Re: [PATCH 3/4] btrfs: switch GFP_NOFS to GFP_KERNEL in scrub_setup_recheck_block

[Anand Jain <anand.jain@oracle.com>]

On 18/10/2022 22:27, David Sterba wrote:
> There's only one caller that calls scrub_setup_recheck_block in the
> memalloc_nofs_save/_restore protection so it's effectively already
> GFP_NOFS and it's safe to use GFP_KERNEL.
> 
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>   fs/btrfs/scrub.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 9e3b2e60e571..2fc70a2cc7fe 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -1491,7 +1491,7 @@ static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
>   			return -EIO;
>   		}
>   
> -		recover = kzalloc(sizeof(struct scrub_recover), GFP_NOFS);
> +		recover = kzalloc(sizeof(struct scrub_recover), GFP_KERNEL);


I didn't get why GFP_KERNEL is better here, or would it make any 
difference, given that we are already (and rightly) in the 
memalloc_nofs_save() scope.

Thanks, Anand


>   		if (!recover) {
>   			btrfs_put_bioc(bioc);
>   			btrfs_bio_counter_dec(fs_info);
> @@ -1514,7 +1514,7 @@ static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
>   			sblock = sblocks_for_recheck[mirror_index];
>   			sblock->sctx = sctx;
>   
> -			sector = alloc_scrub_sector(sblock, logical, GFP_NOFS);
> +			sector = alloc_scrub_sector(sblock, logical, GFP_KERNEL);
>   			if (!sector) {
>   				spin_lock(&sctx->stat_lock);
>   				sctx->stat.malloc_errors++;