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btrfs: fix log tree replay failure due to file with 0 links and extents

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commit 0a32e4f002 upstream.

If we log a new inode (not persisted in a past transaction) that has 0
links and extents, then log another inode with an higher inode number, we
end up with failing to replay the log tree with -EINVAL. The steps for
this are:

1) create new file A
2) write some data to file A
3) open an fd on file A
4) unlink file A
5) fsync file A using the previously open fd
6) create file B (has higher inode number than file A)
7) fsync file B
8) power fail before current transaction commits

Now when attempting to mount the fs, the log replay will fail with
-ENOENT at replay_one_extent() when attempting to replay the first
extent of file A. The failure comes when trying to open the inode for
file A in the subvolume tree, since it doesn't exist.

Before commit 5f61b96159 ("btrfs: fix inode lookup error handling
during log replay"), the returned error was -EIO instead of -ENOENT,
since we converted any errors when attempting to read an inode during
log replay to -EIO.

The reason for this is that the log replay procedure fails to ignore
the current inode when we are at the stage LOG_WALK_REPLAY_ALL, our
current inode has 0 links and last inode we processed in the previous
stage has a non 0 link count. In other words, the issue is that at
replay_one_extent() we only update wc->ignore_cur_inode if the current
replay stage is LOG_WALK_REPLAY_INODES.

Fix this by updating wc->ignore_cur_inode whenever we find an inode item
regardless of the current replay stage. This is a simple solution and easy
to backport, but later we can do other alternatives like avoid logging
extents or inode items other than the inode item for inodes with a link
count of 0.

The problem with the wc->ignore_cur_inode logic has been around since
commit f2d72f42d5 ("Btrfs: fix warning when replaying log after fsync
of a tmpfile") but it only became frequent to hit since the more recent
commit 5e85262e54 ("btrfs: fix fsync of files with no hard links not
persisting deletion"), because we stopped skipping inodes with a link
count of 0 when logging, while before the problem would only be triggered
if trying to replay a log tree created with an older kernel which has a
logged inode with 0 links.

A test case for fstests will be submitted soon.

Reported-by: Peter Jung <ptr1337@cachyos.org>
Link: https://lore.kernel.org/linux-btrfs/fce139db-4458-4788-bb97-c29acf6cb1df@cachyos.org/
Reported-by: burneddi <burneddi@protonmail.com>
Link: https://lore.kernel.org/linux-btrfs/lh4W-Lwc0Mbk-QvBhhQyZxf6VbM3E8VtIvU3fPIQgweP_Q1n7wtlUZQc33sYlCKYd-o6rryJQfhHaNAOWWRKxpAXhM8NZPojzsJPyHMf2qY=@protonmail.com/#t
Reported-by: Russell Haley <yumpusamongus@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/598ecc75-eb80-41b3-83c2-f2317fbb9864@gmail.com/
Fixes: f2d72f42d5 ("Btrfs: fix warning when replaying log after fsync of a tmpfile")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Filipe Manana 2025-07-30 19:18:37 +01:00 committed by Greg Kroah-Hartman
parent a754add836
commit 485e1b15c0
1 changed files with 30 additions and 18 deletions
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48
fs/btrfs/tree-log.c
View File

@ -321,8 +321,7 @@ struct walk_control {
/*
* Ignore any items from the inode currently being processed. Needs
* to be set every time we find a BTRFS_INODE_ITEM_KEY and we are in
* the LOG_WALK_REPLAY_INODES stage.
* to be set every time we find a BTRFS_INODE_ITEM_KEY.
*/
bool ignore_cur_inode;
@ -2434,23 +2433,30 @@ static int replay_one_buffer(struct btrfs_root *log, struct extent_buffer *eb,
nritems = btrfs_header_nritems(eb);
for (i = 0; i < nritems; i++) {
struct btrfs_inode_item *inode_item;
btrfs_item_key_to_cpu(eb, &key, i);
/* inode keys are done during the first stage */
if (key.type == BTRFS_INODE_ITEM_KEY &&
wc->stage == LOG_WALK_REPLAY_INODES) {
struct btrfs_inode_item *inode_item;
u32 mode;
inode_item = btrfs_item_ptr(eb, i,
struct btrfs_inode_item);
if (key.type == BTRFS_INODE_ITEM_KEY) {
inode_item = btrfs_item_ptr(eb, i, struct btrfs_inode_item);
/*
* If we have a tmpfile (O_TMPFILE) that got fsync'ed
* and never got linked before the fsync, skip it, as
* replaying it is pointless since it would be deleted
* later. We skip logging tmpfiles, but it's always
* possible we are replaying a log created with a kernel
* that used to log tmpfiles.
* An inode with no links is either:
*
* 1) A tmpfile (O_TMPFILE) that got fsync'ed and never
* got linked before the fsync, skip it, as replaying
* it is pointless since it would be deleted later.
* We skip logging tmpfiles, but it's always possible
* we are replaying a log created with a kernel that
* used to log tmpfiles;
*
* 2) A non-tmpfile which got its last link deleted
* while holding an open fd on it and later got
* fsynced through that fd. We always log the
* parent inodes when inode->last_unlink_trans is
* set to the current transaction, so ignore all the
* inode items for this inode. We will delete the
* inode when processing the parent directory with
* replay_dir_deletes().
*/
if (btrfs_inode_nlink(eb, inode_item) == 0) {
wc->ignore_cur_inode = true;
@ -2458,8 +2464,14 @@ static int replay_one_buffer(struct btrfs_root *log, struct extent_buffer *eb,
} else {
wc->ignore_cur_inode = false;
}
ret = replay_xattr_deletes(wc->trans, root, log,
path, key.objectid);
}
/* Inode keys are done during the first stage. */
if (key.type == BTRFS_INODE_ITEM_KEY &&
wc->stage == LOG_WALK_REPLAY_INODES) {
u32 mode;
ret = replay_xattr_deletes(wc->trans, root, log, path, key.objectid);
if (ret)
break;
mode = btrfs_inode_mode(eb, inode_item);