Lockdep with fstests test-case btrfs/041 detected a unsafe locking
scenario when we allocate the log node on a zoned filesystem.
btrfs/041
============================================
WARNING: possible recursive locking detected
5.11.0-rc7+ #939 Not tainted
--------------------------------------------
xfs_io/698 is trying to acquire lock:
ffff88810cd673a0 (&root->log_mutex){+.+.}-{3:3}, at:
btrfs_sync_log+0x3d1/0xee0 [btrfs]
but task is already holding lock:
ffff88810b0fc3a0 (&root->log_mutex){+.+.}-{3:3}, at:
btrfs_sync_log+0x313/0xee0 [btrfs]
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&root->log_mutex);
lock(&root->log_mutex);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by xfs_io/698:
#0: ffff88810cd66620 (sb_internal){.+.+}-{0:0}, at:
btrfs_sync_file+0x2c3/0x570 [btrfs]
#1: ffff88810b0fc3a0 (&root->log_mutex){+.+.}-{3:3}, at:
btrfs_sync_log+0x313/0xee0 [btrfs]
stack backtrace:
CPU: 0 PID: 698 Comm: xfs_io Not tainted 5.11.0-rc7+ #939
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
Call Trace:
dump_stack+0x77/0x97
__lock_acquire.cold+0xb9/0x32a
lock_acquire+0xb5/0x400
? btrfs_sync_log+0x3d1/0xee0 [btrfs]
__mutex_lock+0x7b/0x8d0
? btrfs_sync_log+0x3d1/0xee0 [btrfs]
? btrfs_sync_log+0x3d1/0xee0 [btrfs]
? find_first_extent_bit+0x9f/0x100 [btrfs]
? __mutex_unlock_slowpath+0x35/0x270
btrfs_sync_log+0x3d1/0xee0 [btrfs]
btrfs_sync_file+0x3a8/0x570 [btrfs]
__x64_sys_fsync+0x34/0x60
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f1e856b8ecb
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8
b3 f6 ff ff 8b 7c 24 0c 41 89 c0 b8 4a 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35
44 89 c7 89 44 24 0c e8 11 f7 ff ff 8b 44
RSP: 002b:00007ffde89011b0 EFLAGS: 00000293 ORIG_RAX: 000000000000004a
RAX: ffffffffffffffda RBX: 0000557ef97886c0 RCX: 00007f1e856b8ecb
RDX: 0000000000000002 RSI: 0000557ef97886e0 RDI: 0000000000000003
RBP: 0000557ef97886e0 R08: 0000000000000000 R09: 0000000000000003
R10: fffffffffffff50e R11: 0000000000000293 R12: 0000000000000001
R13: 0000557ef97886c0 R14: 0000000000000001 R15: 0000557ef976e2a0
This happens, because we are taking the ->log_mutex albeit it has already
been locked.
Also while at it, fix the bogus unlock of the tree_log_mutex in the error
handling.
Fixes: 3ddebf27fcd3 ("btrfs: zoned: reorder log node allocation on zoned
filesystem")
Cc: Filipe Manana <[email protected]>
Cc: Naohiro Aota <[email protected]>
Signed-off-by: Johannes Thumshirn <[email protected]>
---
fs/btrfs/tree-log.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index d90695c1ab6c..2f1acc9aea9e 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3174,16 +3174,13 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
root_log_ctx.log_transid = log_root_tree->log_transid;
if (btrfs_is_zoned(fs_info)) {
- mutex_lock(&fs_info->tree_root->log_mutex);
if (!log_root_tree->node) {
ret = btrfs_alloc_log_tree_node(trans, log_root_tree);
if (ret) {
- mutex_unlock(&fs_info->tree_log_mutex);
mutex_unlock(&log_root_tree->log_mutex);
goto out;
}
}
- mutex_unlock(&fs_info->tree_root->log_mutex);
}
/*
--
2.30.0
