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From: Matthew Wilcox <willy@infradead.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org,
	Kundan Kumar <kundan.kumar@samsung.com>,
	Christoph Hellwig <hch@lst.de>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Gavin Shan <gshan@redhat.com>
Subject: Re: [PATCH] block: fix adding folio to bio
Date: Wed, 12 Mar 2025 12:19:12 +0000	[thread overview]
Message-ID: <Z9F7wOB0PqouJfss@casper.infradead.org> (raw)
In-Reply-To: <20250312113805.2868986-1-ming.lei@redhat.com>

On Wed, Mar 12, 2025 at 07:38:05PM +0800, Ming Lei wrote:
> +++ b/block/bio.c
> @@ -1026,9 +1026,17 @@ EXPORT_SYMBOL(bio_add_page);
>  void bio_add_folio_nofail(struct bio *bio, struct folio *folio, size_t len,
>  			  size_t off)
>  {
> +	struct page *page = &folio->page;
> +
>  	WARN_ON_ONCE(len > UINT_MAX);
> -	WARN_ON_ONCE(off > UINT_MAX);
> -	__bio_add_page(bio, &folio->page, len, off);
> +	if (unlikely(off > UINT_MAX)) {

I think we should probably make this:

	if (unlikely(off + len > UINT_MAX))

because I'm not sure that everything will cope well with an I/O that
crosses the 4GB boundary.

Actually, why bother with the conditional?  Let's just do it always.

 {
+	unsigned long nr = off / PAGE_SIZE;
 	WARN_ON_ONCE(len > UINT_MAX);
-	WARN_ON_ONCE(off > UINT_MAX);
-	__bio_add_page(bio, &folio->page, len, off);
+	off = off % PAGE_SIZE;
+	__bio_add_page(bio, folio_page(folio, nr), len, off);
 }

Also you need to do bio_add_folio(), not just the _nofail variant.

  reply	other threads:[~2025-03-12 12:19 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-12 11:38 [PATCH] block: fix adding folio to bio Ming Lei
2025-03-12 12:19 ` Matthew Wilcox [this message]
2025-03-12 14:02   ` Ming Lei

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