[PATCH 6.12 246/567] btrfs: dont log conflicting inode if its a dir moved in the current transaction

Greg Kroah-Hartman
2026-01-06T17:29:34Z

From: Filipe Manana <fdmanana@suse.com>

commit 266273eaf4d99475f1ae57f687b3e42bc71ec6f0 upstream.

We can't log a conflicting inode if it's a directory and it was moved
from one parent directory to another parent directory in the current
transaction, as this can result an attempt to have a directory with
two hard links during log replay, one for the old parent directory and
another for the new parent directory.

The following scenario triggers that issue:

1) We have directories "dir1" and "dir2" created in a past transaction.
Directory "dir1" has inode A as its parent directory;

2) We move "dir1" to some other directory;

3) We create a file with the name "dir1" in directory inode A;

4) We fsync the new file. This results in logging the inode of the new file
and the inode for the directory "dir1" that was previously moved in the
current transaction. So the log tree has the INODE_REF item for the
new location of "dir1";

5) We move the new file to some other directory. This results in updating
the log tree to included the new INODE_REF for the new location of the
file and removes the INODE_REF for the old location. This happens
during the rename when we call btrfs_log_new_name();

6) We fsync the file, and that persists the log tree changes done in the
previous step (btrfs_log_new_name() only updates the log tree in
memory);

7) We have a power failure;

8) Next time the fs is mounted, log replay happens and when processing
the inode for directory "dir1" we find a new INODE_REF and add that
link, but we don't remove the old link of the inode since we have
not logged the old parent directory of the directory inode "dir1".

As a result after log replay finishes when we trigger writeback of the
subvolume tree's extent buffers, the tree check will detect that we have
a directory a hard link count of 2 and we get a mount failure.
The errors and stack traces reported in dmesg/syslog are like this:

[ 3845.729764] BTRFS info (device dm-0): start tree-log replay
[ 3845.730304] page: refcount:3 mapcount:0 mapping:000000005c8a3027 index:0x1d00 pfn:0x11510c
[ 3845.731236] memcg:ffff9264c02f4e00
[ 3845.731751] aops:btree_aops [btrfs] ino:1
[ 3845.732300] flags: 0x17fffc00000400a(uptodate|private|writeback|node=0|zone=2|lastcpupid=0x1ffff)
[ 3845.733346] raw: 017fffc00000400a 0000000000000000 dead000000000122 ffff9264d978aea8
[ 3845.734265] raw: 0000000000001d00 ffff92650e6d4738 00000003ffffffff ffff9264c02f4e00
[ 3845.735305] page dumped because: eb page dump
[ 3845.735981] BTRFS critical (device dm-0): corrupt leaf: root=5 block=30408704 slot=6 ino=257, invalid nlink: has 2 expect no more than 1 for dir
[ 3845.737786] BTRFS info (device dm-0): leaf 30408704 gen 10 total ptrs 17 free space 14881 owner 5
[ 3845.737789] BTRFS info (device dm-0): refs 4 lock_owner 0 current 30701
[ 3845.737792] item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160
[ 3845.737794] inode generation 3 transid 9 size 16 nbytes 16384
[ 3845.737795] block group 0 mode 40755 links 1 uid 0 gid 0
[ 3845.737797] rdev 0 sequence 2 flags 0x0
[ 3845.737798] atime 1764259517.0
[ 3845.737800] ctime 1764259517.572889464
[ 3845.737801] mtime 1764259517.572889464
[ 3845.737802] otime 1764259517.0
[ 3845.737803] item 1 key (256 INODE_REF 256) itemoff 16111 itemsize 12
[ 3845.737805] index 0 name_len 2
[ 3845.737807] item 2 key (256 DIR_ITEM 2363071922) itemoff 16077 itemsize 34
[ 3845.737808] location key (257 1 0) type 2
[ 3845.737810] transid 9 data_len 0 name_len 4
[ 3845.737811] item 3 key (256 DIR_ITEM 2676584006) itemoff 16043 itemsize 34
[ 3845.737813] location key (258 1 0) type 2
[ 3845.737814] transid 9 data_len 0 name_len 4
[ 3845.737815] item 4 key (256 DIR_INDEX 2) itemoff 16009 itemsize 34
[ 3845.737816] location key (257 1 0) type 2
[ 3845.737818] transid 9 data_len 0 name_len 4
[ 3845.737819] item 5 key (256 DIR_INDEX 3) itemoff 15975 itemsize 34
[ 3845.737820] location key (258 1 0) type 2
[ 3845.737821] transid 9 data_len 0 name_len 4
[ 3845.737822] item 6 key (257 INODE_ITEM 0) itemoff 15815 itemsize 160
[ 3845.737824] inode generation 9 transid 10 size 6 nbytes 0
[ 3845.737825] block group 0 mode 40755 links 2 uid 0 gid 0
[ 3845.737826] rdev 0 sequence 1 flags 0x0
[ 3845.737827] atime 1764259517.572889464
[ 3845.737828] ctime 1764259517.572889464
[ 3845.737830] mtime 1764259517.572889464
[ 3845.737831] otime 1764259517.572889464
[ 3845.737832] item 7 key (257 INODE_REF 256) itemoff 15801 itemsize 14
[ 3845.737833] index 2 name_len 4
[ 3845.737834] item 8 key (257 INODE_REF 258) itemoff 15787 itemsize 14
[ 3845.737836] index 2 name_len 4
[ 3845.737837] item 9 key (257 DIR_ITEM 2507850652) itemoff 15754 itemsize 33
[ 3845.737838] location key (259 1 0) type 1
[ 3845.737839] transid 10 data_len 0 name_len 3
[ 3845.737840] item 10 key (257 DIR_INDEX 2) itemoff 15721 itemsize 33
[ 3845.737842] location key (259 1 0) type 1
[ 3845.737843] transid 10 data_len 0 name_len 3
[ 3845.737844] item 11 key (258 INODE_ITEM 0) itemoff 15561 itemsize 160
[ 3845.737846] inode generation 9 transid 10 size 8 nbytes 0
[ 3845.737847] block group 0 mode 40755 links 1 uid 0 gid 0
[ 3845.737848] rdev 0 sequence 1 flags 0x0
[ 3845.737849] atime 1764259517.572889464
[ 3845.737850] ctime 1764259517.572889464
[ 3845.737851] mtime 1764259517.572889464
[ 3845.737852] otime 1764259517.572889464
[ 3845.737853] item 12 key (258 INODE_REF 256) itemoff 15547 itemsize 14
[ 3845.737855] index 3 name_len 4
[ 3845.737856] item 13 key (258 DIR_ITEM 1843588421) itemoff 15513 itemsize 34
[ 3845.737857] location key (257 1 0) type 2
[ 3845.737858] transid 10 data_len 0 name_len 4
[ 3845.737860] item 14 key (258 DIR_INDEX 2) itemoff 15479 itemsize 34
[ 3845.737861] location key (257 1 0) type 2
[ 3845.737862] transid 10 data_len 0 name_len 4
[ 3845.737863] item 15 key (259 INODE_ITEM 0) itemoff 15319 itemsize 160
[ 3845.737865] inode generation 10 transid 10 size 0 nbytes 0
[ 3845.737866] block group 0 mode 100600 links 1 uid 0 gid 0
[ 3845.737867] rdev 0 sequence 2 flags 0x0
[ 3845.737868] atime 1764259517.580874966
[ 3845.737869] ctime 1764259517.586121869
[ 3845.737870] mtime 1764259517.580874966
[ 3845.737872] otime 1764259517.580874966
[ 3845.737873] item 16 key (259 INODE_REF 257) itemoff 15306 itemsize 13
[ 3845.737874] index 2 name_len 3
[ 3845.737875] BTRFS error (device dm-0): block=30408704 write time tree block corruption detected
[ 3845.739448] ------------[ cut here ]------------
[ 3845.740092] WARNING: CPU: 5 PID: 30701 at fs/btrfs/disk-io.c:335 btree_csum_one_bio+0x25a/0x270 [btrfs]
[ 3845.741439] Modules linked in: btrfs dm_flakey crc32c_cryptoapi (...)
[ 3845.750626] CPU: 5 UID: 0 PID: 30701 Comm: mount Tainted: G W 6.18.0-rc6-btrfs-next-218+ #1 PREEMPT(full)
[ 3845.752414] Tainted: [W]=WARN
[ 3845.752828] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
[ 3845.754499] RIP: 0010:btree_csum_one_bio+0x25a/0x270 [btrfs]
[ 3845.755460] Code: 31 f6 48 89 (...)
[ 3845.758685] RSP: 0018:ffffa8d9c5677678 EFLAGS: 00010246
[ 3845.759450] RAX: 0000000000000000 RBX: ffff92650e6d4738 RCX: 0000000000000000
[ 3845.760309] RDX: 0000000000000000 RSI: ffffffff9aab45b9 RDI: ffff9264c4748000
[ 3845.761239] RBP: ffff9264d4324000 R08: 0000000000000000 R09: ffffa8d9c5677468
[ 3845.762607] R10: ffff926bdc1fffa8 R11: 0000000000000003 R12: ffffa8d9c5677680
[ 3845.764099] R13: 0000000000004000 R14: ffff9264dd624000 R15: ffff9264d978aba8
[ 3845.765094] FS: 00007f751fa5a840(0000) GS:ffff926c42a82000(0000) knlGS:0000000000000000
[ 3845.766226] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3845.766970] CR2: 0000558df1815380 CR3: 000000010ed88003 CR4: 0000000000370ef0
[ 3845.768009] Call Trace:
[ 3845.768392] <TASK>
[ 3845.768714] btrfs_submit_bbio+0x6ee/0x7f0 [btrfs]
[ 3845.769640] ? write_one_eb+0x28e/0x340 [btrfs]
[ 3845.770588] btree_write_cache_pages+0x2f0/0x550 [btrfs]
[ 3845.771286] ? alloc_extent_state+0x19/0x100 [btrfs]
[ 3845.771967] ? merge_next_state+0x1a/0x90 [btrfs]
[ 3845.772586] ? set_extent_bit+0x233/0x8b0 [btrfs]
[ 3845.773198] ? xas_load+0x9/0xc0
[ 3845.773589] ? xas_find+0x14d/0x1a0
[ 3845.773969] do_writepages+0xc6/0x160
[ 3845.774367] filemap_fdatawrite_wbc+0x48/0x60
[ 3845.775003] __filemap_fdatawrite_range+0x5b/0x80
[ 3845.775902] btrfs_write_marked_extents+0x61/0x170 [btrfs]
[ 3845.776707] btrfs_write_and_wait_transaction+0x4e/0xc0 [btrfs]
[ 3845.777379] ? _raw_spin_unlock_irqrestore+0x23/0x40
[ 3845.777923] btrfs_commit_transaction+0x5ea/0xd20 [btrfs]
[ 3845.778551] ? _raw_spin_unlock+0x15/0x30
[ 3845.778986] ? release_extent_buffer+0x34/0x160 [btrfs]
[ 3845.779659] btrfs_recover_log_trees+0x7a3/0x7c0 [btrfs]
[ 3845.780416] ? __pfx_replay_one_buffer+0x10/0x10 [btrfs]
[ 3845.781499] open_ctree+0x10bb/0x15f0 [btrfs]
[ 3845.782194] btrfs_get_tree.cold+0xb/0x16c [btrfs]
[ 3845.782764] ? fscontext_read+0x15c/0x180
[ 3845.783202] ? rw_verify_area+0x50/0x180
[ 3845.783667] vfs_get_tree+0x25/0xd0
[ 3845.784047] vfs_cmd_create+0x59/0xe0
[ 3845.784458] __do_sys_fsconfig+0x4f6/0x6b0
[ 3845.784914] do_syscall_64+0x50/0x1220
[ 3845.785340] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 3845.785980] RIP: 0033:0x7f751fc7f4aa
[ 3845.786759] Code: 73 01 c3 48 (...)
[ 3845.789951] RSP: 002b:00007ffcdba45dc8 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
[ 3845.791402] RAX: ffffffffffffffda RBX: 000055ccc8291c20 RCX: 00007f751fc7f4aa
[ 3845.792688] RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003
[ 3845.794308] RBP: 000055ccc8292120 R08: 0000000000000000 R09: 0000000000000000
[ 3845.795829] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 3845.797183] R13: 00007f751fe11580 R14: 00007f751fe1326c R15: 00007f751fdf8a23
[ 3845.798633] </TASK>
[ 3845.799067] ---[ end trace 0000000000000000 ]---
[ 3845.800215] BTRFS: error (device dm-0) in btrfs_commit_transaction:2553: errno=-5 IO failure (Error while writing out transaction)
[ 3845.801860] BTRFS warning (device dm-0 state E): Skipping commit of aborted transaction.
[ 3845.802815] BTRFS error (device dm-0 state EA): Transaction aborted (error -5)
[ 3845.803728] BTRFS: error (device dm-0 state EA) in cleanup_transaction:2036: errno=-5 IO failure
[ 3845.805374] BTRFS: error (device dm-0 state EA) in btrfs_replay_log:2083: errno=-5 IO failure (Failed to recover log tree)
[ 3845.807919] BTRFS error (device dm-0 state EA): open_ctree failed: -5

Fix this by never logging a conflicting inode that is a directory and was
moved in the current transaction (its last_unlink_trans equals the current
transaction) and instead fallback to a transaction commit.

A test case for fstests will follow soon.

Reported-by: Vyacheslav Kovalevsky <slva.kovalevskiy.2014@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/7bbc9419-5c56-450a-b5a0-efeae7457113@gmail.com/
CC: stable@vger.kernel.org # 6.1+
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>
---
fs/btrfs/tree-log.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)

--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -5734,6 +5734,33 @@ static int conflicting_inode_is_dir(stru
return ret;
}

+static bool can_log_conflicting_inode(const struct btrfs_trans_handle *trans,
+ const struct btrfs_inode *inode)
+{
+ if (!S_ISDIR(inode->vfs_inode.i_mode))
+ return true;
+
+ if (inode->last_unlink_trans < trans->transid)
+ return true;
+
+ /*
+ * If this is a directory and its unlink_trans is not from a past
+ * transaction then we must fallback to a transaction commit in order
+ * to avoid getting a directory with 2 hard links after log replay.
+ *
+ * This happens if a directory A is renamed, moved from one parent
+ * directory to another one, a new file is created in the old parent
+ * directory with the old name of our directory A, the new file is
+ * fsynced, then we moved the new file to some other parent directory
+ * and fsync again the new file. This results in a log tree where we
+ * logged that directory A existed, with the INODE_REF item for the
+ * new location but without having logged its old parent inode, so
+ * that on log replay we add a new link for the new location but the
+ * old link remains, resulting in a link count of 2.
+ */
+ return false;
+}
+
static int add_conflicting_inode(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_path *path,
@@ -5837,6 +5864,11 @@ static int add_conflicting_inode(struct
return 0;
}

+ if (!can_log_conflicting_inode(trans, inode)) {
+ btrfs_add_delayed_iput(inode);
+ return BTRFS_LOG_FORCE_COMMIT;
+ }
+
btrfs_add_delayed_iput(inode);

ino_elem = kmalloc(sizeof(*ino_elem), GFP_NOFS);
@@ -5901,6 +5933,12 @@ static int log_conflicting_inodes(struct
break;
}

+ if (!can_log_conflicting_inode(trans, inode)) {
+ btrfs_add_delayed_iput(inode);
+ ret = BTRFS_LOG_FORCE_COMMIT;
+ break;
+ }
+
/*
* Always log the directory, we cannot make this
* conditional on need_log_inode() because the directory