btrfs: fix calculation of the global block reserve's size

At btrfs_update_global_block_rsv(), we are assuming an unlink operation
uses 5 metadata units, but that's not true anymore, it uses 6 since the
commit bca4ad7c0b54 ("btrfs: reserve correct number of items for unlink
and rmdir"). So update the code and comments to consider 6 units.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c
index 90b8088e8facdfe9536323ae01a4ba8aaf37ccf7..6edcb32ed4c9e5c007adb12c35e0e363a64f6a66 100644 (file)
--- a/fs/btrfs/block-rsv.c
+++ b/fs/btrfs/block-rsv.c
@@ -350,14 +350,14 @@ void btrfs_update_global_block_rsv(struct btrfs_fs_info *fs_info)
 
        /*
         * But we also want to reserve enough space so we can do the fallback
-        * global reserve for an unlink, which is an additional 5 items (see the
+        * global reserve for an unlink, which is an additional 6 items (see the
         * comment in __unlink_start_trans for what we're modifying.)
         *
         * But we also need space for the delayed ref updates from the unlink,
-        * so its 10, 5 for the actual operation, and 5 for the delayed ref
+        * so its 12, 6 for the actual operation, and 6 for the delayed ref
         * updates.
         */
-       min_items += 10;
+       min_items += 12;
 
        num_bytes = max_t(u64, num_bytes,
                          btrfs_calc_insert_metadata_size(fs_info, min_items));