In case of (cow && (p->keep_locks || p->lowest_level)), write_lock_level
is the max level, and we should grab write lock of root node from the very
beginning.
Signed-off-by: Liu Bo <bo....@linux.alibaba.com>
---
fs/btrfs/ctree.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index cf34eca41d4e..f7c3f581f647 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2633,20 +2633,23 @@ static struct extent_buffer
*btrfs_search_slot_get_root(struct btrfs_root *root,
goto out;
}
- /*
- * we don't know the level of the root node until we actually
- * have it read locked
- */
- b = btrfs_read_lock_root_node(root);
- level = btrfs_header_level(b);
- if (level > write_lock_level)
- goto out;
+ if (write_lock_level < BTRFS_MAX_LEVEL) {
+ /*
+ * we don't know the level of the root node until we actually
+ * have it read locked
+ */
+ b = btrfs_read_lock_root_node(root);
+ level = btrfs_header_level(b);
+ if (level > write_lock_level)
+ goto out;
+
+ /*
+ * whoops, must trade for write lock
+ */
+ btrfs_tree_read_unlock(b);
+ free_extent_buffer(b);
+ }
- /*
- * whoops, must trade for write lock
- */
- btrfs_tree_read_unlock(b);
- free_extent_buffer(b);
b = btrfs_lock_root_node(root);
root_lock = BTRFS_WRITE_LOCK;
/*
--
1.8.3.1
--
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