From: Matthew Wilcox <willy@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: cluster-devel@redhat.com, linux-kernel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-xfs@vger.kernel.org, linux-mm@kvack.org,
ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org,
linux-btrfs@vger.kernel.org
Subject: Re: [f2fs-dev] [PATCH 04/12] mm: Add readahead address space operation
Date: Thu, 30 Jan 2020 00:00:13 -0800 [thread overview]
Message-ID: <20200130080013.GK6615@bombadil.infradead.org> (raw)
In-Reply-To: <20200129002456.GH18610@dread.disaster.area>
On Wed, Jan 29, 2020 at 11:24:56AM +1100, Dave Chinner wrote:
> 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.
Yup. I originally had:
while (left--) ...
decided that was too confusing and didn't quite complete that thought.
_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
next prev parent reply other threads:[~2020-01-30 8:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-25 1:35 [f2fs-dev] [PATCH 00/12] Change readahead API Matthew Wilcox
2020-01-25 1:35 ` [f2fs-dev] [PATCH 03/12] readahead: Put pages in cache earlier Matthew Wilcox
2020-01-25 19:44 ` Matthew Wilcox
2020-01-25 1:35 ` [f2fs-dev] [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 [this message]
2020-01-25 1:35 ` [f2fs-dev] [PATCH 10/12] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-02-13 4:38 ` [f2fs-dev] [PATCH 00/12] Change readahead API Andrew Morton
2020-02-13 13:43 ` Matthew Wilcox
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200130080013.GK6615@bombadil.infradead.org \
--to=willy@infradead.org \
--cc=cluster-devel@redhat.com \
--cc=david@fromorbit.com \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-erofs@lists.ozlabs.org \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-f2fs-devel@lists.sourceforge.net \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-xfs@vger.kernel.org \
--cc=ocfs2-devel@oss.oracle.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).