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From: Jamie Lokier <jamie@shareable.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	xfs@oss.sgi.com
Subject: Re: [PATCH 5/4] writeback: limit write_cache_pages integrity scanning to current EOF
Date: Wed, 21 Apr 2010 00:28:19 +0100	[thread overview]
Message-ID: <20100420232819.GR11723@shareable.org> (raw)
In-Reply-To: <20100420034005.GA15130@dastard>

Dave Chinner wrote:
> sync can currently take a really long time if a concurrent writer is
> extending a file. The problem is that the dirty pages on the address
> space grow in the same direction as write_cache_pages scans, so if
> the writer keeps ahead of writeback, the writeback will not
> terminate until the writer stops adding dirty pages.
> 
> For a data integrity sync, we only need to write the pages dirty at
> the time we start the writeback, so we can stop scanning once we get
> to the page that was at the end of the file at the time the scan
> started.
> 
> This will prevent operations like copying a large file preventing
> sync from completing as it will not write back pages that were
> dirtied after the sync was started. This does not impact the
> existing integrity guarantees, as any dirty page (old or new)
> within the EOF range at the start of the scan will still be
> captured.

I guess it can still get stuck if someone does ftruncate() first, then
writes to the hole?

-- Jamie

WARNING: multiple messages have this Message-ID (diff)
From: Jamie Lokier <jamie@shareable.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	xfs@oss.sgi.com
Subject: Re: [PATCH 5/4] writeback: limit write_cache_pages integrity scanning to current EOF
Date: Wed, 21 Apr 2010 00:28:19 +0100	[thread overview]
Message-ID: <20100420232819.GR11723@shareable.org> (raw)
In-Reply-To: <20100420034005.GA15130@dastard>

Dave Chinner wrote:
> sync can currently take a really long time if a concurrent writer is
> extending a file. The problem is that the dirty pages on the address
> space grow in the same direction as write_cache_pages scans, so if
> the writer keeps ahead of writeback, the writeback will not
> terminate until the writer stops adding dirty pages.
> 
> For a data integrity sync, we only need to write the pages dirty at
> the time we start the writeback, so we can stop scanning once we get
> to the page that was at the end of the file at the time the scan
> started.
> 
> This will prevent operations like copying a large file preventing
> sync from completing as it will not write back pages that were
> dirtied after the sync was started. This does not impact the
> existing integrity guarantees, as any dirty page (old or new)
> within the EOF range at the start of the scan will still be
> captured.

I guess it can still get stuck if someone does ftruncate() first, then
writes to the hole?

-- Jamie

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  reply	other threads:[~2010-04-20 23:28 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
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 [this message]
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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