From: Matthew Wilcox <willy@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 12/12] iomap: Convert from readpages to readahead
Date: Fri, 31 Jan 2020 01:44:18 -0800 [thread overview]
Message-ID: <20200131094418.GA4437@bombadil.infradead.org> (raw)
In-Reply-To: <20200129013839.GL18610@dread.disaster.area>
On Wed, Jan 29, 2020 at 12:38:39PM +1100, Dave Chinner wrote:
> On Fri, Jan 24, 2020 at 05:35:53PM -0800, Matthew Wilcox wrote:
> > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> > Use the new readahead operation in XFS and iomap.
> > + if (ctx.cur_page && ctx.cur_page_in_bio)
> > put_page(ctx.cur_page);
> > - }
> >
> > - /*
> > - * Check that we didn't lose a page due to the arcance calling
> > - * conventions..
> > - */
> > - WARN_ON_ONCE(!ret && !list_empty(ctx.pages));
> > - return ret;
> > + return length / PAGE_SIZE;
>
> Took me quite some time to get my head around whether this was
> correct or not.
Yes. Unfortunately, this is the most complex of the conversions ;-(
> I'm still not certain in the cases where block size != page size and
> we've got an extent boundary in the middle of the page and had a
> read error on the second extent in the page. In this case,
> ctx.cur_page_in_bio is true so we drop the readahead reference to
> the page. Also, length is not a multiple of page size, and so the
> nr_pages value returned includes the partial page that we have IO
> underway on.
>
> That, I think, leads to both a double unlock and a double put_page()
> of the partial page in question.
But C division rounds down. So we neither unlock, nor put_page() the
page which was in the bio ... do we?
next prev parent reply other threads:[~2020-01-31 9:44 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
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 [this message]
2020-02-13 4:38 ` [PATCH 00/12] Change readahead API Andrew Morton
2020-02-13 13:43 ` Matthew Wilcox
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