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From: Andrew Morton <akpm@linux-foundation.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, stable@kernel.org,
	torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
	xfs@oss.sgi.com
Subject: Re: [PATCH 1/3] writeback: pay attention to wbc->nr_to_write in write_cache_pages
Date: Wed, 9 Jun 2010 14:09:42 -0700	[thread overview]
Message-ID: <20100609140942.6799c84a.akpm@linux-foundation.org> (raw)
In-Reply-To: <1276043840-1946-2-git-send-email-david@fromorbit.com>

On Wed,  9 Jun 2010 10:37:18 +1000
Dave Chinner <david@fromorbit.com> wrote:

> From: Dave Chinner <dchinner@redhat.com>
> 
> 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
> 
> This has adverse effects on filesystem writeback behaviour. write_cache_pages()
> needs to terminate after a certain number of pages are written, not after a
> certain number of calls to ->writepage are made.  This is a regression
> introduced by 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 ("vfs: Add
> no_nrwrite_index_update writeback control flag"), but cannot be reverted
> directly due to subsequent bug fixes that have gone in on top of it.

Might be needed in -stable.  Unfortunately the most important piece of
information which is needed to make that decision was cunningly hidden
from us behind the vague-to-the-point-of-uselessness term "adverse
effects".

_what_ "adverse effects"??

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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: torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, xfs@oss.sgi.com, stable@kernel.org
Subject: Re: [PATCH 1/3] writeback: pay attention to wbc->nr_to_write in write_cache_pages
Date: Wed, 9 Jun 2010 14:09:42 -0700	[thread overview]
Message-ID: <20100609140942.6799c84a.akpm@linux-foundation.org> (raw)
In-Reply-To: <1276043840-1946-2-git-send-email-david@fromorbit.com>

On Wed,  9 Jun 2010 10:37:18 +1000
Dave Chinner <david@fromorbit.com> wrote:

> From: Dave Chinner <dchinner@redhat.com>
> 
> 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
> 
> This has adverse effects on filesystem writeback behaviour. write_cache_pages()
> needs to terminate after a certain number of pages are written, not after a
> certain number of calls to ->writepage are made.  This is a regression
> introduced by 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 ("vfs: Add
> no_nrwrite_index_update writeback control flag"), but cannot be reverted
> directly due to subsequent bug fixes that have gone in on top of it.

Might be needed in -stable.  Unfortunately the most important piece of
information which is needed to make that decision was cunningly hidden
from us behind the vague-to-the-point-of-uselessness term "adverse
effects".

_what_ "adverse effects"??


  reply	other threads:[~2010-06-09 21:07 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-06-09  0:37 [PATCH 0/3] writeback: bug fixes for 2.6.35 Dave Chinner
2010-06-09  0:37 ` Dave Chinner
2010-06-09  0:37 ` [PATCH 1/3] writeback: pay attention to wbc->nr_to_write in write_cache_pages Dave Chinner
2010-06-09  0:37   ` Dave Chinner
2010-06-09 21:09   ` Andrew Morton [this message]
2010-06-09 21:09     ` Andrew Morton
2010-06-09 22:58     ` Dave Chinner
2010-06-09 22:58       ` Dave Chinner
2010-06-10  0:08       ` Dave Chinner
2010-06-10  0:08         ` Dave Chinner
2010-06-23 20:36         ` [stable] " Greg KH
2010-06-23 20:36           ` Greg KH
2010-06-09  0:37 ` [PATCH 2/3] xfs: remove nr_to_write writeback windup Dave Chinner
2010-06-09  0:37   ` Dave Chinner
2010-06-09 21:10   ` Andrew Morton
2010-06-09 21:10     ` Andrew Morton
2010-06-09  0:37 ` [PATCH 3/3] writeback: limit write_cache_pages integrity scanning to current EOF Dave Chinner
2010-06-09  0:37   ` Dave Chinner
2010-06-09 21:12   ` Andrew Morton
2010-06-09 21:12     ` Andrew Morton

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