WSL2-Linux-Kernel/fs/libfs.c

651 строка
15 KiB
C

/*
* fs/libfs.c
* Library for filesystems writers.
*/
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <asm/uaccess.h>
int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat)
{
struct inode *inode = dentry->d_inode;
generic_fillattr(inode, stat);
stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
return 0;
}
int simple_statfs(struct super_block *sb, struct kstatfs *buf)
{
buf->f_type = sb->s_magic;
buf->f_bsize = PAGE_CACHE_SIZE;
buf->f_namelen = NAME_MAX;
return 0;
}
/*
* Retaining negative dentries for an in-memory filesystem just wastes
* memory and lookup time: arrange for them to be deleted immediately.
*/
static int simple_delete_dentry(struct dentry *dentry)
{
return 1;
}
/*
* Lookup the data. This is trivial - if the dentry didn't already
* exist, we know it is negative. Set d_op to delete negative dentries.
*/
struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
static struct dentry_operations simple_dentry_operations = {
.d_delete = simple_delete_dentry,
};
if (dentry->d_name.len > NAME_MAX)
return ERR_PTR(-ENAMETOOLONG);
dentry->d_op = &simple_dentry_operations;
d_add(dentry, NULL);
return NULL;
}
int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
{
return 0;
}
int dcache_dir_open(struct inode *inode, struct file *file)
{
static struct qstr cursor_name = {.len = 1, .name = "."};
file->private_data = d_alloc(file->f_dentry, &cursor_name);
return file->private_data ? 0 : -ENOMEM;
}
int dcache_dir_close(struct inode *inode, struct file *file)
{
dput(file->private_data);
return 0;
}
loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
{
mutex_lock(&file->f_dentry->d_inode->i_mutex);
switch (origin) {
case 1:
offset += file->f_pos;
case 0:
if (offset >= 0)
break;
default:
mutex_unlock(&file->f_dentry->d_inode->i_mutex);
return -EINVAL;
}
if (offset != file->f_pos) {
file->f_pos = offset;
if (file->f_pos >= 2) {
struct list_head *p;
struct dentry *cursor = file->private_data;
loff_t n = file->f_pos - 2;
spin_lock(&dcache_lock);
list_del(&cursor->d_u.d_child);
p = file->f_dentry->d_subdirs.next;
while (n && p != &file->f_dentry->d_subdirs) {
struct dentry *next;
next = list_entry(p, struct dentry, d_u.d_child);
if (!d_unhashed(next) && next->d_inode)
n--;
p = p->next;
}
list_add_tail(&cursor->d_u.d_child, p);
spin_unlock(&dcache_lock);
}
}
mutex_unlock(&file->f_dentry->d_inode->i_mutex);
return offset;
}
/* Relationship between i_mode and the DT_xxx types */
static inline unsigned char dt_type(struct inode *inode)
{
return (inode->i_mode >> 12) & 15;
}
/*
* Directory is locked and all positive dentries in it are safe, since
* for ramfs-type trees they can't go away without unlink() or rmdir(),
* both impossible due to the lock on directory.
*/
int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_dentry;
struct dentry *cursor = filp->private_data;
struct list_head *p, *q = &cursor->d_u.d_child;
ino_t ino;
int i = filp->f_pos;
switch (i) {
case 0:
ino = dentry->d_inode->i_ino;
if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
break;
filp->f_pos++;
i++;
/* fallthrough */
case 1:
ino = parent_ino(dentry);
if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
break;
filp->f_pos++;
i++;
/* fallthrough */
default:
spin_lock(&dcache_lock);
if (filp->f_pos == 2) {
list_del(q);
list_add(q, &dentry->d_subdirs);
}
for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
struct dentry *next;
next = list_entry(p, struct dentry, d_u.d_child);
if (d_unhashed(next) || !next->d_inode)
continue;
spin_unlock(&dcache_lock);
if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
return 0;
spin_lock(&dcache_lock);
/* next is still alive */
list_del(q);
list_add(q, p);
p = q;
filp->f_pos++;
}
spin_unlock(&dcache_lock);
}
return 0;
}
ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
{
return -EISDIR;
}
struct file_operations simple_dir_operations = {
.open = dcache_dir_open,
.release = dcache_dir_close,
.llseek = dcache_dir_lseek,
.read = generic_read_dir,
.readdir = dcache_readdir,
.fsync = simple_sync_file,
};
struct inode_operations simple_dir_inode_operations = {
.lookup = simple_lookup,
};
/*
* Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
* will never be mountable)
*/
struct super_block *
get_sb_pseudo(struct file_system_type *fs_type, char *name,
struct super_operations *ops, unsigned long magic)
{
struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
static struct super_operations default_ops = {.statfs = simple_statfs};
struct dentry *dentry;
struct inode *root;
struct qstr d_name = {.name = name, .len = strlen(name)};
if (IS_ERR(s))
return s;
s->s_flags = MS_NOUSER;
s->s_maxbytes = ~0ULL;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_magic = magic;
s->s_op = ops ? ops : &default_ops;
s->s_time_gran = 1;
root = new_inode(s);
if (!root)
goto Enomem;
root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
root->i_uid = root->i_gid = 0;
root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
dentry = d_alloc(NULL, &d_name);
if (!dentry) {
iput(root);
goto Enomem;
}
dentry->d_sb = s;
dentry->d_parent = dentry;
d_instantiate(dentry, root);
s->s_root = dentry;
s->s_flags |= MS_ACTIVE;
return s;
Enomem:
up_write(&s->s_umount);
deactivate_super(s);
return ERR_PTR(-ENOMEM);
}
int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{
struct inode *inode = old_dentry->d_inode;
inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
inode->i_nlink++;
atomic_inc(&inode->i_count);
dget(dentry);
d_instantiate(dentry, inode);
return 0;
}
static inline int simple_positive(struct dentry *dentry)
{
return dentry->d_inode && !d_unhashed(dentry);
}
int simple_empty(struct dentry *dentry)
{
struct dentry *child;
int ret = 0;
spin_lock(&dcache_lock);
list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
if (simple_positive(child))
goto out;
ret = 1;
out:
spin_unlock(&dcache_lock);
return ret;
}
int simple_unlink(struct inode *dir, struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
inode->i_nlink--;
dput(dentry);
return 0;
}
int simple_rmdir(struct inode *dir, struct dentry *dentry)
{
if (!simple_empty(dentry))
return -ENOTEMPTY;
dentry->d_inode->i_nlink--;
simple_unlink(dir, dentry);
dir->i_nlink--;
return 0;
}
int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
struct inode *inode = old_dentry->d_inode;
int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
if (!simple_empty(new_dentry))
return -ENOTEMPTY;
if (new_dentry->d_inode) {
simple_unlink(new_dir, new_dentry);
if (they_are_dirs)
old_dir->i_nlink--;
} else if (they_are_dirs) {
old_dir->i_nlink--;
new_dir->i_nlink++;
}
old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
return 0;
}
int simple_readpage(struct file *file, struct page *page)
{
void *kaddr;
if (PageUptodate(page))
goto out;
kaddr = kmap_atomic(page, KM_USER0);
memset(kaddr, 0, PAGE_CACHE_SIZE);
kunmap_atomic(kaddr, KM_USER0);
flush_dcache_page(page);
SetPageUptodate(page);
out:
unlock_page(page);
return 0;
}
int simple_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
if (!PageUptodate(page)) {
if (to - from != PAGE_CACHE_SIZE) {
void *kaddr = kmap_atomic(page, KM_USER0);
memset(kaddr, 0, from);
memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
}
SetPageUptodate(page);
}
return 0;
}
int simple_commit_write(struct file *file, struct page *page,
unsigned offset, unsigned to)
{
struct inode *inode = page->mapping->host;
loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
/*
* No need to use i_size_read() here, the i_size
* cannot change under us because we hold the i_mutex.
*/
if (pos > inode->i_size)
i_size_write(inode, pos);
set_page_dirty(page);
return 0;
}
int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
{
static struct super_operations s_ops = {.statfs = simple_statfs};
struct inode *inode;
struct dentry *root;
struct dentry *dentry;
int i;
s->s_blocksize = PAGE_CACHE_SIZE;
s->s_blocksize_bits = PAGE_CACHE_SHIFT;
s->s_magic = magic;
s->s_op = &s_ops;
s->s_time_gran = 1;
inode = new_inode(s);
if (!inode)
return -ENOMEM;
inode->i_mode = S_IFDIR | 0755;
inode->i_uid = inode->i_gid = 0;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
root = d_alloc_root(inode);
if (!root) {
iput(inode);
return -ENOMEM;
}
for (i = 0; !files->name || files->name[0]; i++, files++) {
if (!files->name)
continue;
dentry = d_alloc_name(root, files->name);
if (!dentry)
goto out;
inode = new_inode(s);
if (!inode)
goto out;
inode->i_mode = S_IFREG | files->mode;
inode->i_uid = inode->i_gid = 0;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_fop = files->ops;
inode->i_ino = i;
d_add(dentry, inode);
}
s->s_root = root;
return 0;
out:
d_genocide(root);
dput(root);
return -ENOMEM;
}
static DEFINE_SPINLOCK(pin_fs_lock);
int simple_pin_fs(char *name, struct vfsmount **mount, int *count)
{
struct vfsmount *mnt = NULL;
spin_lock(&pin_fs_lock);
if (unlikely(!*mount)) {
spin_unlock(&pin_fs_lock);
mnt = do_kern_mount(name, 0, name, NULL);
if (IS_ERR(mnt))
return PTR_ERR(mnt);
spin_lock(&pin_fs_lock);
if (!*mount)
*mount = mnt;
}
mntget(*mount);
++*count;
spin_unlock(&pin_fs_lock);
mntput(mnt);
return 0;
}
void simple_release_fs(struct vfsmount **mount, int *count)
{
struct vfsmount *mnt;
spin_lock(&pin_fs_lock);
mnt = *mount;
if (!--*count)
*mount = NULL;
spin_unlock(&pin_fs_lock);
mntput(mnt);
}
ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
const void *from, size_t available)
{
loff_t pos = *ppos;
if (pos < 0)
return -EINVAL;
if (pos >= available)
return 0;
if (count > available - pos)
count = available - pos;
if (copy_to_user(to, from + pos, count))
return -EFAULT;
*ppos = pos + count;
return count;
}
/*
* Transaction based IO.
* The file expects a single write which triggers the transaction, and then
* possibly a read which collects the result - which is stored in a
* file-local buffer.
*/
char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
{
struct simple_transaction_argresp *ar;
static DEFINE_SPINLOCK(simple_transaction_lock);
if (size > SIMPLE_TRANSACTION_LIMIT - 1)
return ERR_PTR(-EFBIG);
ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
if (!ar)
return ERR_PTR(-ENOMEM);
spin_lock(&simple_transaction_lock);
/* only one write allowed per open */
if (file->private_data) {
spin_unlock(&simple_transaction_lock);
free_page((unsigned long)ar);
return ERR_PTR(-EBUSY);
}
file->private_data = ar;
spin_unlock(&simple_transaction_lock);
if (copy_from_user(ar->data, buf, size))
return ERR_PTR(-EFAULT);
return ar->data;
}
ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
{
struct simple_transaction_argresp *ar = file->private_data;
if (!ar)
return 0;
return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
}
int simple_transaction_release(struct inode *inode, struct file *file)
{
free_page((unsigned long)file->private_data);
return 0;
}
/* Simple attribute files */
struct simple_attr {
u64 (*get)(void *);
void (*set)(void *, u64);
char get_buf[24]; /* enough to store a u64 and "\n\0" */
char set_buf[24];
void *data;
const char *fmt; /* format for read operation */
struct semaphore sem; /* protects access to these buffers */
};
/* simple_attr_open is called by an actual attribute open file operation
* to set the attribute specific access operations. */
int simple_attr_open(struct inode *inode, struct file *file,
u64 (*get)(void *), void (*set)(void *, u64),
const char *fmt)
{
struct simple_attr *attr;
attr = kmalloc(sizeof(*attr), GFP_KERNEL);
if (!attr)
return -ENOMEM;
attr->get = get;
attr->set = set;
attr->data = inode->u.generic_ip;
attr->fmt = fmt;
init_MUTEX(&attr->sem);
file->private_data = attr;
return nonseekable_open(inode, file);
}
int simple_attr_close(struct inode *inode, struct file *file)
{
kfree(file->private_data);
return 0;
}
/* read from the buffer that is filled with the get function */
ssize_t simple_attr_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
struct simple_attr *attr;
size_t size;
ssize_t ret;
attr = file->private_data;
if (!attr->get)
return -EACCES;
down(&attr->sem);
if (*ppos) /* continued read */
size = strlen(attr->get_buf);
else /* first read */
size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
attr->fmt,
(unsigned long long)attr->get(attr->data));
ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
up(&attr->sem);
return ret;
}
/* interpret the buffer as a number to call the set function with */
ssize_t simple_attr_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos)
{
struct simple_attr *attr;
u64 val;
size_t size;
ssize_t ret;
attr = file->private_data;
if (!attr->set)
return -EACCES;
down(&attr->sem);
ret = -EFAULT;
size = min(sizeof(attr->set_buf) - 1, len);
if (copy_from_user(attr->set_buf, buf, size))
goto out;
ret = len; /* claim we got the whole input */
attr->set_buf[size] = '\0';
val = simple_strtol(attr->set_buf, NULL, 0);
attr->set(attr->data, val);
out:
up(&attr->sem);
return ret;
}
EXPORT_SYMBOL(dcache_dir_close);
EXPORT_SYMBOL(dcache_dir_lseek);
EXPORT_SYMBOL(dcache_dir_open);
EXPORT_SYMBOL(dcache_readdir);
EXPORT_SYMBOL(generic_read_dir);
EXPORT_SYMBOL(get_sb_pseudo);
EXPORT_SYMBOL(simple_commit_write);
EXPORT_SYMBOL(simple_dir_inode_operations);
EXPORT_SYMBOL(simple_dir_operations);
EXPORT_SYMBOL(simple_empty);
EXPORT_SYMBOL(d_alloc_name);
EXPORT_SYMBOL(simple_fill_super);
EXPORT_SYMBOL(simple_getattr);
EXPORT_SYMBOL(simple_link);
EXPORT_SYMBOL(simple_lookup);
EXPORT_SYMBOL(simple_pin_fs);
EXPORT_SYMBOL(simple_prepare_write);
EXPORT_SYMBOL(simple_readpage);
EXPORT_SYMBOL(simple_release_fs);
EXPORT_SYMBOL(simple_rename);
EXPORT_SYMBOL(simple_rmdir);
EXPORT_SYMBOL(simple_statfs);
EXPORT_SYMBOL(simple_sync_file);
EXPORT_SYMBOL(simple_unlink);
EXPORT_SYMBOL(simple_read_from_buffer);
EXPORT_SYMBOL(simple_transaction_get);
EXPORT_SYMBOL(simple_transaction_read);
EXPORT_SYMBOL(simple_transaction_release);
EXPORT_SYMBOL_GPL(simple_attr_open);
EXPORT_SYMBOL_GPL(simple_attr_close);
EXPORT_SYMBOL_GPL(simple_attr_read);
EXPORT_SYMBOL_GPL(simple_attr_write);