Re: [PATCH v2 05/18] btrfs: do not allow free space tree rebuild on extent tree v2

Anand Jain
2023-11-15T09:50:07Z

On 11/9/23 03:08, Josef Bacik wrote:
> We currently don't allow these options to be set if we're extent tree v2
> via the mount option parsing. However when we switch to the new mount
> API we'll no longer have the super block loaded, so won't be able to
> make this distinction at mount option parsing time. Address this by
> checking for extent tree v2 at the point where we make the decision to
> rebuild the free space tree.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> fs/btrfs/disk-io.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index b486cbec492b..072c45811c41 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -2951,7 +2951,8 @@ int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info)
> bool rebuild_free_space_tree = false;
>
> if (btrfs_test_opt(fs_info, CLEAR_CACHE) &&
> - btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
> + btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
> + !btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
> rebuild_free_space_tree = true;
> } else if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
> !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID)) {

If there is v3 you can consider to add a comment similar to that
is in btrfs_parse_options().
Also, IMO, it is a good idea to include a btrfs_info() statement
to indicate that the clear_cache option is ignored.

--------------------
case Opt_clear_cache:
/*
* We cannot clear the free space tree with
extent tree
* v2, ignore this option.
*/
if (btrfs_fs_incompat(info, EXTENT_TREE_V2))
break;
btrfs_set_and_info(info, CLEAR_CACHE,
"force clearing of disk cache");
break;
--------------------

Thanks, Anand