From: Andrew Morton <akpm@linux-foundation.org>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>, Jan Kara <jack@suse.cz>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/6] writeback: dont redirty tail an inode with dirty pages
Date: Mon, 12 Jul 2010 15:13:17 -0700 [thread overview]
Message-ID: <20100712151317.bd9d656c.akpm@linux-foundation.org> (raw)
In-Reply-To: <20100712153127.GB30222@localhost>
On Mon, 12 Jul 2010 23:31:27 +0800
Wu Fengguang <fengguang.wu@intel.com> wrote:
> > > + } else if (inode->i_state & I_DIRTY) {
> > > + /*
> > > + * At least XFS will redirty the inode during the
> > > + * writeback (delalloc) and on io completion (isize).
> > > + */
> > > + redirty_tail(inode);
> >
> > I'd drop the mention of XFS here - any filesystem that does delayed
> > allocation or unwritten extent conversion after Io completion will
> > cause this. Perhaps make the comment:
> >
> > /*
> > * Filesystems can dirty the inode during writeback
> > * operations, such as delayed allocation during submission
> > * or metadata updates after data IO completion.
> > */
>
> Thanks, comments updated accordingly.
>
> ---
> writeback: don't redirty tail an inode with dirty pages
>
> This avoids delaying writeback for an expired (XFS) inode with lots of
> dirty pages, but no active dirtier at the moment. Previously we only do
> that for the kupdate case.
>
You didn't actually explain the _reason_ for making this change.
Please always do that.
The patch is... surprisingly complicated, although the end result
looks OK. This is not aided by the partial duplication between
mapping_tagged(PAGECACHE_TAG_DIRTY) and I_DIRTY_PAGES. I don't think
we can easily remove I_DIRTY_PAGES because it's used for the
did-someone-just-dirty-a-page test here.
This code is way too complex and fragile and I fear that anything we do
to it will break something :(
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next prev parent reply other threads:[~2010-07-12 22:13 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-11 2:06 [PATCH 0/6] writeback cleanups and trivial fixes Wu Fengguang
2010-07-11 2:06 ` [PATCH 1/6] writeback: take account of NR_WRITEBACK_TEMP in balance_dirty_pages() Wu Fengguang
2010-07-12 21:52 ` Andrew Morton
2010-07-13 8:58 ` Miklos Szeredi
2010-07-15 14:50 ` Wu Fengguang
2010-07-11 2:06 ` [PATCH 2/6] writeback: reduce calls to global_page_state " Wu Fengguang
2010-07-26 15:19 ` Jan Kara
2010-07-27 3:59 ` Wu Fengguang
2010-07-27 9:12 ` Jan Kara
2010-07-28 2:04 ` Wu Fengguang
2010-08-03 14:55 ` Peter Zijlstra
2010-07-11 2:06 ` [PATCH 3/6] writeback: avoid unnecessary calculation of bdi dirty thresholds Wu Fengguang
2010-07-12 21:56 ` Andrew Morton
2010-07-15 14:55 ` Wu Fengguang
2010-07-19 21:35 ` Andrew Morton
2010-07-20 3:34 ` Wu Fengguang
2010-07-20 4:14 ` Andrew Morton
2010-08-03 15:03 ` Peter Zijlstra
2010-08-03 15:10 ` Wu Fengguang
2010-08-04 16:41 ` Wu Fengguang
2010-08-04 17:10 ` Peter Zijlstra
2010-07-11 2:07 ` [PATCH 4/6] writeback: dont redirty tail an inode with dirty pages Wu Fengguang
2010-07-12 2:01 ` Dave Chinner
2010-07-12 15:31 ` Wu Fengguang
2010-07-12 22:13 ` Andrew Morton [this message]
2010-07-15 15:35 ` Wu Fengguang
2010-07-11 2:07 ` [PATCH 5/6] writeback: fix queue_io() ordering Wu Fengguang
2010-07-12 22:15 ` Andrew Morton
2010-07-11 2:07 ` [PATCH 6/6] writeback: merge for_kupdate and !for_kupdate cases Wu Fengguang
2010-07-12 2:08 ` Dave Chinner
2010-07-12 15:52 ` Wu Fengguang
2010-07-12 22:06 ` Dave Chinner
2010-07-12 22:22 ` Andrew Morton
2010-08-05 16:01 ` Wu Fengguang
2010-07-11 2:44 ` [PATCH 0/6] writeback cleanups and trivial fixes Christoph Hellwig
2010-07-11 2:50 ` Wu Fengguang
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