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/*
* fs/libfs.c
* Library for filesystems writers.
*/
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
int simple_statfs(struct super_block *sb, struct statfs *buf)
{
buf->f_type = sb->s_magic;
buf->f_bsize = PAGE_CACHE_SIZE;
buf->f_namelen = NAME_MAX;
return 0;
}
/*
* Lookup the data. This is trivial - if the dentry didn't already
* exist, we know it is negative.
*/
struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry)
{
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)
{
down(&file->f_dentry->d_inode->i_sem);
switch (origin) {
case 1:
offset += file->f_pos;
case 0:
if (offset >= 0)
break;
default:
up(&file->f_dentry->d_inode->i_sem);
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);
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_child);
if (!list_empty(&next->d_hash) && next->d_inode)
n--;
p = p->next;
}
list_del(&cursor->d_child);
list_add_tail(&cursor->d_child, p);
spin_unlock(&dcache_lock);
}
}
up(&file->f_dentry->d_inode->i_sem);
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_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_child);
if (list_empty(&next->d_hash) || !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 *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,
};
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;
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);
}
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