linux-kernel - [PATCH 5.4 083/129] btrfs: set the correct lockdep class for new nodes

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Date:   Tue,  8 Sep 2020 17:25:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Filipe Manana <fdmanana@...e.com>,
        Nikolay Borisov <nborisov@...e.com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.4 083/129] btrfs: set the correct lockdep class for new nodes

From: Josef Bacik <josef@...icpanda.com>

commit ad24466588ab7d7c879053c5afd919b0c555fec0 upstream.

When flipping over to the rw_semaphore I noticed I'd get a lockdep splat
in replace_path(), which is weird because we're swapping the reloc root
with the actual target root.  Turns out this is because we're using the
root->root_key.objectid as the root id for the newly allocated tree
block when setting the lockdep class, however we need to be using the
actual owner of this new block, which is saved in owner.

The affected path is through btrfs_copy_root as all other callers of
btrfs_alloc_tree_block (which calls init_new_buffer) have root_objectid
== root->root_key.objectid .

CC: stable@...r.kernel.org # 5.4+
Reviewed-by: Filipe Manana <fdmanana@...e.com>
Reviewed-by: Nikolay Borisov <nborisov@...e.com>
Signed-off-by: Josef Bacik <josef@...icpanda.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/extent-tree.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4446,7 +4446,7 @@ btrfs_init_new_buffer(struct btrfs_trans
 		return ERR_PTR(-EUCLEAN);
 	}
 
-	btrfs_set_buffer_lockdep_class(root->root_key.objectid, buf, level);
+	btrfs_set_buffer_lockdep_class(owner, buf, level);
 	btrfs_tree_lock(buf);
 	btrfs_clean_tree_block(buf);
 	clear_bit(EXTENT_BUFFER_STALE, &buf->bflags);