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From: tytso@mit.edu
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com,
	"Aneesh Kumar K. V" <aneesh.kumar@linux.vnet.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] writeback: pay attention to wbc->nr_to_write in write_cache_pages
Date: Sat, 1 May 2010 15:47:10 -0400	[thread overview]
Message-ID: <20100501194710.GV14986@thunk.org> (raw)
In-Reply-To: <20100430124329.10a4c02b.akpm@linux-foundation.org>

On Fri, Apr 30, 2010 at 12:43:29PM -0700, Andrew Morton wrote:
> 
> Maybe that fs shouldn't be calling write_cache_pages() at all.  After
> all, write_cache_pages() is a wrapper which emits a sequence of calls
> to ->writepage(), and ->writepage() writes a page.

On my todo list is to fix ext4 to not call write_cache_pages() at all.
We are seriously abusing that function ATM, since we're not actually
writing the pages when we call write_cache_pages().  I won't go into
what we're doing, because it's too embarassing, but suffice it to say
that we end up calling pagevec_lookup() or pagevec_lookup_tag()
*four*, count them *four* times while trying to do writeback.

I have a simple patch that gives ext4 our own copy of
write_cache_pages(), and then simplifies it a lot, and fixes a bunch
of problems, but then I discarded it in favor of fundamentally redoing
how we do writeback at all, but it's going to take a while to get
things completely right.  But I am working to try to fix this.

If it would help, I can ressurect the "fork write_cache_pages() and
simplify" patch, so ext4 isn't dependent on the mm/page-writeback.c's
write_cache_pages(), if there is an immediate, short-term need to fix
that function.

						- Ted

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WARNING: multiple messages have this Message-ID (diff)
From: tytso@mit.edu
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Aneesh Kumar K. V" <aneesh.kumar@linux.vnet.ibm.com>,
	Dave Chinner <david@fromorbit.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	xfs@oss.sgi.com
Subject: Re: [PATCH 3/4] writeback: pay attention to wbc->nr_to_write in write_cache_pages
Date: Sat, 1 May 2010 15:47:10 -0400	[thread overview]
Message-ID: <20100501194710.GV14986@thunk.org> (raw)
In-Reply-To: <20100430124329.10a4c02b.akpm@linux-foundation.org>

On Fri, Apr 30, 2010 at 12:43:29PM -0700, Andrew Morton wrote:
> 
> Maybe that fs shouldn't be calling write_cache_pages() at all.  After
> all, write_cache_pages() is a wrapper which emits a sequence of calls
> to ->writepage(), and ->writepage() writes a page.

On my todo list is to fix ext4 to not call write_cache_pages() at all.
We are seriously abusing that function ATM, since we're not actually
writing the pages when we call write_cache_pages().  I won't go into
what we're doing, because it's too embarassing, but suffice it to say
that we end up calling pagevec_lookup() or pagevec_lookup_tag()
*four*, count them *four* times while trying to do writeback.

I have a simple patch that gives ext4 our own copy of
write_cache_pages(), and then simplifies it a lot, and fixes a bunch
of problems, but then I discarded it in favor of fundamentally redoing
how we do writeback at all, but it's going to take a while to get
things completely right.  But I am working to try to fix this.

If it would help, I can ressurect the "fork write_cache_pages() and
simplify" patch, so ext4 isn't dependent on the mm/page-writeback.c's
write_cache_pages(), if there is an immediate, short-term need to fix
that function.

						- Ted

  reply	other threads:[~2010-05-01 19:45 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
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 [this message]
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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