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From: Dave Chinner <david@fromorbit.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-xfs@vger.kernel.org, cluster-devel@redhat.com,
	ocfs2-devel@oss.oracle.com
Subject: Re: [PATCH 04/12] mm: Add readahead address space operation
Date: Wed, 29 Jan 2020 11:24:56 +1100	[thread overview]
Message-ID: <20200129002456.GH18610@dread.disaster.area> (raw)
In-Reply-To: <20200125013553.24899-5-willy@infradead.org>

On Fri, Jan 24, 2020 at 05:35:45PM -0800, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> This replaces ->readpages with a saner interface:
>  - Return the number of pages not read instead of an ignored error code.
>  - Pages are already in the page cache when ->readahead is called.
>  - Implementation looks up the pages in the page cache instead of
>    having them passed in a linked list.
....
> diff --git a/mm/readahead.c b/mm/readahead.c
> index 5a6676640f20..6d65dae6dad0 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -121,7 +121,18 @@ static void read_pages(struct address_space *mapping, struct file *filp,
>  
>  	blk_start_plug(&plug);
>  
> -	if (mapping->a_ops->readpages) {
> +	if (mapping->a_ops->readahead) {
> +		unsigned left = mapping->a_ops->readahead(filp, mapping,
> +				start, nr_pages);
> +
> +		while (left) {
> +			struct page *page = readahead_page(mapping,
> +					start + nr_pages - left - 1);

Off by one? start = 2, nr_pages = 2, left = 1, this looks up the
page at index 2, which is the one we issued IO on, not the one we
"left behind" which is at index 3.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  parent reply	other threads:[~2020-01-29  0:25 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-25  1:35 [PATCH 00/12] Change readahead API Matthew Wilcox
2020-01-25  1:35 ` [PATCH 01/12] mm: Fix the return type of __do_page_cache_readahead Matthew Wilcox
2020-01-25  1:35 ` [PATCH 02/12] readahead: Ignore return value of ->readpages Matthew Wilcox
2020-01-25  1:35 ` [PATCH 03/12] readahead: Put pages in cache earlier Matthew Wilcox
2020-01-25 19:44   ` Matthew Wilcox
2020-01-25  1:35 ` [PATCH 04/12] mm: Add readahead address space operation Matthew Wilcox
2020-01-25  3:57   ` Randy Dunlap
2020-02-01  0:25     ` Matthew Wilcox
2020-01-29  0:24   ` Dave Chinner [this message]
2020-01-30  8:00     ` Matthew Wilcox
2020-01-25  1:35 ` [PATCH 05/12] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-01-25  1:35 ` [PATCH 06/12] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-01-29  0:46   ` Dave Chinner
2020-01-30  8:09     ` Matthew Wilcox
2020-01-31  2:17       ` Dave Chinner
2020-01-25  1:35 ` [PATCH 07/12] erofs: Convert uncompressed files " Matthew Wilcox
2020-01-25  1:53   ` Gao Xiang
2020-01-25 19:09     ` Matthew Wilcox
2020-01-29  0:57   ` Dave Chinner
2020-01-30  8:10     ` Matthew Wilcox
2020-01-25  1:35 ` [PATCH 08/12] erofs: Convert compressed " Matthew Wilcox
2020-01-25  1:35 ` [PATCH 09/12] ext4: Convert " Matthew Wilcox
2020-01-25  1:35 ` [PATCH 10/12] f2fs: " Matthew Wilcox
2020-01-25  1:35 ` [PATCH 11/12] fuse: " Matthew Wilcox
2020-01-29  1:08   ` Dave Chinner
2020-01-30 21:35     ` Matthew Wilcox
2020-01-31  2:19       ` Dave Chinner
2020-01-29 10:50   ` Miklos Szeredi
2020-01-30  7:26     ` Matthew Wilcox
2020-01-25  1:35 ` [PATCH 12/12] iomap: " Matthew Wilcox
2020-01-29  1:38   ` Dave Chinner
2020-01-31  9:44     ` Matthew Wilcox
2020-02-13  4:38 ` [PATCH 00/12] Change readahead API Andrew Morton
2020-02-13 13:43   ` Matthew Wilcox

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