From: Naohiro Aota naohiro.aota@wdc.com
[ 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@suse.com Reviewed-by: Johannes Thumshirn johannes.thumshirn@wdc.com Signed-off-by: Naohiro Aota naohiro.aota@wdc.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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;