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 3/3] writeback: limit write_cache_pages integrity scanning to current EOF
Date: Wed, 9 Jun 2010 14:12:08 -0700 [thread overview]
Message-ID: <20100609141208.a1babcf4.akpm@linux-foundation.org> (raw)
In-Reply-To: <1276043840-1946-4-git-send-email-david@fromorbit.com>
On Wed, 9 Jun 2010 10:37:20 +1000
Dave Chinner <david@fromorbit.com> wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> 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.
>
> This patch will not prevent sync from blocking on large writes into
> holes. That requires more complex intervention while this patch only
> addresses the common append-case of this sync holdoff.
>
I don't know if this regression sucks enough to warrant backporting,
but the fix is simple and is independent of [1/3] and [2/3].
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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 3/3] writeback: limit write_cache_pages integrity scanning to current EOF
Date: Wed, 9 Jun 2010 14:12:08 -0700 [thread overview]
Message-ID: <20100609141208.a1babcf4.akpm@linux-foundation.org> (raw)
In-Reply-To: <1276043840-1946-4-git-send-email-david@fromorbit.com>
On Wed, 9 Jun 2010 10:37:20 +1000
Dave Chinner <david@fromorbit.com> wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> 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.
>
> This patch will not prevent sync from blocking on large writes into
> holes. That requires more complex intervention while this patch only
> addresses the common append-case of this sync holdoff.
>
I don't know if this regression sucks enough to warrant backporting,
but the fix is simple and is independent of [1/3] and [2/3].
next prev parent reply other threads:[~2010-06-09 21:10 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
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 [this message]
2010-06-09 21:12 ` Andrew Morton
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