[PATCH 17/21] Btrfs: fix for incorrect directory entries after fsync log replay

David Sterba
2016-06-03T15:43:25Z

From: Filipe Manana <fdmanana@suse.com>

commit 657ed1aa4898c8304500e0d13f240d5a67e8be5f upstream.

If we move a directory to a new parent and later log that parent and don't
explicitly log the old parent, when we replay the log we can end up with
entries for the moved directory in both the old and new parent directories.
Besides being ilegal to have directories with multiple hard links in linux,
it also resulted in the leaving the inode item with a link count of 1.
A similar issue also happens if we move a regular file - after the log tree
is replayed the file has a link in both the old and new parent directories,
when it should be only at the new directory.

Sample reproducer:

$ mkfs.btrfs -f /dev/sdc
$ mount /dev/sdc /mnt
$ mkdir /mnt/x
$ mkdir /mnt/y
$ touch /mnt/x/foo
$ mkdir /mnt/y/z
$ sync
$ ln /mnt/x/foo /mnt/x/bar
$ mv /mnt/y/z /mnt/x/z
< power fail >
$ mount /dev/sdc /mnt
$ ls -1Ri /mnt
/mnt:
257 x
258 y

/mnt/x:
259 bar
259 foo
260 z

/mnt/x/z:

/mnt/y:
260 z

/mnt/y/z:

$ umount /dev/sdc
$ btrfs check /dev/sdc
Checking filesystem on /dev/sdc
UUID: a67e2c4a-a4b4-4fdc-b015-9d9af1e344be
checking extents
checking free space cache
checking fs roots
root 5 inode 260 errors 2000, link count wrong
unresolved ref dir 257 index 4 namelen 1 name z filetype 2 errors 0
unresolved ref dir 258 index 2 namelen 1 name z filetype 2 errors 0
(...)

Attempting to remove the directory becomes impossible:

$ mount /dev/sdc /mnt
$ rmdir /mnt/y/z
$ ls -lh /mnt/y
ls: cannot access /mnt/y/z: No such file or directory
total 0
d????????? ? ? ? ? ? z
$ rmdir /mnt/x/z
rmdir: failed to remove ‘/mnt/x/z’: Stale file handle
$ ls -lh /mnt/x
ls: cannot access /mnt/x/z: Stale file handle
total 0
-rw-r--r-- 2 root root 0 Apr 6 18:06 bar
-rw-r--r-- 2 root root 0 Apr 6 18:06 foo
d????????? ? ? ? ? ? z

So make sure that on rename we set the last_unlink_trans value for our
inode, even if it's a directory, to the value of the current transaction's
ID and that if the new parent directory is logged that we fallback to a
transaction commit.

A test case for fstests is being submitted as well.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
fs/btrfs/tree-log.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 58ae0a2ce65c..23df70e7f884 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -5277,11 +5277,16 @@ static int btrfs_log_all_parents(struct btrfs_trans_handle *trans,
if (IS_ERR(dir_inode))
continue;

+ if (ctx)
+ ctx->log_new_dentries = false;
ret = btrfs_log_inode(trans, root, dir_inode,
LOG_INODE_ALL, 0, LLONG_MAX, ctx);
if (!ret &&
btrfs_must_commit_transaction(trans, dir_inode))
ret = 1;
+ if (!ret && ctx && ctx->log_new_dentries)
+ ret = log_new_dir_dentries(trans, root,
+ dir_inode, ctx);
iput(dir_inode);
if (ret)
goto out;
@@ -5651,11 +5656,9 @@ void btrfs_record_unlink_dir(struct btrfs_trans_handle *trans,
* into the file. When the file is logged we check it and
* don't log the parents if the file is fully on disk.
*/
- if (S_ISREG(inode->i_mode)) {
- mutex_lock(&BTRFS_I(inode)->log_mutex);
- BTRFS_I(inode)->last_unlink_trans = trans->transid;
- mutex_unlock(&BTRFS_I(inode)->log_mutex);
- }
+ mutex_lock(&BTRFS_I(inode)->log_mutex);
+ BTRFS_I(inode)->last_unlink_trans = trans->transid;
+ mutex_unlock(&BTRFS_I(inode)->log_mutex);

/*
* if this directory was already logged any new
--
2.7.1