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From: Dave Chinner <david@fromorbit.com>
To: Brian Foster <bfoster@redhat.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 3/9] repair: ensure prefetched buffers have CRCs validated
Date: Wed, 16 Apr 2014 10:41:45 +1000	[thread overview]
Message-ID: <20140416004145.GB15995@dastard> (raw)
In-Reply-To: <20140415220559.GE3470@laptop.bfoster>

On Tue, Apr 15, 2014 at 06:06:00PM -0400, Brian Foster wrote:
> On Wed, Apr 16, 2014 at 07:46:42AM +1000, Dave Chinner wrote:
> > On Tue, Apr 15, 2014 at 03:40:00PM -0400, Brian Foster wrote:
> > > Should we always expect an unchecked buffer to be read with an ops
> > > vector before being written? Even if so, this might look cleaner if we
> > > didn't encode the possibility of running a read verifier on a dirty
> > > buffer. I presume that would always fail as the crc is updated in the
> > > write verifier.
> > 
> > It should fail, and that's a good thing because writing to an
> > unchecked buffer would indicate that we didn't validate it properly
> > in the first place. Hence I thought that doing it this way leaves
> > a canary that traps other problem usage with unchecked buffers.
> > 
> > Realistically, we shouldn't be writing unchecked buffers - prefetch
> > doesn't touch buffers, it just does IO, and so someone else has to
> > read the buffers before they can be dirtied. If it's read without an
> > ops structure then modified and read again with an ops structure,
> > we'll catch it...
> > 
> 
> Ah, I see. That sounds good, but a small comment there with the
> reasoning to allow a read verifier to run on a dirty buffer would be
> nice. :)

Ok, I'll add one.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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  reply	other threads:[~2014-04-16  0:42 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-04-15  8:24 [PATCH 0/9] xfs_db, xfs_repair: improve CRC error detection Dave Chinner
2014-04-15  8:24 ` [PATCH 1/9] db: don't claim unchecked CRCs are correct Dave Chinner
2014-04-21  7:00   ` Christoph Hellwig
2014-04-21 23:13     ` Dave Chinner
2014-04-15  8:24 ` [PATCH 2/9] db: verify buffer on type change Dave Chinner
2014-04-21  7:02   ` Christoph Hellwig
2014-04-21 23:14     ` Dave Chinner
2014-04-15  8:24 ` [PATCH 3/9] repair: ensure prefetched buffers have CRCs validated Dave Chinner
2014-04-15 19:40   ` Brian Foster
2014-04-15 21:46     ` Dave Chinner
2014-04-15 22:06       ` Brian Foster
2014-04-16  0:41         ` Dave Chinner [this message]
2014-04-15  8:24 ` [PATCH 4/9] repair: detect and correct CRC errors in directory blocks Dave Chinner
2014-04-21  7:08   ` Christoph Hellwig
2014-04-15  8:24 ` [PATCH 5/9] repair: detect CRC errors in AG headers Dave Chinner
2014-04-15 19:40   ` Brian Foster
2014-04-15 21:52     ` Dave Chinner
2014-04-21  7:11   ` Christoph Hellwig
2014-04-21 23:35     ` Dave Chinner
2014-04-22  6:47       ` Christoph Hellwig
2014-04-22  9:10         ` Dave Chinner
2014-04-22  9:41           ` Christoph Hellwig
2014-04-15  8:24 ` [PATCH 6/9] repair: report AG btree verifier errors Dave Chinner
2014-04-15 19:40   ` Brian Foster
2014-04-15 21:53     ` Dave Chinner
2014-04-15  8:24 ` [PATCH 7/9] repair: remove more dirv1 leftovers Dave Chinner
2014-04-16 13:23   ` Brian Foster
2014-04-21  7:14     ` Christoph Hellwig
2014-04-21  7:13   ` Christoph Hellwig
2014-04-15  8:25 ` [PATCH 8/9] repair: handle remote sylmlink CRC errors Dave Chinner
2014-04-16 13:23   ` Brian Foster
2014-04-15  8:25 ` [PATCH 9/9] repair: detect and handle attribute tree " Dave Chinner
2014-04-16 13:25   ` Brian Foster
2014-04-21 23:27     ` Dave Chinner
  -- strict thread matches above, loose matches on Subject: below --
2014-04-24  5:01 [PATCH 0/9 V2] xfs_db, xfs_repair: improve CRC error detection Dave Chinner
2014-04-24  5:01 ` [PATCH 3/9] repair: ensure prefetched buffers have CRCs validated Dave Chinner
2014-04-25  5:47   ` Christoph Hellwig
2014-04-28 21:04 [PATCH 0/9 v3] xfs_db, xfs_repair: improve CRC error detection Dave Chinner
2014-04-28 21:04 ` [PATCH 3/9] repair: ensure prefetched buffers have CRCs validated Dave Chinner
2014-04-29 14:05   ` Brian Foster
2014-04-29 18:15   ` Christoph Hellwig

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