linux-kernel - Re: [PATCH v3 1/6] block: Rework bio

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Message-ID: <c3102f97-df59-4859-9af1-d241a357d02f@suse.de>
Date: Tue, 5 Nov 2024 08:21:28 +0100
From: Hannes Reinecke <hare@...e.de>
To: John Garry <john.g.garry@...cle.com>, axboe@...nel.dk, song@...nel.org,
 yukuai3@...wei.com, hch@....de
Cc: martin.petersen@...cle.com, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
 Johannes.Thumshirn@....com
Subject: Re: [PATCH v3 1/6] block: Rework bio_split() return value

On 10/31/24 10:59, John Garry wrote:
> Instead of returning an inconclusive value of NULL for an error in calling
> bio_split(), return a ERR_PTR() always.
> 
> Also remove the BUG_ON() calls, and WARN_ON_ONCE() instead. Indeed, since
> almost all callers don't check the return code from bio_split(), we'll
> crash anyway (for those failures).
> 
> Fix up the only user which checks bio_split() return code today (directly
> or indirectly), blk_crypto_fallback_split_bio_if_needed(). The md/bcache
> code does check the return code in cached_dev_cache_miss() ->
> bio_next_split() -> bio_split(), but only to see if there was a split, so
> there would be no change in behaviour here (when returning a ERR_PTR()).
> 
> Reviewed-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
> Signed-off-by: John Garry <john.g.garry@...cle.com>
> ---
>   block/bio.c                 | 10 ++++++----
>   block/blk-crypto-fallback.c |  2 +-
>   2 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 95e2ee14cea2..7a93724e4a49 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1740,16 +1740,18 @@ struct bio *bio_split(struct bio *bio, int sectors,
>   {
>   	struct bio *split;
>   
> -	BUG_ON(sectors <= 0);
> -	BUG_ON(sectors >= bio_sectors(bio));
> +	if (WARN_ON_ONCE(sectors <= 0))
> +		return ERR_PTR(-EINVAL);
> +	if (WARN_ON_ONCE(sectors >= bio_sectors(bio)))
> +		return ERR_PTR(-EINVAL);
>   
>   	/* Zone append commands cannot be split */
>   	if (WARN_ON_ONCE(bio_op(bio) == REQ_OP_ZONE_APPEND))
> -		return NULL;
> +		return ERR_PTR(-EINVAL);
>   
>   	split = bio_alloc_clone(bio->bi_bdev, bio, gfp, bs);
>   	if (!split)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>   
>   	split->bi_iter.bi_size = sectors << 9;
>   
> diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
> index b1e7415f8439..29a205482617 100644
> --- a/block/blk-crypto-fallback.c
> +++ b/block/blk-crypto-fallback.c
> @@ -226,7 +226,7 @@ static bool blk_crypto_fallback_split_bio_if_needed(struct bio **bio_ptr)
>   
>   		split_bio = bio_split(bio, num_sectors, GFP_NOIO,
>   				      &crypto_bio_split);
> -		if (!split_bio) {
> +		if (IS_ERR(split_bio)) {
>   			bio->bi_status = BLK_STS_RESOURCE;
>   			return false;
>   		}

Don't you need to modify block/bounce.c, too?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich