NULL;
|
|
|
|
if (root_inode) {
|
|
static const struct qstr name = QSTR_INIT("/", 1);
|
|
|
|
res = __d_alloc(root_inode->i_sb, &name);
|
|
if (res)
|
|
d_instantiate(res, root_inode);
|
|
else
|
|
iput(root_inode);
|
|
}
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(d_make_root);
|
|
|
|
static struct dentry * __d_find_any_alias(struct inode *inode)
|
|
{
|
|
struct dentry *alias;
|
|
|
|
if (hlist_empty(&inode->i_dentry))
|
|
return NULL;
|
|
alias = hlist_entry(inode->i_dentry.first, struct dentry, d_alias);
|
|
__dget(alias);
|
|
return alias;
|
|
}
|
|
|
|
/**
|
|
* d_find_any_alias - find any alias for a given inode
|
|
* @inode: inode to find an alias for
|
|
*
|
|
* If any aliases exist for the given inode, take and return a
|
|
* reference for one of them. If no aliases exist, return %NULL.
|
|
*/
|
|
struct dentry *d_find_any_alias(struct inode *inode)
|
|
{
|
|
struct dentry *de;
|
|
|
|
spin_lock(&inode->i_lock);
|
|
de = __d_find_any_alias(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
return de;
|
|
}
|
|
EXPORT_SYMBOL(d_find_any_alias);
|
|
|
|
/**
|
|
* d_obtain_alias - find or allocate a dentry for a given inode
|
|
* @inode: inode to allocate the dentry for
|
|
*
|
|
* Obtain a dentry for an inode resulting from NFS filehandle conversion or
|
|
* similar open by handle operations. The returned dentry may be anonymous,
|
|
* or may have a full name (if the inode was already in the cache).
|
|
*
|
|
* When called on a directory inode, we must ensure that the inode only ever
|
|
* has one dentry. If a dentry is found, that is returned instead of
|
|
* allocating a new one.
|
|
*
|
|
* On successful return, the reference to the inode has been transferred
|
|
* to the dentry. In case of an error the reference on the inode is released.
|
|
* To make it easier to use in export operations a %NULL or IS_ERR inode may
|
|
* be passed in and will be the error will be propagate to the return value,
|
|
* with a %NULL @inode replaced by ERR_PTR(-ESTALE).
|
|
*/
|
|
struct dentry *d_obtain_alias(struct inode *inode)
|
|
{
|
|
static const struct qstr anonstring = QSTR_INIT("/", 1);
|
|
struct dentry *tmp;
|
|
struct dentry *res;
|
|
|
|
if (!inode)
|
|
return ERR_PTR(-ESTALE);
|
|
if (IS_ERR(inode))
|
|
return ERR_CAST(inode);
|
|
|
|
res = d_find_any_alias(inode);
|
|
if (res)
|
|
goto out_iput;
|
|
|
|
tmp = __d_alloc(inode->i_sb, &anonstring);
|
|
if (!tmp) {
|
|
res = ERR_PTR(-ENOMEM);
|
|
goto out_iput;
|
|
}
|
|
|
|
spin_lock(&inode->i_lock);
|
|
res = __d_find_any_alias(inode);
|
|
if (res) {
|
|
spin_unlock(&inode->i_lock);
|
|
dput(tmp);
|
|
goto out_iput;
|
|
}
|
|
|
|
/* attach a disconnected dentry */
|
|
spin_lock(&tmp->d_lock);
|
|
tmp->d_inode = inode;
|
|
tmp->d_flags |= DCACHE_DISCONNECTED;
|
|
hlist_add_head(&tmp->d_alias, &inode->i_dentry);
|
|
hlist_bl_lock(&tmp->d_sb->s_anon);
|
|
hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
|
|
hlist_bl_unlock(&tmp->d_sb->s_anon);
|
|
spin_unlock(&tmp->d_lock);
|
|
spin_unlock(&inode->i_lock);
|
|
security_d_instantiate(tmp, inode);
|
|
|
|
return tmp;
|
|
|
|
out_iput:
|
|
if (res && !IS_ERR(res))
|
|
security_d_instantiate(res, inode);
|
|
iput(inode);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(d_obtain_alias);
|
|
|
|
/**
|
|
* d_splice_alias - splice a disconnected dentry into the tree if one exists
|
|
* @inode: the inode which may have a disconnected dentry
|
|
* @dentry: a negative dentry which we want to point to the inode.
|
|
*
|
|
* If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
|
|
* DCACHE_DISCONNECTED), then d_move that in place of the given dentry
|
|
* and return it, else simply d_add the inode to the dentry and return NULL.
|
|
*
|
|
* This is needed in the lookup routine of any filesystem that is exportable
|
|
* (via knfsd) so that we can build dcache paths to directories effectively.
|
|
*
|
|
* If a dentry was found and moved, then it is returned. Otherwise NULL
|
|
* is returned. This matches the expected return value of ->lookup.
|
|
*
|
|
* Cluster filesystems may call this function with a negative, hashed dentry.
|
|
* In that case, we know that the inode will be a regular file, and also this
|
|
* will only occur during atomic_open. So we need to check for the dentry
|
|
* being already hashed only in the final case.
|
|
*/
|
|
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
|
|
{
|
|
struct dentry *new = NULL;
|
|
|
|
if (IS_ERR(inode))
|
|
return ERR_CAST(inode);
|
|
|
|
if (inode && S_ISDIR(inode->i_mode)) {
|
|
spin_lock(&inode->i_lock);
|
|
new = __d_find_alias(inode, 1);
|
|
if (new) {
|
|
BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
|
|
spin_unlock(&inode->i_lock);
|
|
security_d_instantiate(new, inode);
|
|
d_move(new, dentry);
|
|
iput(inode);
|
|
} else {
|
|
/* already taking inode->i_lock, so d_add() by hand */
|
|
__d_instantiate(dentry, inode);
|
|
spin_unlock(&inode->i_lock);
|
|
security_d_instantiate(dentry, inode);
|
|
d_rehash(dentry);
|
|
}
|
|
} else {
|
|
d_instantiate(dentry, inode);
|
|
if (d_unhashed(dentry))
|
|
d_rehash(dentry);
|
|
}
|
|
return new;
|
|
}
|
|
EXPORT_SYMBOL(d_splice_alias);
|
|
|
|
/**
|
|
* d_add_ci - lookup or allocate new dentry with case-exact name
|
|
* @inode: the inode case-insensitive lookup has found
|
|
* @dentry: the negative dentry that was passed to the parent's lookup func
|
|
* @name: the case-exact name to be associated with the returned dentry
|
|
*
|
|
* This is to avoid filling the dcache with case-insensitive names to the
|
|
* same inode, only the actual correct case is stored in the dcache for
|
|
* case-insensitive filesystems.
|
|
*
|
|
* For a case-insensitive lookup match and if the the case-exact dentry
|
|
* already exists in in the dcache, use it and return it.
|
|
*
|
|
* If no entry exists with the exact case name, allocate new dentry with
|
|
* the exact case, and return the spliced entry.
|
|
*/
|
|
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
|
|
struct qstr *name)
|
|
{
|
|
struct dentry *found;
|
|
struct dentry *new;
|
|
|
|
/*
|
|
* First check if a dentry matching the name already exists,
|
|
* if not go ahead and create it now.
|
|
*/
|
|
found = d_hash_and_lookup(dentry->d_parent, name);
|
|
if (unlikely(IS_ERR(found)))
|
|
goto err_out;
|
|
if (!found) {
|
|
new = d_alloc(dentry->d_parent, name);
|
|
if (!new) {
|
|
found = ERR_PTR(-ENOMEM);
|
|
goto err_out;
|
|
}
|
|
|
|
found = d_splice_alias(inode, new);
|
|
if (found) {
|
|
dput(new);
|
|
return found;
|
|
}
|
|
return new;
|
|
}
|
|
|
|
/*
|
|
* If a matching dentry exists, and it's not negative use it.
|
|
*
|
|
* Decrement the reference count to balance the iget() done
|
|
* earlier on.
|
|
*/
|
|
if (found->d_inode) {
|
|
if (unlikely(found->d_inode != inode)) {
|
|
/* This can't happen because bad inodes are unhashed. */
|
|
BUG_ON(!is_bad_inode(inode));
|
|
BUG_ON(!is_bad_inode(found->d_inode));
|
|
}
|
|
iput(inode);
|
|
return found;
|
|
}
|
|
|
|
/*
|
|
* Negative dentry: instantiate it unless the inode is a directory and
|
|
* already has a dentry.
|
|
*/
|
|
new = d_splice_alias(inode, found);
|
|
if (new) {
|
|
dput(found);
|
|
found = new;
|
|
}
|
|
return found;
|
|
|
|
err_out:
|
|
iput(inode);
|
|
return found;
|
|
}
|
|
EXPORT_SYMBOL(d_add_ci);
|
|
|
|
/*
|
|
* Do the slow-case of the dentry name compare.
|
|
*
|
|
* Unlike the dentry_cmp() function, we need to atomically
|
|
* load the name and length information, so that the
|
|
* filesystem can rely on them, and can use the 'name' and
|
|
* 'len' information without worrying about walking off the
|
|
* end of memory etc.
|
|
*
|
|
* Thus the read_seqcount_retry() and the "duplicate" info
|
|
* in arguments (the low-level filesystem should not look
|
|
* at the dentry inode or name contents directly, since
|
|
* rename can change them while we're in RCU mode).
|
|
*/
|
|
enum slow_d_compare {
|
|
D_COMP_OK,
|
|
D_COMP_NOMATCH,
|
|
D_COMP_SEQRETRY,
|
|
};
|
|
|
|
static noinline enum slow_d_compare slow_dentry_cmp(
|
|
const struct dentry *parent,
|
|
struct dentry *dentry,
|
|
unsigned int seq,
|
|
const struct qstr *name)
|
|
{
|
|
int tlen = dentry->d_name.len;
|
|
const char *tname = dentry->d_name.name;
|
|
|
|
if (read_seqcount_retry(&dentry->d_seq, seq)) {
|
|
cpu_relax();
|
|
return D_COMP_SEQRETRY;
|
|
}
|
|
if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
|
|
return D_COMP_NOMATCH;
|
|
return D_COMP_OK;
|
|
}
|
|
|
|
/**
|
|
* __d_lookup_rcu - search for a dentry (racy, store-free)
|
|
* @parent: parent dentry
|
|
* @name: qstr of name we wish to find
|
|
* @seqp: returns d_seq value at the point where the dentry was found
|
|
* Returns: dentry, or NULL
|
|
*
|
|
* __d_lookup_rcu is the dcache lookup function for rcu-walk name
|
|
* resolution (store-free path walking) design described in
|
|
* Documentation/filesystems/path-lookup.txt.
|
|
*
|
|
* This is not to be used outside core vfs.
|
|
*
|
|
* __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
|
|
* held, and rcu_read_lock held. The returned dentry must not be stored into
|
|
* without taking d_lock and checking d_seq sequence count against @seq
|
|
* returned here.
|
|
*
|
|
* A refcount may be taken on the found dentry with the d_rcu_to_refcount
|
|
* function.
|
|
*
|
|
* Alternatively, __d_lookup_rcu may be called again to look up the child of
|
|
* the returned dentry, so long as its parent's seqlock is checked after the
|
|
* child is looked up. Thus, an interlocking stepping of sequence lock checks
|
|
* is formed, giving integrity down the path walk.
|
|
*
|
|
* NOTE! The caller *has* to check the resulting dentry against the sequence
|
|
* number we've returned before using any of the resulting dentry state!
|
|
*/
|
|
struct dentry *__d_lookup_rcu(const struct dentry *parent,
|
|
const struct qstr *name,
|
|
unsigned *seqp)
|
|
{
|
|
u64 hashlen = name->hash_len;
|
|
const unsigned char *str = name->name;
|
|
struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen));
|
|
struct hlist_bl_node *node;
|
|
struct dentry *dentry;
|
|
|
|
/*
|
|
* Note: There is significant duplication with __d_lookup_rcu which is
|
|
* required to prevent single threaded performance regressions
|
|
* especially on architectures where smp_rmb (in seqcounts) are costly.
|
|
* Keep the two functions in sync.
|
|
*/
|
|
|
|
/*
|
|
* The hash list is protected using RCU.
|
|
*
|
|
* Carefully use d_seq when comparing a candidate dentry, to avoid
|
|
* races with d_move().
|
|
*
|
|
* It is possible that concurrent renames can mess up our list
|
|
* walk here and result in missing our dentry, resulting in the
|
|
* false-negative result. d_lookup() protects against concurrent
|
|
* renames using rename_lock seqlock.
|
|
*
|
|
* See Documentation/filesystems/path-lookup.txt for more details.
|
|
*/
|
|
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
|
|
unsigned seq;
|
|
|
|
seqretry:
|
|
/*
|
|
* The dentry sequence count protects us from concurrent
|
|
* renames, and thus protects parent and name fields.
|
|
*
|
|
* The caller must perform a seqcount check in order
|
|
* to do anything useful with the returned dentry.
|
|
*
|
|
* NOTE! We do a "raw" seqcount_begin here. That means that
|
|
* we don't wait for the sequence count to stabilize if it
|
|
* is in the middle of a sequence change. If we do the slow
|
|
* dentry compare, we will do seqretries until it is stable,
|
|
* and if we end up with a successful lookup, we actually
|
|
* want to exit RCU lookup anyway.
|
|
*/
|
|
seq = raw_seqcount_begin(&dentry->d_seq);
|
|
if (dentry->d_parent != parent)
|
|
continue;
|
|
if (d_unhashed(dentry))
|
|
continue;
|
|
|
|
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
|
|
if (dentry->d_name.hash != hashlen_hash(hashlen))
|
|
continue;
|
|
*seqp = seq;
|
|
switch (slow_dentry_cmp(parent, dentry, seq, name)) {
|
|
case D_COMP_OK:
|
|
return dentry;
|
|
case D_COMP_NOMATCH:
|
|
continue;
|
|
default:
|
|
goto seqretry;
|
|
}
|
|
}
|
|
|
|
if (dentry->d_name.hash_len != hashlen)
|
|
continue;
|
|
*seqp = seq;
|
|
if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
|
|
return dentry;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* d_lookup - search for a dentry
|
|
* @parent: parent dentry
|
|
* @name: qstr of name we wish to find
|
|
* Returns: dentry, or NULL
|
|
*
|
|
* d_lookup searches the children of the parent dentry for the name in
|
|
* question. If the dentry is found its reference count is incremented and the
|
|
* dentry is returned. The caller must use dput to free the entry when it has
|
|
* finished using it. %NULL is returned if the dentry does not exist.
|
|
*/
|
|
struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
|
|
{
|
|
struct dentry *dentry;
|
|
unsigned seq;
|
|
|
|
do {
|
|
seq = read_seqbegin(&rename_lock);
|
|
dentry = __d_lookup(parent, name);
|
|
if (dentry)
|
|
break;
|
|
} while (read_seqretry(&rename_lock, seq));
|
|
return dentry;
|
|
}
|
|
EXPORT_SYMBOL(d_lookup);
|
|
|
|
/**
|
|
* __d_lookup - search for a dentry (racy)
|
|
* @parent: parent dentry
|
|
* @name: qstr of name we wish to find
|
|
* Returns: dentry, or NULL
|
|
*
|
|
* __d_lookup is like d_lookup, however it may (rarely) return a
|
|
* false-negative result due to unrelated rename activity.
|
|
*
|
|
* __d_lookup is slightly faster by avoiding rename_lock read seqlock,
|
|
* however it must be used carefully, eg. with a following d_lookup in
|
|
* the case of failure.
|
|
*
|
|
* __d_lookup callers must be commented.
|
|
*/
|
|
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
|
|
{
|
|
unsigned int len = name->len;
|
|
unsigned int hash = name->hash;
|
|
const unsigned char *str = name->name;
|
|
struct hlist_bl_head *b = d_hash(parent, hash);
|
|
struct hlist_bl_node *node;
|
|
struct dentry *found = NULL;
|
|
struct dentry *dentry;
|
|
|
|
/*
|
|
* Note: There is significant duplication with __d_lookup_rcu which is
|
|
* required to prevent single threaded performance regressions
|
|
* especially on architectures where smp_rmb (in seqcounts) are costly.
|
|
* Keep the two functions in sync.
|
|
*/
|
|
|
|
/*
|
|
* The hash list is protected using RCU.
|
|
*
|
|
* Take d_lock when comparing a candidate dentry, to avoid races
|
|
* with d_move().
|
|
*
|
|
* It is possible that concurrent renames can mess up our list
|
|
* walk here and result in missing our dentry, resulting in the
|
|
* false-negative result. d_lookup() protects against concurrent
|
|
* renames using rename_lock seqlock.
|
|
*
|
|
* See Documentation/filesystems/path-lookup.txt for more details.
|
|
*/
|
|
rcu_read_lock();
|
|
|
|
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
|
|
|
|
if (dentry->d_name.hash != hash)
|
|
continue;
|
|
|
|
spin_lock(&dentry->d_lock);
|
|
if (dentry->d_parent != parent)
|
|
goto next;
|
|
if (d_unhashed(dentry))
|
|
goto next;
|
|
|
|
/*
|
|
* It is safe to compare names since d_move() cannot
|
|
* change the qstr (protected by d_lock).
|
|
*/
|
|
if (parent->d_flags & DCACHE_OP_COMPARE) {
|
|
int tlen = dentry->d_name.len;
|
|
const char *tname = dentry->d_name.name;
|
|
if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
|
|
goto next;
|
|
} else {
|
|
if (dentry->d_name.len != len)
|
|
goto next;
|
|
if (dentry_cmp(dentry, str, len))
|
|
goto next;
|
|
}
|
|
|
|
dentry->d_lockref.count++;
|
|
found = dentry;
|
|
spin_unlock(&dentry->d_lock);
|
|
break;
|
|
next:
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return found;
|
|
}
|
|
|
|
/**
|
|
* d_hash_and_lookup - hash the qstr then search for a dentry
|
|
* @dir: Directory to search in
|
|
* @name: qstr of name we wish to find
|
|
*
|
|
* On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
|
|
*/
|
|
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
|
|
{
|
|
/*
|
|
* Check for a fs-specific hash function. Note that we must
|
|
* calculate the standard hash first, as the d_op->d_hash()
|
|
* routine may choose to leave the hash value unchanged.
|
|
*/
|
|
name->hash = full_name_hash(name->name, name->len);
|
|
if (dir->d_flags & DCACHE_OP_HASH) {
|
|
int err = dir->d_op->d_hash(dir, name);
|
|
if (unlikely(err < 0))
|
|
return ERR_PTR(err);
|
|
}
|
|
return d_lookup(dir, name);
|
|
}
|
|
EXPORT_SYMBOL(d_hash_and_lookup);
|
|
|
|
/**
|
|
* d_validate - verify dentry provided from insecure source (deprecated)
|
|
* @dentry: The dentry alleged to be valid child of @dparent
|
|
* @dparent: The parent dentry (known to be valid)
|
|
*
|
|
* An insecure source has sent us a dentry, here we verify it and dget() it.
|
|
* This is used by ncpfs in its readdir implementation.
|
|
* Zero is returned in the dentry is invalid.
|
|
*
|
|
* This function is slow for big directories, and deprecated, do not use it.
|
|
*/
|
|
int d_validate(struct dentry *dentry, struct dentry *dparent)
|
|
{
|
|
struct dentry *child;
|
|
|
|
spin_lock(&dparent->d_lock);
|
|
list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
|
|
if (dentry == child) {
|
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
|
|
__dget_dlock(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
spin_unlock(&dparent->d_lock);
|
|
return 1;
|
|
}
|
|
}
|
|
spin_unlock(&dparent->d_lock);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(d_validate);
|
|
|
|
/*
|
|
* When a file is deleted, we have two options:
|
|
* - turn this dentry into a negative dentry
|
|
* - unhash this dentry and free it.
|
|
*
|
|
* Usually, we want to just turn this into
|
|
* a negative dentry, but if anybody else is
|
|
* currently using the dentry or the inode
|
|
* we can't do that and we fall back on removing
|
|
* it from the hash queues and waiting for
|
|
* it to be deleted later when it has no users
|
|
*/
|
|
|
|
/**
|
|
* d_delete - delete a dentry
|
|
* @dentry: The dentry to delete
|
|
*
|
|
* Turn the dentry into a negative dentry if possible, otherwise
|
|
* remove it from the hash queues so it can be deleted later
|
|
*/
|
|
|
|
void d_delete(struct dentry * dentry)
|
|
{
|
|
struct inode *inode;
|
|
int isdir = 0;
|
|
/*
|
|
* Are we the only user?
|
|
*/
|
|
again:
|
|
spin_lock(&dentry->d_lock);
|
|
inode = dentry->d_inode;
|
|
isdir = S_ISDIR(inode->i_mode);
|
|
if (dentry->d_lockref.count == 1) {
|
|
if (!spin_trylock(&inode->i_lock)) {
|
|
spin_unlock(&dentry->d_lock);
|
|
cpu_relax();
|
|
goto again;
|
|
}
|
|
dentry->d_flags &= ~DCACHE_CANT_MOUNT;
|
|
dentry_unlink_inode(dentry);
|
|
fsnotify_nameremove(dentry, isdir);
|
|
return;
|
|
}
|
|
|
|
if (!d_unhashed(dentry))
|
|
__d_drop(dentry);
|
|
|
|
spin_unlock(&dentry->d_lock);
|
|
|
|
fsnotify_nameremove(dentry, isdir);
|
|
}
|
|
EXPORT_SYMBOL(d_delete);
|
|
|
|
static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
|
|
{
|
|
BUG_ON(!d_unhashed(entry));
|
|
hlist_bl_lock(b);
|
|
entry->d_flags |= DCACHE_RCUACCESS;
|
|
hlist_bl_add_head_rcu(&entry->d_hash, b);
|
|
hlist_bl_unlock(b);
|
|
}
|
|
|
|
static void _d_rehash(struct dentry * entry)
|
|
{
|
|
__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
|
|
}
|
|
|
|
/**
|
|
* d_rehash - add an entry back to the hash
|
|
* @entry: dentry to add to the hash
|
|
*
|
|
* Adds a dentry to the hash according to its name.
|
|
*/
|
|
|
|
void d_rehash(struct dentry * entry)
|
|
{
|
|
spin_lock(&entry->d_lock);
|
|
_d_rehash(entry);
|
|
spin_unlock(&entry->d_lock);
|
|
}
|
|
EXPORT_SYMBOL(d_rehash);
|
|
|
|
/**
|
|
* dentry_update_name_case - update case insensitive dentry with a new name
|
|
* @dentry: dentry to be updated
|
|
* @name: new name
|
|
*
|
|
* Update a case insensitive dentry with new case of name.
|
|
*
|
|
* dentry must have been returned by d_lookup with name @name. Old and new
|
|
* name lengths must match (ie. no d_compare which allows mismatched name
|
|
* lengths).
|
|
*
|
|
* Parent inode i_mutex must be held over d_lookup and into this call (to
|
|
* keep renames and concurrent inserts, and readdir(2) away).
|
|
*/
|
|
void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
|
|
{
|
|
BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
|
|
BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
|
|
|
|
spin_lock(&dentry->d_lock);
|
|
write_seqcount_begin(&dentry->d_seq);
|
|
memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
|
|
write_seqcount_end(&dentry->d_seq);
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
EXPORT_SYMBOL(dentry_update_name_case);
|
|
|
|
static void switch_names(struct dentry *dentry, struct dentry *target)
|
|
{
|
|
if (dname_external(target)) {
|
|
if (dname_external(dentry)) {
|
|
/*
|
|
* Both external: swap the pointers
|
|
*/
|
|
swap(target->d_name.name, dentry->d_name.name);
|
|
} else {
|
|
/*
|
|
* dentry:internal, target:external. Steal target's
|
|
* storage and make target internal.
|
|
*/
|
|
memcpy(target->d_iname, dentry->d_name.name,
|
|
dentry->d_name.len + 1);
|
|
dentry->d_name.name = target->d_name.name;
|
|
target->d_name.name = target->d_iname;
|
|
}
|
|
} else {
|
|
if (dname_external(dentry)) {
|
|
/*
|
|
* dentry:external, target:internal. Give dentry's
|
|
* storage to target and make dentry internal
|
|
*/
|
|
memcpy(dentry->d_iname, target->d_name.name,
|
|
target->d_name.len + 1);
|
|
target->d_name.name = dentry->d_name.name;
|
|
dentry->d_name.name = dentry->d_iname;
|
|
} else {
|
|
/*
|
|
* Both are internal. Just copy target to dentry
|
|
*/
|
|
memcpy(dentry->d_iname, target->d_name.name,
|
|
target->d_name.len + 1);
|
|
dentry->d_name.len = target->d_name.len;
|
|
return;
|
|
}
|
|
}
|
|
swap(dentry->d_name.len, target->d_name.len);
|
|
}
|
|
|
|
static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
|
|
{
|
|
/*
|
|
* XXXX: do we really need to take target->d_lock?
|
|
*/
|
|
if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
|
|
spin_lock(&target->d_parent->d_lock);
|
|
else {
|
|
if (d_ancestor(dentry->d_parent, target->d_parent)) {
|
|
spin_lock(&dentry->d_parent->d_lock);
|
|
spin_lock_nested(&target->d_parent->d_lock,
|
|
DENTRY_D_LOCK_NESTED);
|
|
} else {
|
|
spin_lock(&target->d_parent->d_lock);
|
|
spin_lock_nested(&dentry->d_parent->d_lock,
|
|
DENTRY_D_LOCK_NESTED);
|
|
}
|
|
}
|
|
if (target < dentry) {
|
|
spin_lock_nested(&target->d_lock, 2);
|
|
spin_lock_nested(&dentry->d_lock, 3);
|
|
} else {
|
|
spin_lock_nested(&dentry->d_lock, 2);
|
|
spin_lock_nested(&target->d_lock, 3);
|
|
}
|
|
}
|
|
|
|
static void dentry_unlock_parents_for_move(struct dentry *dentry,
|
|
struct dentry *target)
|
|
{
|
|
if (target->d_parent != dentry->d_parent)
|
|
spin_unlock(&dentry->d_parent->d_lock);
|
|
if (target->d_parent != target)
|
|
spin_unlock(&target->d_parent->d_lock);
|
|
}
|
|
|
|
/*
|
|
* When switching names, the actual string doesn't strictly have to
|
|
* be preserved in the target - because we're dropping the target
|
|
* anyway. As such, we can just do a simple memcpy() to copy over
|
|
* the new name before we switch.
|
|
*
|
|
* Note that we have to be a lot more careful about getting the hash
|
|
* switched - we have to switch the hash value properly even if it
|
|
* then no longer matches the actual (corrupted) string of the target.
|
|
* The hash value has to match the hash queue that the dentry is on..
|
|
*/
|
|
/*
|
|
* __d_move - move a dentry
|
|
* @dentry: entry to move
|
|
* @target: new dentry
|
|
*
|
|
* Update the dcache to reflect the move of a file name. Negative
|
|
* dcache entries should not be moved in this way. Caller must hold
|
|
* rename_lock, the i_mutex of the source and target directories,
|
|
* and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
|
|
*/
|
|
static void __d_move(struct dentry * dentry, struct dentry * target)
|
|
{
|
|
if (!dentry->d_inode)
|
|
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
|
|
|
|
BUG_ON(d_ancestor(dentry, target));
|
|
BUG_ON(d_ancestor(target, dentry));
|
|
|
|
dentry_lock_for_move(dentry, target);
|
|
|
|
write_seqcount_begin(&dentry->d_seq);
|
|
write_seqcount_begin(&target->d_seq);
|
|
|
|
/* __d_drop does write_seqcount_barrier, but they're OK to nest. */
|
|
|
|
/*
|
|
* Move the dentry to the target hash queue. Don't bother checking
|
|
* for the same hash queue because of how unlikely it is.
|
|
*/
|
|
__d_drop(dentry);
|
|
__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
|
|
|
|
/* Unhash the target: dput() will then get rid of it */
|
|
__d_drop(target);
|
|
|
|
list_del(&dentry->d_u.d_child);
|
|
list_del(&target->d_u.d_child);
|
|
|
|
/* Switch the names.. */
|
|
switch_names(dentry, target);
|
|
swap(dentry->d_name.hash, target->d_name.hash);
|
|
|
|
/* ... and switch the parents */
|
|
if (IS_ROOT(dentry)) {
|
|
dentry->d_parent = target->d_parent;
|
|
target->d_parent = target;
|
|
INIT_LIST_HEAD(&target->d_u.d_child);
|
|
} else {
|
|
swap(dentry->d_parent, target->d_parent);
|
|
|
|
/* And add them back to the (new) parent lists */
|
|
list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
|
|
}
|
|
|
|
list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
|
|
|
|
write_seqcount_end(&target->d_seq);
|
|
write_seqcount_end(&dentry->d_seq);
|
|
|
|
dentry_unlock_parents_for_move(dentry, target);
|
|
spin_unlock(&target->d_lock);
|
|
fsnotify_d_move(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
|
|
/*
|
|
* d_move - move a dentry
|
|
* @dentry: entry to move
|
|
* @target: new dentry
|
|
*
|
|
* Update the dcache to reflect the move of a file name. Negative
|
|
* dcache entries should not be moved in this way. See the locking
|
|
* requirements for __d_move.
|
|
*/
|
|
void d_move(struct dentry *dentry, struct dentry *target)
|
|
{
|
|
write_seqlock(&rename_lock);
|
|
__d_move(dentry, target);
|
|
write_sequnlock(&rename_lock);
|
|
}
|
|
EXPORT_SYMBOL(d_move);
|
|
|
|
/**
|
|
* d_ancestor - search for an ancestor
|
|
* @p1: ancestor dentry
|
|
* @p2: child dentry
|
|
*
|
|
* Returns the ancestor dentry of p2 which is a child of p1, if p1 is
|
|
* an ancestor of p2, else NULL.
|
|
*/
|
|
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
|
|
{
|
|
struct dentry *p;
|
|
|
|
for (p = p2; !IS_ROOT(p); p = p->d_parent) {
|
|
if (p->d_parent == p1)
|
|
return p;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* This helper attempts to cope with remotely renamed directories
|
|
*
|
|
* It assumes that the caller is already holding
|
|
* dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
|
|
*
|
|
* Note: If ever the locking in lock_rename() changes, then please
|
|
* remember to update this too...
|
|
*/
|
|
static struct dentry *__d_unalias(struct inode *inode,
|
|
struct dentry *dentry, struct dentry *alias)
|
|
{
|
|
struct mutex *m1 = NULL, *m2 = NULL;
|
|
struct dentry *ret = ERR_PTR(-EBUSY);
|
|
|
|
/* If alias and dentry share a parent, then no extra locks required */
|
|
if (alias->d_parent == dentry->d_parent)
|
|
goto out_unalias;
|
|
|
|
/* See lock_rename() */
|
|
if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
|
|
goto out_err;
|
|
m1 = &dentry->d_sb->s_vfs_rename_mutex;
|
|
if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
|
|
goto out_err;
|
|
m2 = &alias->d_parent->d_inode->i_mutex;
|
|
out_unalias:
|
|
if (likely(!d_mountpoint(alias))) {
|
|
__d_move(alias, dentry);
|
|
ret = alias;
|
|
}
|
|
out_err:
|
|
spin_unlock(&inode->i_lock);
|
|
if (m2)
|
|
mutex_unlock(m2);
|
|
if (m1)
|
|
mutex_unlock(m1);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Prepare an anonymous dentry for life in the superblock's dentry tree as a
|
|
* named dentry in place of the dentry to be replaced.
|
|
* returns with anon->d_lock held!
|
|
*/
|
|
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
|
|
{
|
|
struct dentry *dparent;
|
|
|
|
dentry_lock_for_move(anon, dentry);
|
|
|
|
write_seqcount_begin(&dentry->d_seq);
|
|
write_seqcount_begin(&anon->d_seq);
|
|
|
|
dparent = dentry->d_parent;
|
|
|
|
switch_names(dentry, anon);
|
|
swap(dentry->d_name.hash, anon->d_name.hash);
|
|
|
|
dentry->d_parent = dentry;
|
|
list_del_init(&dentry->d_u.d_child);
|
|
anon->d_parent = dparent;
|
|
list_move(&anon->d_u.d_child, &dparent->d_subdirs);
|
|
|
|
write_seqcount_end(&dentry->d_seq);
|
|
write_seqcount_end(&anon->d_seq);
|
|
|
|
dentry_unlock_parents_for_move(anon, dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
|
|
/* anon->d_lock still locked, returns locked */
|
|
anon->d_flags &= ~DCACHE_DISCONNECTED;
|
|
}
|
|
|
|
/**
|
|
* d_materialise_unique - introduce an inode into the tree
|
|
* @dentry: candidate dentry
|
|
* @inode: inode to bind to the dentry, to which aliases may be attached
|
|
*
|
|
* Introduces an dentry into the tree, substituting an extant disconnected
|
|
* root directory alias in its place if there is one. Caller must hold the
|
|
* i_mutex of the parent directory.
|
|
*/
|
|
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
|
|
{
|
|
struct dentry *actual;
|
|
|
|
BUG_ON(!d_unhashed(dentry));
|
|
|
|
if (!inode) {
|
|
actual = dentry;
|
|
__d_instantiate(dentry, NULL);
|
|
d_rehash(actual);
|
|
goto out_nolock;
|
|
}
|
|
|
|
spin_lock(&inode->i_lock);
|
|
|
|
if (S_ISDIR(inode->i_mode)) {
|
|
struct dentry *alias;
|
|
|
|
/* Does an aliased dentry already exist? */
|
|
alias = __d_find_alias(inode, 0);
|
|
if (alias) {
|
|
actual = alias;
|
|
write_seqlock(&rename_lock);
|
|
|
|
if (d_ancestor(alias, dentry)) {
|
|
/* Check for loops */
|
|
actual = ERR_PTR(-ELOOP);
|
|
spin_unlock(&inode->i_lock);
|
|
} else if (IS_ROOT(alias)) {
|
|
/* Is this an anonymous mountpoint that we
|
|
* could splice into our tree? */
|
|
__d_materialise_dentry(dentry, alias);
|
|
write_sequnlock(&rename_lock);
|
|
__d_drop(alias);
|
|
goto found;
|
|
} else {
|
|
/* Nope, but we must(!) avoid directory
|
|
* aliasing. This drops inode->i_lock */
|
|
actual = __d_unalias(inode, dentry, alias);
|
|
}
|
|
write_sequnlock(&rename_lock);
|
|
if (IS_ERR(actual)) {
|
|
if (PTR_ERR(actual) == -ELOOP)
|
|
pr_warn_ratelimited(
|
|
"VFS: Lookup of '%s' in %s %s"
|
|
" would have caused loop\n",
|
|
dentry->d_name.name,
|
|
inode->i_sb->s_type->name,
|
|
inode->i_sb->s_id);
|
|
dput(alias);
|
|
}
|
|
goto out_nolock;
|
|
}
|
|
}
|
|
|
|
/* Add a unique reference */
|
|
actual = __d_instantiate_unique(dentry, inode);
|
|
if (!actual)
|
|
actual = dentry;
|
|
else
|
|
BUG_ON(!d_unhashed(actual));
|
|
|
|
spin_lock(&actual->d_lock);
|
|
found:
|
|
_d_rehash(actual);
|
|
spin_unlock(&actual->d_lock);
|
|
spin_unlock(&inode->i_lock);
|
|
out_nolock:
|
|
if (actual == dentry) {
|
|
security_d_instantiate(dentry, inode);
|
|
return NULL;
|
|
}
|
|
|
|
iput(inode);
|
|
return actual;
|
|
}
|
|
EXPORT_SYMBOL_GPL(d_materialise_unique);
|
|
|
|
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
|
|
{
|
|
*buflen -= namelen;
|
|
if (*buflen < 0)
|
|
return -ENAMETOOLONG;
|
|
*buffer -= namelen;
|
|
memcpy(*buffer, str, namelen);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* prepend_name - prepend a pathname in front of current buffer pointer
|
|
* buffer: buffer pointer
|
|
* buflen: allocated length of the buffer
|
|
* name: name string and length qstr structure
|
|
*
|
|
* With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
|
|
* make sure that either the old or the new name pointer and length are
|
|
* fetched. However, there may be mismatch between length and pointer.
|
|
* The length cannot be trusted, we need to copy it byte-by-byte until
|
|
* the length is reached or a null byte is found. It also prepends "/" at
|
|
* the beginning of the name. The sequence number check at the caller will
|
|
* retry it again when a d_move() does happen. So any garbage in the buffer
|
|
* due to mismatched pointer and length will be discarded.
|
|
*/
|
|
static int prepend_name(char **buffer, int *buflen, struct qstr *name)
|
|
{
|
|
const char *dname = ACCESS_ONCE(name->name);
|
|
u32 dlen = ACCESS_ONCE(name->len);
|
|
char *p;
|
|
|
|
if (*buflen < dlen + 1)
|
|
return -ENAMETOOLONG;
|
|
*buflen -= dlen + 1;
|
|
p = *buffer -= dlen + 1;
|
|
*p++ = '/';
|
|
while (dlen--) {
|
|
char c = *dname++;
|
|
if (!c)
|
|
break;
|
|
*p++ = c;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* prepend_path - Prepend path string to a buffer
|
|
* @path: the dentry/vfsmount to report
|
|
* @root: root vfsmnt/dentry
|
|
* @buffer: pointer to the end of the buffer
|
|
* @buflen: pointer to buffer length
|
|
*
|
|
* The function tries to write out the pathname without taking any lock other
|
|
* than the RCU read lock to make sure that dentries won't go away. It only
|
|
* checks the sequence number of the global rename_lock as any change in the
|
|
* dentry's d_seq will be preceded by changes in the rename_lock sequence
|
|
* number. If the sequence number had been change, it will restart the whole
|
|
* pathname back-tracing sequence again. It performs a total of 3 trials of
|
|
* lockless back-tracing sequences before falling back to take the
|
|
* rename_lock.
|
|
*/
|
|
static int prepend_path(const struct path *path,
|
|
const struct path *root,
|
|
char **buffer, int *buflen)
|
|
{
|
|
struct dentry *dentry = path->dentry;
|
|
struct vfsmount *vfsmnt = path->mnt;
|
|
struct mount *mnt = real_mount(vfsmnt);
|
|
int error = 0;
|
|
unsigned seq = 0;
|
|
char *bptr;
|
|
int blen;
|
|
|
|
rcu_read_lock();
|
|
restart:
|
|
bptr = *buffer;
|
|
blen = *buflen;
|
|
read_seqbegin_or_lock(&rename_lock, &seq);
|
|
while (dentry != root->dentry || vfsmnt != root->mnt) {
|
|
struct dentry * parent;
|
|
|
|
if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
|
|
/* Global root? */
|
|
if (mnt_has_parent(mnt)) {
|
|
dentry = mnt->mnt_mountpoint;
|
|
mnt = mnt->mnt_parent;
|
|
vfsmnt = &mnt->mnt;
|
|
continue;
|
|
}
|
|
/*
|
|
* Filesystems needing to implement special "root names"
|
|
* should do so with ->d_dname()
|
|
*/
|
|
if (IS_ROOT(dentry) &&
|
|
(dentry->d_name.len != 1 ||
|
|
dentry->d_name.name[0] != '/')) {
|
|
WARN(1, "Root dentry has weird name <%.*s>\n",
|
|
(int) dentry->d_name.len,
|
|
dentry->d_name.name);
|
|
}
|
|
if (!error)
|
|
error = is_mounted(vfsmnt) ? 1 : 2;
|
|
break;
|
|
}
|
|
parent = dentry->d_parent;
|
|
prefetch(parent);
|
|
error = prepend_name(&bptr, &blen, &dentry->d_name);
|
|
if (error)
|
|
break;
|
|
|
|
dentry = parent;
|
|
}
|
|
if (!(seq & 1))
|
|
rcu_read_unlock();
|
|
if (need_seqretry(&rename_lock, seq)) {
|
|
seq = 1;
|
|
goto restart;
|
|
}
|
|
done_seqretry(&rename_lock, seq);
|
|
|
|
if (error >= 0 && bptr == *buffer) {
|
|
if (--blen < 0)
|
|
error = -ENAMETOOLONG;
|
|
else
|
|
*--bptr = '/';
|
|
}
|
|
*buffer = bptr;
|
|
*buflen = blen;
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* __d_path - return the path of a dentry
|
|
* @path: the dentry/vfsmount to report
|
|
* @root: root vfsmnt/dentry
|
|
* @buf: buffer to return value in
|
|
* @buflen: buffer length
|
|
*
|
|
* Convert a dentry into an ASCII path name.
|
|
*
|
|
* Returns a pointer into the buffer or an error code if the
|
|
* path was too long.
|
|
*
|
|
* "buflen" should be positive.
|
|
*
|
|
* If the path is not reachable from the supplied root, return %NULL.
|
|
*/
|
|
char *__d_path(const struct path *path,
|
|
const struct path *root,
|
|
char *buf, int buflen)
|
|
{
|
|
char *res = buf + buflen;
|
|
int error;
|
|
|
|
prepend(&res, &buflen, "\0", 1);
|
|
br_read_lock(&vfsmount_lock);
|
|
error = prepend_path(path, root, &res, &buflen);
|
|
br_read_unlock(&vfsmount_lock);
|
|
|
|
if (error < 0)
|
|
return ERR_PTR(error);
|
|
if (error > 0)
|
|
return NULL;
|
|
return res;
|
|
}
|
|
|
|
char *d_absolute_path(const struct path *path,
|
|
char *buf, int buflen)
|
|
{
|
|
struct path root = {};
|
|
char *res = buf + buflen;
|
|
int error;
|
|
|
|
prepend(&res, &buflen, "\0", 1);
|
|
br_read_lock(&vfsmount_lock);
|
|
error = prepend_path(path, &root, &res, &buflen);
|
|
br_read_unlock(&vfsmount_lock);
|
|
|
|
if (error > 1)
|
|
error = -EINVAL;
|
|
if (error < 0)
|
|
return ERR_PTR(error);
|
|
return res;
|
|
}
|
|
|
|
/*
|
|
* same as __d_path but appends "(deleted)" for unlinked files.
|
|
*/
|
|
static int path_with_deleted(const struct path *path,
|
|
const struct path *root,
|
|
char **buf, int *buflen)
|
|
{
|
|
prepend(buf, buflen, "\0", 1);
|
|
if (d_unlinked(path->dentry)) {
|
|
int error = prepend(buf, buflen, " (deleted)", 10);
|
|
if (error)
|
|
return error;
|
|
}
|
|
|
|
return prepend_path(path, root, buf, buflen);
|
|
}
|
|
|
|
static int prepend_unreachable(char **buffer, int *buflen)
|
|
{
|
|
return prepend(buffer, buflen, "(unreachable)", 13);
|
|
}
|
|
|
|
/**
|
|
* d_path - return the path of a dentry
|
|
* @path: path to report
|
|
* @buf: buffer to return value in
|
|
* @buflen: buffer length
|
|
*
|
|
* Convert a dentry into an ASCII path name. If the entry has been deleted
|
|
* the string " (deleted)" is appended. Note that this is ambiguous.
|
|
*
|
|
* Returns a pointer into the buffer or an error code if the path was
|
|
* too long. Note: Callers should use the returned pointer, not the passed
|
|
* in buffer, to use the name! The implementation often starts at an offset
|
|
* into the buffer, and may leave 0 bytes at the start.
|
|
*
|
|
* "buflen" should be positive.
|
|
*/
|
|
char *d_path(const struct path *path, char *buf, int buflen)
|
|
{
|
|
char *res = buf + buflen;
|
|
struct path root;
|
|
int error;
|
|
|
|
/*
|
|
* We have various synthetic filesystems that never get mounted. On
|
|
* these filesystems dentries are never used for lookup purposes, and
|
|
* thus don't need to be hashed. They also don't need a name until a
|
|
* user wants to identify the object in /proc/pid/fd/. The little hack
|
|
* below allows us to generate a name for these objects on demand:
|
|
*/
|
|
if (path->dentry->d_op && path->dentry->d_op->d_dname)
|
|
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
|
|
|
|
get_fs_root(current->fs, &root);
|
|
br_read_lock(&vfsmount_lock);
|
|
error = path_with_deleted(path, &root, &res, &buflen);
|
|
br_read_unlock(&vfsmount_lock);
|
|
if (error < 0)
|
|
res = ERR_PTR(error);
|
|
path_put(&root);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(d_path);
|
|
|
|
/*
|
|
* Helper function for dentry_operations.d_dname() members
|
|
*/
|
|
char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
|
|
const char *fmt, ...)
|
|
{
|
|
va_list args;
|
|
char temp[64];
|
|
int sz;
|
|
|
|
va_start(args, fmt);
|
|
sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
|
|
va_end(args);
|
|
|
|
if (sz > sizeof(temp) || sz > buflen)
|
|
return ERR_PTR(-ENAMETOOLONG);
|
|
|
|
buffer += buflen - sz;
|
|
return memcpy(buffer, temp, sz);
|
|
}
|
|
|
|
char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
|
|
{
|
|
char *end = buffer + buflen;
|
|
/* these dentries are never renamed, so d_lock is not needed */
|
|
if (prepend(&end, &buflen, " (deleted)", 11) ||
|
|
prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
|
|
prepend(&end, &buflen, "/", 1))
|
|
end = ERR_PTR(-ENAMETOOLONG);
|
|
return end;
|
|
}
|
|
|
|
/*
|
|
* Write full pathname from the root of the filesystem into the buffer.
|
|
*/
|
|
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
|
|
{
|
|
char *end, *retval;
|
|
int len, seq = 0;
|
|
int error = 0;
|
|
|
|
rcu_read_lock();
|
|
restart:
|
|
end = buf + buflen;
|
|
len = buflen;
|
|
prepend(&end, &len, "\0", 1);
|
|
if (buflen < 1)
|
|
goto Elong;
|
|
/* Get '/' right */
|
|
retval = end-1;
|
|
*retval = '/';
|
|
read_seqbegin_or_lock(&rename_lock, &seq);
|
|
while (!IS_ROOT(dentry)) {
|
|
struct dentry *parent = dentry->d_parent;
|
|
int error;
|
|
|
|
prefetch(parent);
|
|
error = prepend_name(&end, &len, &dentry->d_name);
|
|
if (error)
|
|
break;
|
|
|
|
retval = end;
|
|
dentry = parent;
|
|
}
|
|
if (!(seq & 1))
|
|
rcu_read_unlock();
|
|
if (need_seqretry(&rename_lock, seq)) {
|
|
seq = 1;
|
|
goto restart;
|
|
}
|
|
done_seqretry(&rename_lock, seq);
|
|
if (error)
|
|
goto Elong;
|
|
return retval;
|
|
Elong:
|
|
return ERR_PTR(-ENAMETOOLONG);
|
|
}
|
|
|
|
char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
|
|
{
|
|
return __dentry_path(dentry, buf, buflen);
|
|
}
|
|
EXPORT_SYMBOL(dentry_path_raw);
|
|
|
|
char *dentry_path(struct dentry *dentry, char *buf, int buflen)
|
|
{
|
|
char *p = NULL;
|
|
char *retval;
|
|
|
|
if (d_unlinked(dentry)) {
|
|
p = buf + buflen;
|
|
if (prepend(&p, &buflen, "//deleted", 10) != 0)
|
|
goto Elong;
|
|
buflen++;
|
|
}
|
|
retval = __dentry_path(dentry, buf, buflen);
|
|
if (!IS_ERR(retval) && p)
|
|
*p = '/'; /* restore '/' overriden with '\0' */
|
|
return retval;
|
|
Elong:
|
|
return ERR_PTR(-ENAMETOOLONG);
|
|
}
|
|
|
|
/*
|
|
* NOTE! The user-level library version returns a
|
|
* character pointer. The kernel system call just
|
|
* returns the length of the buffer filled (which
|
|
* includes the ending '\0' character), or a negative
|
|
* error value. So libc would do something like
|
|
*
|
|
* char *getcwd(char * buf, size_t size)
|
|
* {
|
|
* int retval;
|
|
*
|
|
* retval = sys_getcwd(buf, size);
|
|
* if (retval >= 0)
|
|
* return buf;
|
|
* errno = -retval;
|
|
* return NULL;
|
|
* }
|
|
*/
|
|
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
|
|
{
|
|
int error;
|
|
struct path pwd, root;
|
|
char *page = (char *) __get_free_page(GFP_USER);
|
|
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
get_fs_root_and_pwd(current->fs, &root, &pwd);
|
|
|
|
error = -ENOENT;
|
|
br_read_lock(&vfsmount_lock);
|
|
if (!d_unlinked(pwd.dentry)) {
|
|
unsigned long len;
|
|
char *cwd = page + PAGE_SIZE;
|
|
int buflen = PAGE_SIZE;
|
|
|
|
prepend(&cwd, &buflen, "\0", 1);
|
|
error = prepend_path(&pwd, &root, &cwd, &buflen);
|
|
br_read_unlock(&vfsmount_lock);
|
|
|
|
if (error < 0)
|
|
goto out;
|
|
|
|
/* Unreachable from current root */
|
|
if (error > 0) {
|
|
error = prepend_unreachable(&cwd, &buflen);
|
|
if (error)
|
|
goto out;
|
|
}
|
|
|
|
error = -ERANGE;
|
|
len = PAGE_SIZE + page - cwd;
|
|
if (len <= size) {
|
|
error = len;
|
|
if (copy_to_user(buf, cwd, len))
|
|
error = -EFAULT;
|
|
}
|
|
} else {
|
|
br_read_unlock(&vfsmount_lock);
|
|
}
|
|
|
|
out:
|
|
path_put(&pwd);
|
|
path_put(&root);
|
|
free_page((unsigned long) page);
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Test whether new_dentry is a subdirectory of old_dentry.
|
|
*
|
|
* Trivially implemented using the dcache structure
|
|
*/
|
|
|
|
/**
|
|
* is_subdir - is new dentry a subdirectory of old_dentry
|
|
* @new_dentry: new dentry
|
|
* @old_dentry: old dentry
|
|
*
|
|
* Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
|
|
* Returns 0 otherwise.
|
|
* Caller must ensure that "new_dentry" is pinned before calling is_subdir()
|
|
*/
|
|
|
|
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
|
|
{
|
|
int result;
|
|
unsigned seq;
|
|
|
|
if (new_dentry == old_dentry)
|
|
return 1;
|
|
|
|
do {
|
|
/* for restarting inner loop in case of seq retry */
|
|
seq = read_seqbegin(&rename_lock);
|
|
/*
|
|
* Need rcu_readlock to protect against the d_parent trashing
|
|
* due to d_move
|
|
*/
|
|
rcu_read_lock();
|
|
if (d_ancestor(old_dentry, new_dentry))
|
|
result = 1;
|
|
else
|
|
result = 0;
|
|
rcu_read_unlock();
|
|
} while (read_seqretry(&rename_lock, seq));
|
|
|
|
return result;
|
|
}
|
|
|
|
static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
|
|
{
|
|
struct dentry *root = data;
|
|
if (dentry != root) {
|
|
if (d_unhashed(dentry) || !dentry->d_inode)
|
|
return D_WALK_SKIP;
|
|
|
|
if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
|
|
dentry->d_flags |= DCACHE_GENOCIDE;
|
|
dentry->d_lockref.count--;
|
|
}
|
|
}
|
|
return D_WALK_CONTINUE;
|
|
}
|
|
|
|
void d_genocide(struct dentry *parent)
|
|
{
|
|
d_walk(parent, parent, d_genocide_kill, NULL);
|
|
}
|
|
|
|
void d_tmpfile(struct dentry *dentry, struct inode *inode)
|
|
{
|
|
inode_dec_link_count(inode);
|
|
BUG_ON(dentry->d_name.name != dentry->d_iname ||
|
|
!hlist_unhashed(&dentry->d_alias) ||
|
|
!d_unlinked(dentry));
|
|
spin_lock(&dentry->d_parent->d_lock);
|
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
|
|
dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
|
|
(unsigned long long)inode->i_ino);
|
|
spin_unlock(&dentry->d_lock);
|
|
spin_unlock(&dentry->d_parent->d_lock);
|
|
d_instantiate(dentry, inode);
|
|
}
|
|
EXPORT_SYMBOL(d_tmpfile);
|
|
|
|
static __initdata unsigned long dhash_entries;
|
|
static int __init set_dhash_entries(char *str)
|
|
{
|
|
if (!str)
|
|
return 0;
|
|
dhash_entries = simple_strtoul(str, &str, 0);
|
|
return 1;
|
|
}
|
|
__setup("dhash_entries=", set_dhash_entries);
|
|
|
|
static void __init dcache_init_early(void)
|
|
{
|
|
unsigned int loop;
|
|
|
|
/* If hashes are distributed across NUMA nodes, defer
|
|
* hash allocation until vmalloc space is available.
|
|
*/
|
|
if (hashdist)
|
|
return;
|
|
|
|
dentry_hashtable =
|
|
alloc_large_system_hash("Dentry cache",
|
|
sizeof(struct hlist_bl_head),
|
|
dhash_entries,
|
|
13,
|
|
HASH_EARLY,
|
|
&d_hash_shift,
|
|
&d_hash_mask,
|
|
0,
|
|
0);
|
|
|
|
for (loop = 0; loop < (1U << d_hash_shift); loop++)
|
|
INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
|
|
}
|
|
|
|
static void __init dcache_init(void)
|
|
{
|
|
unsigned int loop;
|
|
|
|
/*
|
|
* A constructor could be added for stable state like the lists,
|
|
* but it is probably not worth it because of the cache nature
|
|
* of the dcache.
|
|
*/
|
|
dentry_cache = KMEM_CACHE(dentry,
|
|
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
|
|
|
|
/* Hash may have been set up in dcache_init_early */
|
|
if (!hashdist)
|
|
return;
|
|
|
|
dentry_hashtable =
|
|
alloc_large_system_hash("Dentry cache",
|
|
sizeof(struct hlist_bl_head),
|
|
dhash_entries,
|
|
13,
|
|
0,
|
|
&d_hash_shift,
|
|
&d_hash_mask,
|
|
0,
|
|
0);
|
|
|
|
for (loop = 0; loop < (1U << d_hash_shift); loop++)
|
|
INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
|
|
}
|
|
|
|
/* SLAB cache for __getname() consumers */
|
|
struct kmem_cache *names_cachep __read_mostly;
|
|
EXPORT_SYMBOL(names_cachep);
|
|
|
|
EXPORT_SYMBOL(d_genocide);
|
|
|
|
void __init vfs_caches_init_early(void)
|
|
{
|
|
dcache_init_early();
|
|
inode_init_early();
|
|
}
|
|
|
|
void __init vfs_caches_init(unsigned long mempages)
|
|
{
|
|
unsigned long reserve;
|
|
|
|
/* Base hash sizes on available memory, with a reserve equal to
|
|
150% of current kernel size */
|
|
|
|
reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
|
|
mempages -= reserve;
|
|
|
|
names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
|
|
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
|
|
|
|
dcache_init();
|
|
inode_init();
|
|
files_init(mempages);
|
|
mnt_init();
|
|
bdev_cache_init();
|
|
chrdev_init();
|
|
}
|