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vfs: prevent remount read-only if pending removes

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If there are any inodes on the super block that have been unlinked
(i_nlink == 0) but have not yet been deleted then prevent the
remounting the super block read-only.

Reported-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Miklos Szeredi 2011-11-21 12:11:33 +01:00 • committed by Al Viro
commit 8e8b87964b
4 changed files with 7 additions and 29 deletions
Download patch file Download diff file Expand all files Collapse all files

23
fs/file_table.c
View file

@ -474,29 +474,6 @@ void file_sb_list_del(struct file *file)
#endif #endif
int fs_may_remount_ro(struct super_block *sb)
{
struct file *file;
/* Check that no files are currently opened for writing. */
lg_global_lock(files_lglock);
do_file_list_for_each_entry(sb, file) {
struct inode *inode = file->f_path.dentry->d_inode;
/* File with pending delete? */
if (inode->i_nlink == 0)
goto too_bad;
/* Writeable file? */
if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
goto too_bad;
} while_file_list_for_each_entry;
lg_global_unlock(files_lglock);
return 1; /* Tis' cool bro. */
too_bad:
lg_global_unlock(files_lglock);
return 0;
}
/** /**
* mark_files_ro - mark all files read-only * mark_files_ro - mark all files read-only
* @sb: superblock in question * @sb: superblock in question

7
fs/namespace.c
View file

@ -449,6 +449,10 @@ int sb_prepare_remount_readonly(struct super_block *sb)
struct mount *mnt; struct mount *mnt;
int err = 0; int err = 0;
/* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
if (atomic_long_read(&sb->s_remove_count))
return -EBUSY;
br_write_lock(vfsmount_lock); br_write_lock(vfsmount_lock);
list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
@ -460,6 +464,9 @@ int sb_prepare_remount_readonly(struct super_block *sb)
} }
} }
} }
if (!err && atomic_long_read(&sb->s_remove_count))
err = -EBUSY;
if (!err) { if (!err) {
sb->s_readonly_remount = 1; sb->s_readonly_remount = 1;
smp_wmb(); smp_wmb();

4
fs/super.c
View file

@ -729,10 +729,6 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
retval = sb_prepare_remount_readonly(sb); retval = sb_prepare_remount_readonly(sb);
if (retval) if (retval)
return retval; return retval;
retval = -EBUSY;
if (!fs_may_remount_ro(sb))
goto cancel_readonly;
} }
} }

2
include/linux/fs.h
View file

@ -2150,8 +2150,6 @@ extern const struct file_operations read_pipefifo_fops;
extern const struct file_operations write_pipefifo_fops; extern const struct file_operations write_pipefifo_fops;
extern const struct file_operations rdwr_pipefifo_fops; extern const struct file_operations rdwr_pipefifo_fops;
extern int fs_may_remount_ro(struct super_block *);
#ifdef CONFIG_BLOCK #ifdef CONFIG_BLOCK
/* /*
* return READ, READA, or WRITE * return READ, READA, or WRITE