Nikolay Borisov 於 2019-03-25 17:35 寫到:
On 25.03.19 г. 11:06 ч., robbieko wrote:
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;
+ }
+
Looking at the code it seems this function can only be called from
btrfs_write_dirty_block_groups, since its other caller
btrfs_setup_space_cache already checks if SPACE_CACHE option is used.
IMO this patch is fine if we aren't using v1 space cache no point in
executing that function however.
However, why is it necessary to do the cache_generation check, isn't it
sufficient to predicate the execution only on SPACE_CACHE mount option?
When superblock cache_generation != -1,
it means that space_cache=v1 has been used.
If we have used space_cache=v1 before,
we will generate a free space cache inode,
which will take up space, so we must free up
the space occupied by the free space inode.
Thanks.
again:
inode = lookup_free_space_inode(fs_info, block_group, path);
if (IS_ERR(inode) && PTR_ERR(inode) != -ENOENT) {
