Re: [PATCH] btrfs: reset block group chunk force if we have to wait

[Filipe Manana <fdmanana@kernel.org>]

On Mon, Jun 13, 2022 at 06:31:17PM -0400, Josef Bacik wrote:
> If you try to force a chunk allocation, but you race with another chunk
> allocation, you will end up waiting on the chunk allocation that just
> occurred and then allocate another chunk.  If you have many threads all
> doing this at once you can way over-allocate chunks.
> 
> Fix this by resetting force to NO_FORCE, that way if we think we need to
> allocate we can, otherwise we don't force another chunk allocation if
> one is already happening.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Looks good, thanks.

> ---
>  fs/btrfs/block-group.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index ede389f2602d..13358fbc1629 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -3761,6 +3761,7 @@ int btrfs_chunk_alloc(struct btrfs_trans_handle *trans, u64 flags,
>  			 * attempt.
>  			 */
>  			wait_for_alloc = true;
> +			force = CHUNK_ALLOC_NO_FORCE;
>  			spin_unlock(&space_info->lock);
>  			mutex_lock(&fs_info->chunk_mutex);
>  			mutex_unlock(&fs_info->chunk_mutex);
> -- 
> 2.26.3
>