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Date: Tue, 12 Mar 2024 08:51:35 -0600
From: Keith Busch <kbusch@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Chandan Babu R <chandanbabu@kernel.org>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-xfs@vger.kernel.org
Subject: Re: [PATCH 2/5] block: add a bio_chain_and_submit helper
Message-ID: <ZfBr91m4oQS_VYFg@kbusch-mbp.mynextlight.net>
References: <20240312144532.1044427-1-hch@lst.de>
 <20240312144532.1044427-3-hch@lst.de>
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In-Reply-To: <20240312144532.1044427-3-hch@lst.de>

On Tue, Mar 12, 2024 at 08:45:28AM -0600, Christoph Hellwig wrote:
> +struct bio *bio_chain_and_submit(struct bio *prev, struct bio *new)
>  {
> -	struct bio *new = bio_alloc(bdev, nr_pages, opf, gfp);
> -
> -	if (bio) {
> -		bio_chain(bio, new);
> -		submit_bio(bio);
> +	if (prev) {
> +		bio_chain(prev, new);
> +		submit_bio(prev);
>  	}
> -
>  	return new;
>  }
> +EXPORT_SYMBOL_GPL(bio_chain_and_submit);
> +
> +struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
> +		unsigned int nr_pages, blk_opf_t opf, gfp_t gfp)
> +{
> +	return bio_chain_and_submit(bio, bio_alloc(bdev, nr_pages, opf, gfp));
> +}

I realize you're not changing any behavior here, but I want to ask, is
bio_alloc() always guaranteed to return a valid bio? It sure looks like
it can return NULL under some uncommon conditions, but I can't find
anyone checking the result. So I guess it's safe?