[PATCH] Btrfs: improve unnecessary free space inode update when space_cache=v1 has never been used

[robbieko]

From: Robbie Ko <robbi...@synology.com>

When we have never used space_cache=v1, we don't need to update
the free space inode, and try to free up the space occupied by the
free space inode.

Signed-off-by: Robbie Ko <robbi...@synology.com>
---
 fs/btrfs/extent-tree.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1d49694..d3bba07 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3403,6 +3403,13 @@ static int cache_save_setup(struct 
btrfs_block_group_cache *block_group,
 
        if (trans->aborted)
                return 0;
+
+       if (btrfs_super_cache_generation(fs_info->super_copy) == (u64)-1 &&
+               !btrfs_test_opt(fs_info, SPACE_CACHE)) {
+               dcs = BTRFS_DC_WRITTEN;
+               goto out;
+       }
+
 again:
        inode = lookup_free_space_inode(fs_info, block_group, path);
        if (IS_ERR(inode) && PTR_ERR(inode) != -ENOENT) {
-- 
1.9.1