linux/fs/sysfs/mount.c
Eric Sandeen dc351252b3 sysfs: store sysfs inode nrs in s_ino to avoid readdir oopses
Backport of
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc1/2.6.22-rc1-mm1/broken-out/gregkh-driver-sysfs-allocate-inode-number-using-ida.patch

For regular files in sysfs, sysfs_readdir wants to traverse
sysfs_dirent->s_dentry->d_inode->i_ino to get to the inode number.
But, the dentry can be reclaimed under memory pressure, and there is
no synchronization with readdir.  This patch follows Tejun's scheme of
allocating and storing an inode number in the new s_ino member of a
sysfs_dirent, when dirents are created, and retrieving it from there
for readdir, so that the pointer chain doesn't have to be traversed.

Tejun's upstream patch uses a new-ish "ida" allocator which brings
along some extra complexity; this -stable patch has a brain-dead
incrementing counter which does not guarantee uniqueness, but because
sysfs doesn't hash inodes as iunique expects, uniqueness wasn't
guaranteed today anyway.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2007-06-12 16:08:46 -07:00

120 lines
2.7 KiB
C

/*
* mount.c - operations for initializing and mounting sysfs.
*/
#define DEBUG
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <asm/semaphore.h>
#include "sysfs.h"
/* Random magic number */
#define SYSFS_MAGIC 0x62656572
struct vfsmount *sysfs_mount;
struct super_block * sysfs_sb = NULL;
struct kmem_cache *sysfs_dir_cachep;
static void sysfs_clear_inode(struct inode *inode);
static const struct super_operations sysfs_ops = {
.statfs = simple_statfs,
.drop_inode = sysfs_delete_inode,
.clear_inode = sysfs_clear_inode,
};
static struct sysfs_dirent sysfs_root = {
.s_sibling = LIST_HEAD_INIT(sysfs_root.s_sibling),
.s_children = LIST_HEAD_INIT(sysfs_root.s_children),
.s_element = NULL,
.s_type = SYSFS_ROOT,
.s_iattr = NULL,
.s_ino = 1,
};
static void sysfs_clear_inode(struct inode *inode)
{
kfree(inode->i_private);
}
static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
struct dentry *root;
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = SYSFS_MAGIC;
sb->s_op = &sysfs_ops;
sb->s_time_gran = 1;
sysfs_sb = sb;
inode = sysfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
&sysfs_root);
if (inode) {
inode->i_op = &sysfs_dir_inode_operations;
inode->i_fop = &sysfs_dir_operations;
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
} else {
pr_debug("sysfs: could not get root inode\n");
return -ENOMEM;
}
root = d_alloc_root(inode);
if (!root) {
pr_debug("%s: could not get root dentry!\n",__FUNCTION__);
iput(inode);
return -ENOMEM;
}
root->d_fsdata = &sysfs_root;
sb->s_root = root;
return 0;
}
static int sysfs_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
return get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
}
static struct file_system_type sysfs_fs_type = {
.name = "sysfs",
.get_sb = sysfs_get_sb,
.kill_sb = kill_litter_super,
};
int __init sysfs_init(void)
{
int err = -ENOMEM;
sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
sizeof(struct sysfs_dirent),
0, 0, NULL, NULL);
if (!sysfs_dir_cachep)
goto out;
err = register_filesystem(&sysfs_fs_type);
if (!err) {
sysfs_mount = kern_mount(&sysfs_fs_type);
if (IS_ERR(sysfs_mount)) {
printk(KERN_ERR "sysfs: could not mount!\n");
err = PTR_ERR(sysfs_mount);
sysfs_mount = NULL;
unregister_filesystem(&sysfs_fs_type);
goto out_err;
}
} else
goto out_err;
out:
return err;
out_err:
kmem_cache_destroy(sysfs_dir_cachep);
sysfs_dir_cachep = NULL;
goto out;
}