Btrfs: Fix leaf reference cache miss

Due to the optimization for truncate, tree leaves only containing
checksum items can be deleted without being COW'ed first. This causes
reference cache misses. The way to fix the miss is create cache
entries for tree leaves only contain checksum.

This patch also fixes a -EEXIST issue in shared reference cache.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ab36769c356c..280ac1aa9b6d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1151,6 +1151,14 @@ int btrfs_cache_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                 }
 
                 ret = btrfs_add_leaf_ref(root, ref, shared);
+                if (ret == -EEXIST && shared) {
+                        struct btrfs_leaf_ref *old;
+                        old = btrfs_lookup_leaf_ref(root, ref->bytenr);
+                        BUG_ON(!old);
+                        btrfs_remove_leaf_ref(root, old);
+                        btrfs_free_leaf_ref(root, old);
+                        ret = btrfs_add_leaf_ref(root, ref, shared);
+                }
                 WARN_ON(ret);
                 btrfs_free_leaf_ref(root, ref);
         }