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WSL2-Linux-Kernel
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WSL2-Linux-Kernel/fs/locks.c

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54 KiB
C
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/*
* linux/fs/locks.c
*
* Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
* Doug Evans (dje@spiff.uucp), August 07, 1992
*
* Deadlock detection added.
* FIXME: one thing isn't handled yet:
* - mandatory locks (requires lots of changes elsewhere)
* Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
*
* Miscellaneous edits, and a total rewrite of posix_lock_file() code.
* Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
*
* Converted file_lock_table to a linked list from an array, which eliminates
* the limits on how many active file locks are open.
* Chad Page (pageone@netcom.com), November 27, 1994
*
* Removed dependency on file descriptors. dup()'ed file descriptors now
* get the same locks as the original file descriptors, and a close() on
* any file descriptor removes ALL the locks on the file for the current
* process. Since locks still depend on the process id, locks are inherited
* after an exec() but not after a fork(). This agrees with POSIX, and both
* BSD and SVR4 practice.
* Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
*
* Scrapped free list which is redundant now that we allocate locks
* dynamically with kmalloc()/kfree().
* Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
*
* Implemented two lock personalities - FL_FLOCK and FL_POSIX.
*
* FL_POSIX locks are created with calls to fcntl() and lockf() through the
* fcntl() system call. They have the semantics described above.
*
* FL_FLOCK locks are created with calls to flock(), through the flock()
* system call, which is new. Old C libraries implement flock() via fcntl()
* and will continue to use the old, broken implementation.
*
* FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
* with a file pointer (filp). As a result they can be shared by a parent
* process and its children after a fork(). They are removed when the last
* file descriptor referring to the file pointer is closed (unless explicitly
* unlocked).
*
* FL_FLOCK locks never deadlock, an existing lock is always removed before
* upgrading from shared to exclusive (or vice versa). When this happens
* any processes blocked by the current lock are woken up and allowed to
* run before the new lock is applied.
* Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
*
* Removed some race conditions in flock_lock_file(), marked other possible
* races. Just grep for FIXME to see them.
* Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
*
* Addressed Dmitry's concerns. Deadlock checking no longer recursive.
* Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
* once we've checked for blocking and deadlocking.
* Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
*
* Initial implementation of mandatory locks. SunOS turned out to be
* a rotten model, so I implemented the "obvious" semantics.
* See 'Documentation/mandatory.txt' for details.
* Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
*
* Don't allow mandatory locks on mmap()'ed files. Added simple functions to
* check if a file has mandatory locks, used by mmap(), open() and creat() to
* see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
* Manual, Section 2.
* Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
*
* Tidied up block list handling. Added '/proc/locks' interface.
* Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
*
* Fixed deadlock condition for pathological code that mixes calls to
* flock() and fcntl().
* Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
*
* Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
* for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
* guarantee sensible behaviour in the case where file system modules might
* be compiled with different options than the kernel itself.
* Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
*
* Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
* (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
* Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
*
* Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
* locks. Changed process synchronisation to avoid dereferencing locks that
* have already been freed.
* Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
*
* Made the block list a circular list to minimise searching in the list.
* Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
*
* Made mandatory locking a mount option. Default is not to allow mandatory
* locking.
* Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
*
* Some adaptations for NFS support.
* Olaf Kirch (okir@monad.swb.de), Dec 1996,
*
* Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
* Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
*
* Use slab allocator instead of kmalloc/kfree.
* Use generic list implementation from <linux/list.h>.
* Sped up posix_locks_deadlock by only considering blocked locks.
* Matthew Wilcox <willy@debian.org>, March, 2000.
*
* Leases and LOCK_MAND
* Matthew Wilcox <willy@debian.org>, June, 2000.
* Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
*/
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/syscalls.h>
#include <linux/time.h>
#include <asm/semaphore.h>
#include <asm/uaccess.h>
#define IS_POSIX(fl) (fl->fl_flags & FL_POSIX)
#define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK)
#define IS_LEASE(fl) (fl->fl_flags & FL_LEASE)
int leases_enable = 1;
int lease_break_time = 45;
#define for_each_lock(inode, lockp) \
for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
LIST_HEAD(file_lock_list);
EXPORT_SYMBOL(file_lock_list);
static LIST_HEAD(blocked_list);
static kmem_cache_t *filelock_cache;
/* Allocate an empty lock structure. */
static struct file_lock *locks_alloc_lock(void)
{
return kmem_cache_alloc(filelock_cache, SLAB_KERNEL);
}
/* Free a lock which is not in use. */
static inline void locks_free_lock(struct file_lock *fl)
{
if (fl == NULL) {
BUG();
return;
}
if (waitqueue_active(&fl->fl_wait))
panic("Attempting to free lock with active wait queue");
if (!list_empty(&fl->fl_block))
panic("Attempting to free lock with active block list");
if (!list_empty(&fl->fl_link))
panic("Attempting to free lock on active lock list");
if (fl->fl_ops) {
if (fl->fl_ops->fl_release_private)
fl->fl_ops->fl_release_private(fl);
fl->fl_ops = NULL;
}
if (fl->fl_lmops) {
if (fl->fl_lmops->fl_release_private)
fl->fl_lmops->fl_release_private(fl);
fl->fl_lmops = NULL;
}
kmem_cache_free(filelock_cache, fl);
}
void locks_init_lock(struct file_lock *fl)
{
INIT_LIST_HEAD(&fl->fl_link);
INIT_LIST_HEAD(&fl->fl_block);
init_waitqueue_head(&fl->fl_wait);
fl->fl_next = NULL;
fl->fl_fasync = NULL;
fl->fl_owner = NULL;
fl->fl_pid = 0;
fl->fl_file = NULL;
fl->fl_flags = 0;
fl->fl_type = 0;
fl->fl_start = fl->fl_end = 0;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
}
EXPORT_SYMBOL(locks_init_lock);
/*
* Initialises the fields of the file lock which are invariant for
* free file_locks.
*/
static void init_once(void *foo, kmem_cache_t *cache, unsigned long flags)
{
struct file_lock *lock = (struct file_lock *) foo;
if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) !=
SLAB_CTOR_CONSTRUCTOR)
return;
locks_init_lock(lock);
}
/*
* Initialize a new lock from an existing file_lock structure.
*/
void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
{
new->fl_owner = fl->fl_owner;
new->fl_pid = fl->fl_pid;
new->fl_file = fl->fl_file;
new->fl_flags = fl->fl_flags;
new->fl_type = fl->fl_type;
new->fl_start = fl->fl_start;
new->fl_end = fl->fl_end;
new->fl_ops = fl->fl_ops;
new->fl_lmops = fl->fl_lmops;
if (fl->fl_ops && fl->fl_ops->fl_copy_lock)
fl->fl_ops->fl_copy_lock(new, fl);
if (fl->fl_lmops && fl->fl_lmops->fl_copy_lock)
fl->fl_lmops->fl_copy_lock(new, fl);
}
EXPORT_SYMBOL(locks_copy_lock);
static inline int flock_translate_cmd(int cmd) {
if (cmd & LOCK_MAND)
return cmd & (LOCK_MAND | LOCK_RW);
switch (cmd) {
case LOCK_SH:
return F_RDLCK;
case LOCK_EX:
return F_WRLCK;
case LOCK_UN:
return F_UNLCK;
}
return -EINVAL;
}
/* Fill in a file_lock structure with an appropriate FLOCK lock. */
static int flock_make_lock(struct file *filp, struct file_lock **lock,
unsigned int cmd)
{
struct file_lock *fl;
int type = flock_translate_cmd(cmd);
if (type < 0)
return type;
fl = locks_alloc_lock();
if (fl == NULL)
return -ENOMEM;
fl->fl_file = filp;
fl->fl_pid = current->tgid;
fl->fl_flags = FL_FLOCK;
fl->fl_type = type;
fl->fl_end = OFFSET_MAX;
*lock = fl;
return 0;
}
static int assign_type(struct file_lock *fl, int type)
{
switch (type) {
case F_RDLCK:
case F_WRLCK:
case F_UNLCK:
fl->fl_type = type;
break;
default:
return -EINVAL;
}
return 0;
}
/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
* style lock.
*/
static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock *l)
{
off_t start, end;
switch (l->l_whence) {
case 0: /*SEEK_SET*/
start = 0;
break;
case 1: /*SEEK_CUR*/
start = filp->f_pos;
break;
case 2: /*SEEK_END*/
start = i_size_read(filp->f_dentry->d_inode);
break;
default:
return -EINVAL;
}
/* POSIX-1996 leaves the case l->l_len < 0 undefined;
POSIX-2001 defines it. */
start += l->l_start;
end = start + l->l_len - 1;
if (l->l_len < 0) {
end = start - 1;
start += l->l_len;
}
if (start < 0)
return -EINVAL;
if (l->l_len > 0 && end < 0)
return -EOVERFLOW;
fl->fl_start = start; /* we record the absolute position */
fl->fl_end = end;
if (l->l_len == 0)
fl->fl_end = OFFSET_MAX;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
return assign_type(fl, l->l_type);
}
#if BITS_PER_LONG == 32
static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock64 *l)
{
loff_t start;
switch (l->l_whence) {
case 0: /*SEEK_SET*/
start = 0;
break;
case 1: /*SEEK_CUR*/
start = filp->f_pos;
break;
case 2: /*SEEK_END*/
start = i_size_read(filp->f_dentry->d_inode);
break;
default:
return -EINVAL;
}
if (((start += l->l_start) < 0) || (l->l_len < 0))
return -EINVAL;
fl->fl_end = start + l->l_len - 1;
if (l->l_len > 0 && fl->fl_end < 0)
return -EOVERFLOW;
fl->fl_start = start; /* we record the absolute position */
if (l->l_len == 0)
fl->fl_end = OFFSET_MAX;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
switch (l->l_type) {
case F_RDLCK:
case F_WRLCK:
case F_UNLCK:
fl->fl_type = l->l_type;
break;
default:
return -EINVAL;
}
return (0);
}
#endif
/* default lease lock manager operations */
static void lease_break_callback(struct file_lock *fl)
{
kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
}
static void lease_release_private_callback(struct file_lock *fl)
{
if (!fl->fl_file)
return;
f_delown(fl->fl_file);
fl->fl_file->f_owner.signum = 0;
}
int lease_mylease_callback(struct file_lock *fl, struct file_lock *try)
{
return fl->fl_file == try->fl_file;
}
struct lock_manager_operations lease_manager_ops = {
.fl_break = lease_break_callback,
.fl_release_private = lease_release_private_callback,
.fl_mylease = lease_mylease_callback,
.fl_change = lease_modify,
};
/*
* Initialize a lease, use the default lock manager operations
*/
static int lease_init(struct file *filp, int type, struct file_lock *fl)
{
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_LEASE;
if (assign_type(fl, type) != 0) {
locks_free_lock(fl);
return -EINVAL;
}
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
fl->fl_ops = NULL;
fl->fl_lmops = &lease_manager_ops;
return 0;
}
/* Allocate a file_lock initialised to this type of lease */
static int lease_alloc(struct file *filp, int type, struct file_lock **flp)
{
struct file_lock *fl = locks_alloc_lock();
int error;
if (fl == NULL)
return -ENOMEM;
error = lease_init(filp, type, fl);
if (error)
return error;
*flp = fl;
return 0;
}
/* Check if two locks overlap each other.
*/
static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
{
return ((fl1->fl_end >= fl2->fl_start) &&
(fl2->fl_end >= fl1->fl_start));
}
/*
* Check whether two locks have the same owner.
*/
static inline int
posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
{
if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner)
return fl2->fl_lmops == fl1->fl_lmops &&
fl1->fl_lmops->fl_compare_owner(fl1, fl2);
return fl1->fl_owner == fl2->fl_owner;
}
/* Remove waiter from blocker's block list.
* When blocker ends up pointing to itself then the list is empty.
*/
static inline void __locks_delete_block(struct file_lock *waiter)
{
list_del_init(&waiter->fl_block);
list_del_init(&waiter->fl_link);
waiter->fl_next = NULL;
}
/*
*/
static void locks_delete_block(struct file_lock *waiter)
{
lock_kernel();
__locks_delete_block(waiter);
unlock_kernel();
}
/* Insert waiter into blocker's block list.
* We use a circular list so that processes can be easily woken up in
* the order they blocked. The documentation doesn't require this but
* it seems like the reasonable thing to do.
*/
static void locks_insert_block(struct file_lock *blocker,
struct file_lock *waiter)
{
if (!list_empty(&waiter->fl_block)) {
printk(KERN_ERR "locks_insert_block: removing duplicated lock "
"(pid=%d %Ld-%Ld type=%d)\n", waiter->fl_pid,
waiter->fl_start, waiter->fl_end, waiter->fl_type);
__locks_delete_block(waiter);
}
list_add_tail(&waiter->fl_block, &blocker->fl_block);
waiter->fl_next = blocker;
if (IS_POSIX(blocker))
list_add(&waiter->fl_link, &blocked_list);
}
/* Wake up processes blocked waiting for blocker.
* If told to wait then schedule the processes until the block list
* is empty, otherwise empty the block list ourselves.
*/
static void locks_wake_up_blocks(struct file_lock *blocker)
{
while (!list_empty(&blocker->fl_block)) {
struct file_lock *waiter = list_entry(blocker->fl_block.next,
struct file_lock, fl_block);
__locks_delete_block(waiter);
if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
waiter->fl_lmops->fl_notify(waiter);
else
wake_up(&waiter->fl_wait);
}
}
/* Insert file lock fl into an inode's lock list at the position indicated
* by pos. At the same time add the lock to the global file lock list.
*/
static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
{
list_add(&fl->fl_link, &file_lock_list);
/* insert into file's list */
fl->fl_next = *pos;
*pos = fl;
if (fl->fl_ops && fl->fl_ops->fl_insert)
fl->fl_ops->fl_insert(fl);
}
/*
* Delete a lock and then free it.
* Wake up processes that are blocked waiting for this lock,
* notify the FS that the lock has been cleared and
* finally free the lock.
*/
static void locks_delete_lock(struct file_lock **thisfl_p)
{
struct file_lock *fl = *thisfl_p;
*thisfl_p = fl->fl_next;
fl->fl_next = NULL;
list_del_init(&fl->fl_link);
fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
if (fl->fl_fasync != NULL) {
printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
fl->fl_fasync = NULL;
}
if (fl->fl_ops && fl->fl_ops->fl_remove)
fl->fl_ops->fl_remove(fl);
locks_wake_up_blocks(fl);
locks_free_lock(fl);
}
/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
* checks for shared/exclusive status of overlapping locks.
*/
static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
if (sys_fl->fl_type == F_WRLCK)
return 1;
if (caller_fl->fl_type == F_WRLCK)
return 1;
return 0;
}
/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
* checking before calling the locks_conflict().
*/
static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
/* POSIX locks owned by the same process do not conflict with
* each other.
*/
if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
return (0);
/* Check whether they overlap */
if (!locks_overlap(caller_fl, sys_fl))
return 0;
return (locks_conflict(caller_fl, sys_fl));
}
/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
* checking before calling the locks_conflict().
*/
static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
/* FLOCK locks referring to the same filp do not conflict with
* each other.
*/
if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
return (0);
if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
return 0;
return (locks_conflict(caller_fl, sys_fl));
}
static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
{
int result = 0;
DECLARE_WAITQUEUE(wait, current);
__set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(fl_wait, &wait);
if (timeout == 0)
schedule();
else
result = schedule_timeout(timeout);
if (signal_pending(current))
result = -ERESTARTSYS;
remove_wait_queue(fl_wait, &wait);
__set_current_state(TASK_RUNNING);
return result;
}
static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
{
int result;
locks_insert_block(blocker, waiter);
result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
__locks_delete_block(waiter);
return result;
}
struct file_lock *
posix_test_lock(struct file *filp, struct file_lock *fl)
{
struct file_lock *cfl;
lock_kernel();
for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
if (!IS_POSIX(cfl))
continue;
if (posix_locks_conflict(cfl, fl))
break;
}
unlock_kernel();
return (cfl);
}
EXPORT_SYMBOL(posix_test_lock);
/* This function tests for deadlock condition before putting a process to
* sleep. The detection scheme is no longer recursive. Recursive was neat,
* but dangerous - we risked stack corruption if the lock data was bad, or
* if the recursion was too deep for any other reason.
*
* We rely on the fact that a task can only be on one lock's wait queue
* at a time. When we find blocked_task on a wait queue we can re-search
* with blocked_task equal to that queue's owner, until either blocked_task
* isn't found, or blocked_task is found on a queue owned by my_task.
*
* Note: the above assumption may not be true when handling lock requests
* from a broken NFS client. But broken NFS clients have a lot more to
* worry about than proper deadlock detection anyway... --okir
*/
int posix_locks_deadlock(struct file_lock *caller_fl,
struct file_lock *block_fl)
{
struct list_head *tmp;
next_task:
if (posix_same_owner(caller_fl, block_fl))
return 1;
list_for_each(tmp, &blocked_list) {
struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
if (posix_same_owner(fl, block_fl)) {
fl = fl->fl_next;
block_fl = fl;
goto next_task;
}
}
return 0;
}
EXPORT_SYMBOL(posix_locks_deadlock);
/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
* at the head of the list, but that's secret knowledge known only to
* flock_lock_file and posix_lock_file.
*/
static int flock_lock_file(struct file *filp, struct file_lock *new_fl)
{
struct file_lock **before;
struct inode * inode = filp->f_dentry->d_inode;
int error = 0;
int found = 0;
lock_kernel();
for_each_lock(inode, before) {
struct file_lock *fl = *before;
if (IS_POSIX(fl))
break;
if (IS_LEASE(fl))
continue;
if (filp != fl->fl_file)
continue;
if (new_fl->fl_type == fl->fl_type)
goto out;
found = 1;
locks_delete_lock(before);
break;
}
unlock_kernel();
if (new_fl->fl_type == F_UNLCK)
return 0;
/*
* If a higher-priority process was blocked on the old file lock,
* give it the opportunity to lock the file.
*/
if (found)
cond_resched();
lock_kernel();
for_each_lock(inode, before) {
struct file_lock *fl = *before;
if (IS_POSIX(fl))
break;
if (IS_LEASE(fl))
continue;
if (!flock_locks_conflict(new_fl, fl))
continue;
error = -EAGAIN;
if (new_fl->fl_flags & FL_SLEEP) {
locks_insert_block(fl, new_fl);
}
goto out;
}
locks_insert_lock(&inode->i_flock, new_fl);
error = 0;
out:
unlock_kernel();
return error;
}
EXPORT_SYMBOL(posix_lock_file);
static int __posix_lock_file(struct inode *inode, struct file_lock *request)
{
struct file_lock *fl;
struct file_lock *new_fl, *new_fl2;
struct file_lock *left = NULL;
struct file_lock *right = NULL;
struct file_lock **before;
int error, added = 0;
/*
* We may need two file_lock structures for this operation,
* so we get them in advance to avoid races.
*/
new_fl = locks_alloc_lock();
new_fl2 = locks_alloc_lock();
lock_kernel();
if (request->fl_type != F_UNLCK) {
for_each_lock(inode, before) {
struct file_lock *fl = *before;
if (!IS_POSIX(fl))
continue;
if (!posix_locks_conflict(request, fl))
continue;
error = -EAGAIN;
if (!(request->fl_flags & FL_SLEEP))
goto out;
error = -EDEADLK;
if (posix_locks_deadlock(request, fl))
goto out;
error = -EAGAIN;
locks_insert_block(fl, request);
goto out;
}
}
/* If we're just looking for a conflict, we're done. */
error = 0;
if (request->fl_flags & FL_ACCESS)
goto out;
error = -ENOLCK; /* "no luck" */
if (!(new_fl && new_fl2))
goto out;
/*
* We've allocated the new locks in advance, so there are no
* errors possible (and no blocking operations) from here on.
*
* Find the first old lock with the same owner as the new lock.
*/
before = &inode->i_flock;
/* First skip locks owned by other processes. */
while ((fl = *before) && (!IS_POSIX(fl) ||
!posix_same_owner(request, fl))) {
before = &fl->fl_next;
}
/* Process locks with this owner. */
while ((fl = *before) && posix_same_owner(request, fl)) {
/* Detect adjacent or overlapping regions (if same lock type)
*/
if (request->fl_type == fl->fl_type) {
if (fl->fl_end < request->fl_start - 1)
goto next_lock;
/* If the next lock in the list has entirely bigger
* addresses than the new one, insert the lock here.
*/
if (fl->fl_start > request->fl_end + 1)
break;
/* If we come here, the new and old lock are of the
* same type and adjacent or overlapping. Make one
* lock yielding from the lower start address of both
* locks to the higher end address.
*/
if (fl->fl_start > request->fl_start)
fl->fl_start = request->fl_start;
else
request->fl_start = fl->fl_start;
if (fl->fl_end < request->fl_end)
fl->fl_end = request->fl_end;
else
request->fl_end = fl->fl_end;
if (added) {
locks_delete_lock(before);
continue;
}
request = fl;
added = 1;
}
else {
/* Processing for different lock types is a bit
* more complex.
*/
if (fl->fl_end < request->fl_start)
goto next_lock;
if (fl->fl_start > request->fl_end)
break;
if (request->fl_type == F_UNLCK)
added = 1;
if (fl->fl_start < request->fl_start)
left = fl;
/* If the next lock in the list has a higher end
* address than the new one, insert the new one here.
*/
if (fl->fl_end > request->fl_end) {
right = fl;
break;
}
if (fl->fl_start >= request->fl_start) {
/* The new lock completely replaces an old
* one (This may happen several times).
*/
if (added) {
locks_delete_lock(before);
continue;
}
/* Replace the old lock with the new one.
* Wake up anybody waiting for the old one,
* as the change in lock type might satisfy
* their needs.
*/
locks_wake_up_blocks(fl);
fl->fl_start = request->fl_start;
fl->fl_end = request->fl_end;
fl->fl_type = request->fl_type;
fl->fl_u = request->fl_u;
request = fl;
added = 1;
}
}
/* Go on to next lock.
*/
next_lock:
before = &fl->fl_next;
}
error = 0;
if (!added) {
if (request->fl_type == F_UNLCK)
goto out;
locks_copy_lock(new_fl, request);
locks_insert_lock(before, new_fl);
new_fl = NULL;
}
if (right) {
if (left == right) {
/* The new lock breaks the old one in two pieces,
* so we have to use the second new lock.
*/
left = new_fl2;
new_fl2 = NULL;
locks_copy_lock(left, right);
locks_insert_lock(before, left);
}
right->fl_start = request->fl_end + 1;
locks_wake_up_blocks(right);
}
if (left) {
left->fl_end = request->fl_start - 1;
locks_wake_up_blocks(left);
}
out:
unlock_kernel();
/*
* Free any unused locks.
*/
if (new_fl)
locks_free_lock(new_fl);
if (new_fl2)
locks_free_lock(new_fl2);
return error;
}
/**
* posix_lock_file - Apply a POSIX-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
*
* Add a POSIX style lock to a file.
* We merge adjacent & overlapping locks whenever possible.
* POSIX locks are sorted by owner task, then by starting address
*/
int posix_lock_file(struct file *filp, struct file_lock *fl)
{
return __posix_lock_file(filp->f_dentry->d_inode, fl);
}
/**
* posix_lock_file_wait - Apply a POSIX-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
*
* Add a POSIX style lock to a file.
* We merge adjacent & overlapping locks whenever possible.
* POSIX locks are sorted by owner task, then by starting address
*/
int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
{
int error;
might_sleep ();
for (;;) {
error = __posix_lock_file(filp->f_dentry->d_inode, fl);
if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
break;
error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
if (!error)
continue;
locks_delete_block(fl);
break;
}
return error;
}
EXPORT_SYMBOL(posix_lock_file_wait);
/**
* locks_mandatory_locked - Check for an active lock
* @inode: the file to check
*
* Searches the inode's list of locks to find any POSIX locks which conflict.
* This function is called from locks_verify_locked() only.
*/
int locks_mandatory_locked(struct inode *inode)
{
fl_owner_t owner = current->files;
struct file_lock *fl;
/*
* Search the lock list for this inode for any POSIX locks.
*/
lock_kernel();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (!IS_POSIX(fl))
continue;
if (fl->fl_owner != owner)
break;
}
unlock_kernel();
return fl ? -EAGAIN : 0;
}
/**
* locks_mandatory_area - Check for a conflicting lock
* @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
* for shared
* @inode: the file to check
* @filp: how the file was opened (if it was)
* @offset: start of area to check
* @count: length of area to check
*
* Searches the inode's list of locks to find any POSIX locks which conflict.
* This function is called from rw_verify_area() and
* locks_verify_truncate().
*/
int locks_mandatory_area(int read_write, struct inode *inode,
struct file *filp, loff_t offset,
size_t count)
{
struct file_lock fl;
int error;
locks_init_lock(&fl);
fl.fl_owner = current->files;
fl.fl_pid = current->tgid;
fl.fl_file = filp;
fl.fl_flags = FL_POSIX | FL_ACCESS;
if (filp && !(filp->f_flags & O_NONBLOCK))
fl.fl_flags |= FL_SLEEP;
fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
fl.fl_start = offset;
fl.fl_end = offset + count - 1;
for (;;) {
error = __posix_lock_file(inode, &fl);
if (error != -EAGAIN)
break;
if (!(fl.fl_flags & FL_SLEEP))
break;
error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
if (!error) {
/*
* If we've been sleeping someone might have
* changed the permissions behind our back.
*/
if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
continue;
}
locks_delete_block(&fl);
break;
}
return error;
}
EXPORT_SYMBOL(locks_mandatory_area);
/* We already had a lease on this file; just change its type */
int lease_modify(struct file_lock **before, int arg)
{
struct file_lock *fl = *before;
int error = assign_type(fl, arg);
if (error)
return error;
locks_wake_up_blocks(fl);
if (arg == F_UNLCK)
locks_delete_lock(before);
return 0;
}
EXPORT_SYMBOL(lease_modify);
static void time_out_leases(struct inode *inode)
{
struct file_lock **before;
struct file_lock *fl;
before = &inode->i_flock;
while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) {
if ((fl->fl_break_time == 0)
|| time_before(jiffies, fl->fl_break_time)) {
before = &fl->fl_next;
continue;
}
printk(KERN_INFO "lease broken - owner pid = %d\n", fl->fl_pid);
lease_modify(before, fl->fl_type & ~F_INPROGRESS);
if (fl == *before) /* lease_modify may have freed fl */
before = &fl->fl_next;
}
}
/**
* __break_lease - revoke all outstanding leases on file
* @inode: the inode of the file to return
* @mode: the open mode (read or write)
*
* break_lease (inlined for speed) has checked there already
* is a lease on this file. Leases are broken on a call to open()
* or truncate(). This function can sleep unless you
* specified %O_NONBLOCK to your open().
*/
int __break_lease(struct inode *inode, unsigned int mode)
{
int error = 0, future;
struct file_lock *new_fl, *flock;
struct file_lock *fl;
int alloc_err;
unsigned long break_time;
int i_have_this_lease = 0;
alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK,
&new_fl);
lock_kernel();
time_out_leases(inode);
flock = inode->i_flock;
if ((flock == NULL) || !IS_LEASE(flock))
goto out;
for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
if (fl->fl_owner == current->files)
i_have_this_lease = 1;
if (mode & FMODE_WRITE) {
/* If we want write access, we have to revoke any lease. */
future = F_UNLCK | F_INPROGRESS;
} else if (flock->fl_type & F_INPROGRESS) {
/* If the lease is already being broken, we just leave it */
future = flock->fl_type;
} else if (flock->fl_type & F_WRLCK) {
/* Downgrade the exclusive lease to a read-only lease. */
future = F_RDLCK | F_INPROGRESS;
} else {
/* the existing lease was read-only, so we can read too. */
goto out;
}
if (alloc_err && !i_have_this_lease && ((mode & O_NONBLOCK) == 0)) {
error = alloc_err;
goto out;
}
break_time = 0;
if (lease_break_time > 0) {
break_time = jiffies + lease_break_time * HZ;
if (break_time == 0)
break_time++; /* so that 0 means no break time */
}
for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
if (fl->fl_type != future) {
fl->fl_type = future;
fl->fl_break_time = break_time;
/* lease must have lmops break callback */
fl->fl_lmops->fl_break(fl);
}
}
if (i_have_this_lease || (mode & O_NONBLOCK)) {
error = -EWOULDBLOCK;
goto out;
}
restart:
break_time = flock->fl_break_time;
if (break_time != 0) {
break_time -= jiffies;
if (break_time == 0)
break_time++;
}
error = locks_block_on_timeout(flock, new_fl, break_time);
if (error >= 0) {
if (error == 0)
time_out_leases(inode);
/* Wait for the next lease that has not been broken yet */
for (flock = inode->i_flock; flock && IS_LEASE(flock);
flock = flock->fl_next) {
if (flock->fl_type & F_INPROGRESS)
goto restart;
}
error = 0;
}
out:
unlock_kernel();
if (!alloc_err)
locks_free_lock(new_fl);
return error;
}
EXPORT_SYMBOL(__break_lease);
/**
* lease_get_mtime
* @inode: the inode
* @time: pointer to a timespec which will contain the last modified time
*
* This is to force NFS clients to flush their caches for files with
* exclusive leases. The justification is that if someone has an
* exclusive lease, then they could be modifiying it.
*/
void lease_get_mtime(struct inode *inode, struct timespec *time)
{
struct file_lock *flock = inode->i_flock;
if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK))
*time = current_fs_time(inode->i_sb);
else
*time = inode->i_mtime;
}
EXPORT_SYMBOL(lease_get_mtime);
/**
* fcntl_getlease - Enquire what lease is currently active
* @filp: the file
*
* The value returned by this function will be one of
* (if no lease break is pending):
*
* %F_RDLCK to indicate a shared lease is held.
*
* %F_WRLCK to indicate an exclusive lease is held.
*
* %F_UNLCK to indicate no lease is held.
*
* (if a lease break is pending):
*
* %F_RDLCK to indicate an exclusive lease needs to be
* changed to a shared lease (or removed).
*
* %F_UNLCK to indicate the lease needs to be removed.
*
* XXX: sfr & willy disagree over whether F_INPROGRESS
* should be returned to userspace.
*/
int fcntl_getlease(struct file *filp)
{
struct file_lock *fl;
int type = F_UNLCK;
lock_kernel();
time_out_leases(filp->f_dentry->d_inode);
for (fl = filp->f_dentry->d_inode->i_flock; fl && IS_LEASE(fl);
fl = fl->fl_next) {
if (fl->fl_file == filp) {
type = fl->fl_type & ~F_INPROGRESS;
break;
}
}
unlock_kernel();
return type;
}
/**
* __setlease - sets a lease on an open file
* @filp: file pointer
* @arg: type of lease to obtain
* @flp: input - file_lock to use, output - file_lock inserted
*
* The (input) flp->fl_lmops->fl_break function is required
* by break_lease().
*
* Called with kernel lock held.
*/
int __setlease(struct file *filp, long arg, struct file_lock **flp)
{
struct file_lock *fl, **before, **my_before = NULL, *lease = *flp;
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
int error, rdlease_count = 0, wrlease_count = 0;
time_out_leases(inode);
error = -EINVAL;
if (!flp || !(*flp) || !(*flp)->fl_lmops || !(*flp)->fl_lmops->fl_break)
goto out;
error = -EAGAIN;
if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
goto out;
if ((arg == F_WRLCK)
&& ((atomic_read(&dentry->d_count) > 1)
|| (atomic_read(&inode->i_count) > 1)))
goto out;
/*
* At this point, we know that if there is an exclusive
* lease on this file, then we hold it on this filp
* (otherwise our open of this file would have blocked).
* And if we are trying to acquire an exclusive lease,
* then the file is not open by anyone (including us)
* except for this filp.
*/
for (before = &inode->i_flock;
((fl = *before) != NULL) && IS_LEASE(fl);
before = &fl->fl_next) {
if (lease->fl_lmops->fl_mylease(fl, lease))
my_before = before;
else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
/*
* Someone is in the process of opening this
* file for writing so we may not take an
* exclusive lease on it.
*/
wrlease_count++;
else
rdlease_count++;
}
if ((arg == F_RDLCK && (wrlease_count > 0)) ||
(arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
goto out;
if (my_before != NULL) {
error = lease->fl_lmops->fl_change(my_before, arg);
goto out;
}
error = 0;
if (arg == F_UNLCK)
goto out;
error = -EINVAL;
if (!leases_enable)
goto out;
error = lease_alloc(filp, arg, &fl);
if (error)
goto out;
locks_copy_lock(fl, lease);
locks_insert_lock(before, fl);
*flp = fl;
out:
return error;
}
/**
* setlease - sets a lease on an open file
* @filp: file pointer
* @arg: type of lease to obtain
* @lease: file_lock to use
*
* Call this to establish a lease on the file.
* The fl_lmops fl_break function is required by break_lease
*/
int setlease(struct file *filp, long arg, struct file_lock **lease)
{
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
int error;
if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
return -EACCES;
if (!S_ISREG(inode->i_mode))
return -EINVAL;
error = security_file_lock(filp, arg);
if (error)
return error;
lock_kernel();
error = __setlease(filp, arg, lease);
unlock_kernel();
return error;
}
EXPORT_SYMBOL(setlease);
/**
* fcntl_setlease - sets a lease on an open file
* @fd: open file descriptor
* @filp: file pointer
* @arg: type of lease to obtain
*
* Call this fcntl to establish a lease on the file.
* Note that you also need to call %F_SETSIG to
* receive a signal when the lease is broken.
*/
int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
{
struct file_lock fl, *flp = &fl;
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
int error;
if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
return -EACCES;
if (!S_ISREG(inode->i_mode))
return -EINVAL;
error = security_file_lock(filp, arg);
if (error)
return error;
locks_init_lock(&fl);
error = lease_init(filp, arg, &fl);
if (error)
return error;
lock_kernel();
error = __setlease(filp, arg, &flp);
if (error)
goto out_unlock;
error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
if (error < 0) {
/* remove lease just inserted by __setlease */
flp->fl_type = F_UNLCK | F_INPROGRESS;
flp->fl_break_time = jiffies- 10;
time_out_leases(inode);
goto out_unlock;
}
error = f_setown(filp, current->pid, 0);
out_unlock:
unlock_kernel();
return error;
}
/**
* flock_lock_file_wait - Apply a FLOCK-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
*
* Add a FLOCK style lock to a file.
*/
int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
{
int error;
might_sleep();
for (;;) {
error = flock_lock_file(filp, fl);
if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
break;
error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
if (!error)
continue;
locks_delete_block(fl);
break;
}
return error;
}
EXPORT_SYMBOL(flock_lock_file_wait);
/**
* sys_flock: - flock() system call.
* @fd: the file descriptor to lock.
* @cmd: the type of lock to apply.
*
* Apply a %FL_FLOCK style lock to an open file descriptor.
* The @cmd can be one of
*
* %LOCK_SH -- a shared lock.
*
* %LOCK_EX -- an exclusive lock.
*
* %LOCK_UN -- remove an existing lock.
*
* %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
*
* %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
* processes read and write access respectively.
*/
asmlinkage long sys_flock(unsigned int fd, unsigned int cmd)
{
struct file *filp;
struct file_lock *lock;
int can_sleep, unlock;
int error;
error = -EBADF;
filp = fget(fd);
if (!filp)
goto out;
can_sleep = !(cmd & LOCK_NB);
cmd &= ~LOCK_NB;
unlock = (cmd == LOCK_UN);
if (!unlock && !(cmd & LOCK_MAND) && !(filp->f_mode & 3))
goto out_putf;
error = flock_make_lock(filp, &lock, cmd);
if (error)
goto out_putf;
if (can_sleep)
lock->fl_flags |= FL_SLEEP;
error = security_file_lock(filp, cmd);
if (error)
goto out_free;
if (filp->f_op && filp->f_op->flock)
error = filp->f_op->flock(filp,
(can_sleep) ? F_SETLKW : F_SETLK,
lock);
else
error = flock_lock_file_wait(filp, lock);
out_free:
if (list_empty(&lock->fl_link)) {
locks_free_lock(lock);
}
out_putf:
fput(filp);
out:
return error;
}
/* Report the first existing lock that would conflict with l.
* This implements the F_GETLK command of fcntl().
*/
int fcntl_getlk(struct file *filp, struct flock __user *l)
{
struct file_lock *fl, file_lock;
struct flock flock;
int error;
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
error = -EINVAL;
if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
goto out;
error = flock_to_posix_lock(filp, &file_lock, &flock);
if (error)
goto out;
if (filp->f_op && filp->f_op->lock) {
error = filp->f_op->lock(filp, F_GETLK, &file_lock);
if (error < 0)
goto out;
else
fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
} else {
fl = posix_test_lock(filp, &file_lock);
}
flock.l_type = F_UNLCK;
if (fl != NULL) {
flock.l_pid = fl->fl_pid;
#if BITS_PER_LONG == 32
/*
* Make sure we can represent the posix lock via
* legacy 32bit flock.
*/
error = -EOVERFLOW;
if (fl->fl_start > OFFT_OFFSET_MAX)
goto out;
if ((fl->fl_end != OFFSET_MAX)
&& (fl->fl_end > OFFT_OFFSET_MAX))
goto out;
#endif
flock.l_start = fl->fl_start;
flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
fl->fl_end - fl->fl_start + 1;
flock.l_whence = 0;
flock.l_type = fl->fl_type;
}
error = -EFAULT;
if (!copy_to_user(l, &flock, sizeof(flock)))
error = 0;
out:
return error;
}
/* Apply the lock described by l to an open file descriptor.
* This implements both the F_SETLK and F_SETLKW commands of fcntl().
*/
int fcntl_setlk(struct file *filp, unsigned int cmd, struct flock __user *l)
{
struct file_lock *file_lock = locks_alloc_lock();
struct flock flock;
struct inode *inode;
int error;
if (file_lock == NULL)
return -ENOLCK;
/*
* This might block, so we do it before checking the inode.
*/
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
inode = filp->f_dentry->d_inode;
/* Don't allow mandatory locks on files that may be memory mapped
* and shared.
*/
if (IS_MANDLOCK(inode) &&
(inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
mapping_writably_mapped(filp->f_mapping)) {
error = -EAGAIN;
goto out;
}
error = flock_to_posix_lock(filp, file_lock, &flock);
if (error)
goto out;
if (cmd == F_SETLKW) {
file_lock->fl_flags |= FL_SLEEP;
}
error = -EBADF;
switch (flock.l_type) {
case F_RDLCK:
if (!(filp->f_mode & FMODE_READ))
goto out;
break;
case F_WRLCK:
if (!(filp->f_mode & FMODE_WRITE))
goto out;
break;
case F_UNLCK:
break;
default:
error = -EINVAL;
goto out;
}
error = security_file_lock(filp, file_lock->fl_type);
if (error)
goto out;
if (filp->f_op && filp->f_op->lock != NULL) {
error = filp->f_op->lock(filp, cmd, file_lock);
goto out;
}
for (;;) {
error = __posix_lock_file(inode, file_lock);
if ((error != -EAGAIN) || (cmd == F_SETLK))
break;
error = wait_event_interruptible(file_lock->fl_wait,
!file_lock->fl_next);
if (!error)
continue;
locks_delete_block(file_lock);
break;
}
out:
locks_free_lock(file_lock);
return error;
}
#if BITS_PER_LONG == 32
/* Report the first existing lock that would conflict with l.
* This implements the F_GETLK command of fcntl().
*/
int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
{
struct file_lock *fl, file_lock;
struct flock64 flock;
int error;
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
error = -EINVAL;
if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
goto out;
error = flock64_to_posix_lock(filp, &file_lock, &flock);
if (error)
goto out;
if (filp->f_op && filp->f_op->lock) {
error = filp->f_op->lock(filp, F_GETLK, &file_lock);
if (error < 0)
goto out;
else
fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
} else {
fl = posix_test_lock(filp, &file_lock);
}
flock.l_type = F_UNLCK;
if (fl != NULL) {
flock.l_pid = fl->fl_pid;
flock.l_start = fl->fl_start;
flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
fl->fl_end - fl->fl_start + 1;
flock.l_whence = 0;
flock.l_type = fl->fl_type;
}
error = -EFAULT;
if (!copy_to_user(l, &flock, sizeof(flock)))
error = 0;
out:
return error;
}
/* Apply the lock described by l to an open file descriptor.
* This implements both the F_SETLK and F_SETLKW commands of fcntl().
*/
int fcntl_setlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l)
{
struct file_lock *file_lock = locks_alloc_lock();
struct flock64 flock;
struct inode *inode;
int error;
if (file_lock == NULL)
return -ENOLCK;
/*
* This might block, so we do it before checking the inode.
*/
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
inode = filp->f_dentry->d_inode;
/* Don't allow mandatory locks on files that may be memory mapped
* and shared.
*/
if (IS_MANDLOCK(inode) &&
(inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
mapping_writably_mapped(filp->f_mapping)) {
error = -EAGAIN;
goto out;
}
error = flock64_to_posix_lock(filp, file_lock, &flock);
if (error)
goto out;
if (cmd == F_SETLKW64) {
file_lock->fl_flags |= FL_SLEEP;
}
error = -EBADF;
switch (flock.l_type) {
case F_RDLCK:
if (!(filp->f_mode & FMODE_READ))
goto out;
break;
case F_WRLCK:
if (!(filp->f_mode & FMODE_WRITE))
goto out;
break;
case F_UNLCK:
break;
default:
error = -EINVAL;
goto out;
}
error = security_file_lock(filp, file_lock->fl_type);
if (error)
goto out;
if (filp->f_op && filp->f_op->lock != NULL) {
error = filp->f_op->lock(filp, cmd, file_lock);
goto out;
}
for (;;) {
error = __posix_lock_file(inode, file_lock);
if ((error != -EAGAIN) || (cmd == F_SETLK64))
break;
error = wait_event_interruptible(file_lock->fl_wait,
!file_lock->fl_next);
if (!error)
continue;
locks_delete_block(file_lock);
break;
}
out:
locks_free_lock(file_lock);
return error;
}
#endif /* BITS_PER_LONG == 32 */
/*
* This function is called when the file is being removed
* from the task's fd array. POSIX locks belonging to this task
* are deleted at this time.
*/
void locks_remove_posix(struct file *filp, fl_owner_t owner)
{
struct file_lock lock, **before;
/*
* If there are no locks held on this file, we don't need to call
* posix_lock_file(). Another process could be setting a lock on this
* file at the same time, but we wouldn't remove that lock anyway.
*/
before = &filp->f_dentry->d_inode->i_flock;
if (*before == NULL)
return;
lock.fl_type = F_UNLCK;
lock.fl_flags = FL_POSIX;
lock.fl_start = 0;
lock.fl_end = OFFSET_MAX;
lock.fl_owner = owner;
lock.fl_pid = current->tgid;
lock.fl_file = filp;
lock.fl_ops = NULL;
lock.fl_lmops = NULL;
if (filp->f_op && filp->f_op->lock != NULL) {
filp->f_op->lock(filp, F_SETLK, &lock);
goto out;
}
/* Can't use posix_lock_file here; we need to remove it no matter
* which pid we have.
*/
lock_kernel();
while (*before != NULL) {
struct file_lock *fl = *before;
if (IS_POSIX(fl) && posix_same_owner(fl, &lock)) {
locks_delete_lock(before);
continue;
}
before = &fl->fl_next;
}
unlock_kernel();
out:
if (lock.fl_ops && lock.fl_ops->fl_release_private)
lock.fl_ops->fl_release_private(&lock);
}
EXPORT_SYMBOL(locks_remove_posix);
/*
* This function is called on the last close of an open file.
*/
void locks_remove_flock(struct file *filp)
{
struct inode * inode = filp->f_dentry->d_inode;
struct file_lock *fl;
struct file_lock **before;
if (!inode->i_flock)
return;
if (filp->f_op && filp->f_op->flock) {
struct file_lock fl = {
.fl_pid = current->tgid,
.fl_file = filp,
.fl_flags = FL_FLOCK,
.fl_type = F_UNLCK,
.fl_end = OFFSET_MAX,
};
filp->f_op->flock(filp, F_SETLKW, &fl);
}
lock_kernel();
before = &inode->i_flock;
while ((fl = *before) != NULL) {
if (fl->fl_file == filp) {
/*
* We might have a POSIX lock that was created at the same time
* the filp was closed for the last time. Just remove that too,
* regardless of ownership, since nobody can own it.
*/
if (IS_FLOCK(fl) || IS_POSIX(fl)) {
locks_delete_lock(before);
continue;
}
if (IS_LEASE(fl)) {
lease_modify(before, F_UNLCK);
continue;
}
/* What? */
BUG();
}
before = &fl->fl_next;
}
unlock_kernel();
}
/**
* posix_block_lock - blocks waiting for a file lock
* @blocker: the lock which is blocking
* @waiter: the lock which conflicts and has to wait
*
* lockd needs to block waiting for locks.
*/
void
posix_block_lock(struct file_lock *blocker, struct file_lock *waiter)
{
locks_insert_block(blocker, waiter);
}
EXPORT_SYMBOL(posix_block_lock);
/**
* posix_unblock_lock - stop waiting for a file lock
* @filp: how the file was opened
* @waiter: the lock which was waiting
*
* lockd needs to block waiting for locks.
*/
void
posix_unblock_lock(struct file *filp, struct file_lock *waiter)
{
/*
* A remote machine may cancel the lock request after it's been
* granted locally. If that happens, we need to delete the lock.
*/
lock_kernel();
if (waiter->fl_next) {
__locks_delete_block(waiter);
unlock_kernel();
} else {
unlock_kernel();
waiter->fl_type = F_UNLCK;
posix_lock_file(filp, waiter);
}
}
EXPORT_SYMBOL(posix_unblock_lock);
static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
{
struct inode *inode = NULL;
if (fl->fl_file != NULL)
inode = fl->fl_file->f_dentry->d_inode;
out += sprintf(out, "%d:%s ", id, pfx);
if (IS_POSIX(fl)) {
out += sprintf(out, "%6s %s ",
(fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
(inode == NULL) ? "*NOINODE*" :
(IS_MANDLOCK(inode) &&
(inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ?
"MANDATORY" : "ADVISORY ");
} else if (IS_FLOCK(fl)) {
if (fl->fl_type & LOCK_MAND) {
out += sprintf(out, "FLOCK MSNFS ");
} else {
out += sprintf(out, "FLOCK ADVISORY ");
}
} else if (IS_LEASE(fl)) {
out += sprintf(out, "LEASE ");
if (fl->fl_type & F_INPROGRESS)
out += sprintf(out, "BREAKING ");
else if (fl->fl_file)
out += sprintf(out, "ACTIVE ");
else
out += sprintf(out, "BREAKER ");
} else {
out += sprintf(out, "UNKNOWN UNKNOWN ");
}
if (fl->fl_type & LOCK_MAND) {
out += sprintf(out, "%s ",
(fl->fl_type & LOCK_READ)
? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ "
: (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
} else {
out += sprintf(out, "%s ",
(fl->fl_type & F_INPROGRESS)
? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
: (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
}
if (inode) {
#ifdef WE_CAN_BREAK_LSLK_NOW
out += sprintf(out, "%d %s:%ld ", fl->fl_pid,
inode->i_sb->s_id, inode->i_ino);
#else
/* userspace relies on this representation of dev_t ;-( */
out += sprintf(out, "%d %02x:%02x:%ld ", fl->fl_pid,
MAJOR(inode->i_sb->s_dev),
MINOR(inode->i_sb->s_dev), inode->i_ino);
#endif
} else {
out += sprintf(out, "%d <none>:0 ", fl->fl_pid);
}
if (IS_POSIX(fl)) {
if (fl->fl_end == OFFSET_MAX)
out += sprintf(out, "%Ld EOF\n", fl->fl_start);
else
out += sprintf(out, "%Ld %Ld\n", fl->fl_start,
fl->fl_end);
} else {
out += sprintf(out, "0 EOF\n");
}
}
static void move_lock_status(char **p, off_t* pos, off_t offset)
{
int len;
len = strlen(*p);
if(*pos >= offset) {
/* the complete line is valid */
*p += len;
*pos += len;
return;
}
if(*pos+len > offset) {
/* use the second part of the line */
int i = offset-*pos;
memmove(*p,*p+i,len-i);
*p += len-i;
*pos += len;
return;
}
/* discard the complete line */
*pos += len;
}
/**
* get_locks_status - reports lock usage in /proc/locks
* @buffer: address in userspace to write into
* @start: ?
* @offset: how far we are through the buffer
* @length: how much to read
*/
int get_locks_status(char *buffer, char **start, off_t offset, int length)
{
struct list_head *tmp;
char *q = buffer;
off_t pos = 0;
int i = 0;
lock_kernel();
list_for_each(tmp, &file_lock_list) {
struct list_head *btmp;
struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
lock_get_status(q, fl, ++i, "");
move_lock_status(&q, &pos, offset);
if(pos >= offset+length)
goto done;
list_for_each(btmp, &fl->fl_block) {
struct file_lock *bfl = list_entry(btmp,
struct file_lock, fl_block);
lock_get_status(q, bfl, i, " ->");
move_lock_status(&q, &pos, offset);
if(pos >= offset+length)
goto done;
}
}
done:
unlock_kernel();
*start = buffer;
if(q-buffer < length)
return (q-buffer);
return length;
}
/**
* lock_may_read - checks that the region is free of locks
* @inode: the inode that is being read
* @start: the first byte to read
* @len: the number of bytes to read
*
* Emulates Windows locking requirements. Whole-file
* mandatory locks (share modes) can prohibit a read and
* byte-range POSIX locks can prohibit a read if they overlap.
*
* N.B. this function is only ever called
* from knfsd and ownership of locks is never checked.
*/
int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
{
struct file_lock *fl;
int result = 1;
lock_kernel();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if (fl->fl_type == F_RDLCK)
continue;
if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
continue;
} else if (IS_FLOCK(fl)) {
if (!(fl->fl_type & LOCK_MAND))
continue;
if (fl->fl_type & LOCK_READ)
continue;
} else
continue;
result = 0;
break;
}
unlock_kernel();
return result;
}
EXPORT_SYMBOL(lock_may_read);
/**
* lock_may_write - checks that the region is free of locks
* @inode: the inode that is being written
* @start: the first byte to write
* @len: the number of bytes to write
*
* Emulates Windows locking requirements. Whole-file
* mandatory locks (share modes) can prohibit a write and
* byte-range POSIX locks can prohibit a write if they overlap.
*
* N.B. this function is only ever called
* from knfsd and ownership of locks is never checked.
*/
int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
{
struct file_lock *fl;
int result = 1;
lock_kernel();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
continue;
} else if (IS_FLOCK(fl)) {
if (!(fl->fl_type & LOCK_MAND))
continue;
if (fl->fl_type & LOCK_WRITE)
continue;
} else
continue;
result = 0;
break;
}
unlock_kernel();
return result;
}
EXPORT_SYMBOL(lock_may_write);
static inline void __steal_locks(struct file *file, fl_owner_t from)
{
struct inode *inode = file->f_dentry->d_inode;
struct file_lock *fl = inode->i_flock;
while (fl) {
if (fl->fl_file == file && fl->fl_owner == from)
fl->fl_owner = current->files;
fl = fl->fl_next;
}
}
/* When getting ready for executing a binary, we make sure that current
* has a files_struct on its own. Before dropping the old files_struct,
* we take over ownership of all locks for all file descriptors we own.
* Note that we may accidentally steal a lock for a file that a sibling
* has created since the unshare_files() call.
*/
void steal_locks(fl_owner_t from)
{
struct files_struct *files = current->files;
int i, j;
if (from == files)
return;
lock_kernel();
j = 0;
for (;;) {
unsigned long set;
i = j * __NFDBITS;
if (i >= files->max_fdset || i >= files->max_fds)
break;
set = files->open_fds->fds_bits[j++];
while (set) {
if (set & 1) {
struct file *file = files->fd[i];
if (file)
__steal_locks(file, from);
}
i++;
set >>= 1;
}
}
unlock_kernel();
}
EXPORT_SYMBOL(steal_locks);
static int __init filelock_init(void)
{
filelock_cache = kmem_cache_create("file_lock_cache",
sizeof(struct file_lock), 0, SLAB_PANIC,
init_once, NULL);
return 0;
}
core_initcall(filelock_init);
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