Re: [PATCH RFC 2/8] btrfs: use super write guard in btrfs_reclaim_bgs_work()

Qu Wenruo
2025-11-04T20:42:45Z

在 2025/11/4 22:42, Christian Brauner 写道:
> Signed-off-by: Christian Brauner <brauner@kernel.org>
> ---
> fs/btrfs/block-group.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index 5322ef2ae015..8284b9435758 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -1850,7 +1850,7 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
> if (!btrfs_should_reclaim(fs_info))
> return;
>
> - sb_start_write(fs_info->sb);
> + guard(super_write)(fs_info->sb);
>
> if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) {
> sb_end_write(fs_info->sb);

This one is still left using the old scheme, and there is another one in
the mutex_trylock() branch.

I'm wondering how safe is the new scope based auto freeing.

Like when the freeing function is called? Will it break the existing
freeing/locking sequence in other locations?

For this call site, sb_end_write() is always called last so it's fine.

Thanks,
Qu

> @@ -2030,7 +2030,6 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
> list_splice_tail(&retry_list, &fs_info->reclaim_bgs);
> spin_unlock(&fs_info->unused_bgs_lock);
> btrfs_exclop_finish(fs_info);
> - sb_end_write(fs_info->sb);
> }
>
> void btrfs_reclaim_bgs(struct btrfs_fs_info *fs_info)
>