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From: Andrew Morton <akpm@linux-foundation.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
	linux-kernel@vger.kernel.org,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	xfs@oss.sgi.com
Subject: Re: [PATCH 3/4] writeback: pay attention to wbc->nr_to_write in write_cache_pages
Date: Thu, 29 Apr 2010 14:39:31 -0700	[thread overview]
Message-ID: <20100429143931.331c2bab.akpm@linux-foundation.org> (raw)
In-Reply-To: <1271731314-5893-4-git-send-email-david@fromorbit.com>

On Tue, 20 Apr 2010 12:41:53 +1000
Dave Chinner <david@fromorbit.com> wrote:

> If a filesystem writes more than one page in ->writepage, write_cache_pages
> fails to notice this and continues to attempt writeback when wbc->nr_to_write
> has gone negative - this trace was captured from XFS:
> 
> 
>     wbc_writeback_start: towrt=1024
>     wbc_writepage: towrt=1024
>     wbc_writepage: towrt=0
>     wbc_writepage: towrt=-1
>     wbc_writepage: towrt=-5
>     wbc_writepage: towrt=-21
>     wbc_writepage: towrt=-85
> 

Bug.

AFAIT it's a regression introduced by

: commit 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4
: Author:     Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
: AuthorDate: Thu Oct 16 10:09:17 2008 -0400
: Commit:     Theodore Ts'o <tytso@mit.edu>
: CommitDate: Thu Oct 16 10:09:17 2008 -0400
: 
:     vfs: Add no_nrwrite_index_update writeback control flag

I suggest that what you do here is remove the local `nr_to_write' from
write_cache_pages() and go back to directly using wbc->nr_to_write
within the loop.

And thus we restore the convention that if the fs writes back more than
a single page, it subtracts (nr_written - 1) from wbc->nr_to_write.

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WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	xfs@oss.sgi.com,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	"Theodore Ts'o" <tytso@mit.edu>
Subject: Re: [PATCH 3/4] writeback: pay attention to wbc->nr_to_write in write_cache_pages
Date: Thu, 29 Apr 2010 14:39:31 -0700	[thread overview]
Message-ID: <20100429143931.331c2bab.akpm@linux-foundation.org> (raw)
In-Reply-To: <1271731314-5893-4-git-send-email-david@fromorbit.com>

On Tue, 20 Apr 2010 12:41:53 +1000
Dave Chinner <david@fromorbit.com> wrote:

> If a filesystem writes more than one page in ->writepage, write_cache_pages
> fails to notice this and continues to attempt writeback when wbc->nr_to_write
> has gone negative - this trace was captured from XFS:
> 
> 
>     wbc_writeback_start: towrt=1024
>     wbc_writepage: towrt=1024
>     wbc_writepage: towrt=0
>     wbc_writepage: towrt=-1
>     wbc_writepage: towrt=-5
>     wbc_writepage: towrt=-21
>     wbc_writepage: towrt=-85
> 

Bug.

AFAIT it's a regression introduced by

: commit 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4
: Author:     Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
: AuthorDate: Thu Oct 16 10:09:17 2008 -0400
: Commit:     Theodore Ts'o <tytso@mit.edu>
: CommitDate: Thu Oct 16 10:09:17 2008 -0400
: 
:     vfs: Add no_nrwrite_index_update writeback control flag

I suggest that what you do here is remove the local `nr_to_write' from
write_cache_pages() and go back to directly using wbc->nr_to_write
within the loop.

And thus we restore the convention that if the fs writes back more than
a single page, it subtracts (nr_written - 1) from wbc->nr_to_write.


  parent reply	other threads:[~2010-04-29 21:38 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-20  2:41 [PATCH 0/4] writeback: tracing and wbc->nr_to_write fixes Dave Chinner
2010-04-20  2:41 ` Dave Chinner
2010-04-20  2:41 ` [PATCH 1/4] writeback: initial tracing support Dave Chinner
2010-04-20  2:41   ` Dave Chinner
2010-05-21 15:06   ` Christoph Hellwig
2010-05-21 15:06     ` Christoph Hellwig
2010-04-20  2:41 ` [PATCH 2/4] writeback: Add tracing to balance_dirty_pages Dave Chinner
2010-04-20  2:41   ` Dave Chinner
2010-04-20  2:41 ` [PATCH 3/4] writeback: pay attention to wbc->nr_to_write in write_cache_pages Dave Chinner
2010-04-20  2:41   ` Dave Chinner
2010-04-22 19:07   ` Jan Kara
2010-04-22 19:07     ` Jan Kara
2010-04-25  3:33   ` tytso
2010-04-25  3:33     ` tytso
2010-04-25  3:33     ` tytso
2010-04-26  1:49     ` Dave Chinner
2010-04-26  1:49       ` Dave Chinner
2010-04-26  1:49       ` Dave Chinner
2010-04-26  2:43       ` tytso
2010-04-26  2:43         ` tytso
2010-04-26  2:45         ` tytso
2010-04-26  2:45           ` tytso
2010-04-27  3:30         ` Dave Chinner
2010-04-27  3:30           ` Dave Chinner
2010-04-29 21:39   ` Andrew Morton [this message]
2010-04-29 21:39     ` Andrew Morton
2010-04-30  6:01     ` Aneesh Kumar K. V
2010-04-30  6:01       ` Aneesh Kumar K. V
2010-04-30 19:43       ` Andrew Morton
2010-04-30 19:43         ` Andrew Morton
2010-05-01 19:47         ` tytso
2010-05-01 19:47           ` tytso
2010-04-20  2:41 ` [PATCH 4/4] xfs: remove nr_to_write writeback windup Dave Chinner
2010-04-20  2:41   ` Dave Chinner
2010-04-22 19:09   ` Jan Kara
2010-04-22 19:09     ` Jan Kara
2010-04-26  0:46     ` Dave Chinner
2010-04-26  0:46       ` Dave Chinner
2010-04-20  3:40 ` [PATCH 5/4] writeback: limit write_cache_pages integrity scanning to current EOF Dave Chinner
2010-04-20  3:40   ` Dave Chinner
2010-04-20 23:28   ` Jamie Lokier
2010-04-20 23:28     ` Jamie Lokier
2010-04-20 23:31     ` Dave Chinner
2010-04-20 23:31       ` Dave Chinner
2010-04-22 19:13   ` Jan Kara
2010-04-22 19:13     ` Jan Kara
2010-04-20 12:02 ` [PATCH 0/4] writeback: tracing and wbc->nr_to_write fixes Richard Kennedy
2010-04-20 12:02   ` Richard Kennedy
2010-04-20 23:29   ` Dave Chinner
2010-04-20 23:29     ` Dave Chinner
2010-05-21 15:05 ` Christoph Hellwig
2010-05-21 15:05   ` Christoph Hellwig
2010-05-22  0:09   ` Dave Chinner
2010-05-22  0:09     ` Dave Chinner

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