From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 3/8] xfs: make the log ticket transaction id random
Date: Sat, 3 Apr 2010 05:31:56 -0400 [thread overview]
Message-ID: <20100403093156.GD20166@infradead.org> (raw)
In-Reply-To: <1270125691-29266-4-git-send-email-david@fromorbit.com>
On Thu, Apr 01, 2010 at 11:41:26PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> The transaction ID that is written to the log for a transaction is
> currently set by taking the lower 32 bits of the memory address of
> the ticket structure. This is not guaranteed to be unique as
> tickets comes from a slab and slots can be reallocated immediately
> after being freed. As a result, there is no guarantee of uniqueness
> in the ticket ID value.
>
> Fix this by assigning a random number to the ticket ID field so that
> it is extremely unlikely that duplicates will occur and remove the
> possibility of transactions being mixed up during recovery due to
> duplicate IDs.
I already noticed that you uses a random tid in your delayed logging
patches. But even a random number means we can get duplicate tids.
If we assign tids from a wrapping counter instead we can guarantee
that they are unique as long as we don't have more than UINT_MAX
transactions in the log, which is a limitation we could easily enforce.
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next prev parent reply other threads:[~2010-04-03 9:30 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-01 12:41 [PATCH 0/8] xfs: bug fixes, cleanups and tracing Dave Chinner
2010-04-01 12:41 ` [PATCH 2/8] xfs: don't warn on EAGAIN in inode reclaim Dave Chinner
2010-04-03 9:25 ` Christoph Hellwig
2010-04-01 12:41 ` [PATCH 3/8] xfs: make the log ticket transaction id random Dave Chinner
2010-04-03 9:31 ` Christoph Hellwig [this message]
2010-04-05 23:39 ` Dave Chinner
2010-04-13 18:12 ` Christoph Hellwig
2010-04-01 12:41 ` [PATCH 4/8] xfs: add log item recovery tracing Dave Chinner
2010-04-03 9:36 ` Christoph Hellwig
2010-04-05 23:40 ` Dave Chinner
2010-04-01 12:41 ` [PATCH 5/8] xfs: convert the per-mount dquot list to use list heads Dave Chinner
2010-04-03 9:59 ` Christoph Hellwig
2010-04-01 12:41 ` [PATCH 6/8] xfs: remove duplicate code from dquot reclaim Dave Chinner
2010-04-03 10:00 ` Christoph Hellwig
2010-04-01 12:41 ` [PATCH 7/8] xfs: convert the dquot hash list to use list heads Dave Chinner
2010-04-03 10:00 ` Christoph Hellwig
2010-04-01 12:41 ` [PATCH 8/8] xfs: convert the dquot free " Dave Chinner
2010-04-03 10:00 ` Christoph Hellwig
2010-04-03 10:02 ` [PATCH 9/8] xfs: remove xfs_dqmarker Christoph Hellwig
2010-04-05 23:20 ` Dave Chinner
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