From: Naohiro Aota <naohiro.aota@xxxxxxx>
[ Upstream commit e75f9fd194090e69c5ffd856ba89160683d343da ]
Commit 6e37d2459941 ("btrfs: zoned: fix deadlock on log sync") pointed out
a deadlock warning and removed mutex_{lock,unlock} of fs_info::tree_root->log_mutex.
While it looks like it always cause a deadlock, we didn't see actual
deadlock in fstests runs. The reason is log_root_tree->log_mutex !=
fs_info->tree_root->log_mutex, not taking the same lock. So, the warning
was actually a false-positive.
Since btrfs_alloc_log_tree_node() is protected only by
fs_info->tree_root->log_mutex, we can (and should) move the code out of
the lock scope of log_root_tree->log_mutex and silence the warning.
Fixes: 6e37d2459941 ("btrfs: zoned: fix deadlock on log sync")
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/btrfs/tree-log.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 92a368627791..72c4b66ed516 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3165,20 +3165,22 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
*/
mutex_unlock(&root->log_mutex);
- btrfs_init_log_ctx(&root_log_ctx, NULL);
-
- mutex_lock(&log_root_tree->log_mutex);
-
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(&log_root_tree->log_mutex);
+ mutex_unlock(&fs_info->tree_log_mutex);
goto out;
}
}
+ mutex_unlock(&fs_info->tree_root->log_mutex);
}
+ btrfs_init_log_ctx(&root_log_ctx, NULL);
+
+ mutex_lock(&log_root_tree->log_mutex);
+
index2 = log_root_tree->log_transid % 2;
list_add_tail(&root_log_ctx.list, &log_root_tree->log_ctxs[index2]);
root_log_ctx.log_transid = log_root_tree->log_transid;
--
2.30.2
