From: tytso@mit.edu
To: Eric Sandeen <sandeen@redhat.com>
Cc: ext4 development <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH 3/3] ext4: don't use quota reservation for speculative metadata blocks
Date: Thu, 20 May 2010 19:10:41 -0400 [thread overview]
Message-ID: <20100520231041.GF16634@thunk.org> (raw)
In-Reply-To: <4BBCFF68.1060000@redhat.com>
On Wed, Apr 07, 2010 at 04:55:52PM -0500, Eric Sandeen wrote:
> Because we can badly over-reserve metadata when we
> calculate worst-case, it complicates things for quota, since
> we must reserve and then claim later, retry on EDQUOT, etc.
> Quota is also a generally smaller pool than fs free blocks,
> so this over-reservation hurts more, and more often.
>
> I'm of the opinion that it's not the worst thing to allow
> metadata to push a user slightly over quota. This simplifies
> the code and avoids the false quota rejections that result
> from worst-case speculation.
>
> This patch stops the speculative quota-charging for
> worst-case metadata requirements, and just charges quota
> when the blocks are allocated at writeout. It also is
> able to remove the try-again loop on EDQUOT.
>
> This patch has been tested indirectly by running the xfstests
> suite with a hack to mount & enable quota prior to the test.
>
> I also did a more specific test of fragmenting freespace
> and then doing a large delalloc write under quota; quota
> stopped me at the right amount of file IO, and then the
> writeout generated enough metadata (due to the fragmentation)
> that it put me slightly over quota, as expected.
>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Applied to the ext4 patch queue; there were slight adjustments to make
the patch apply.
Note: I did some testing of this patch, and found the following
warnings getting emitted when I ran fsstress:
fsstress -d /scratch/fsstress -n 100 -p 10
[ 93.338647] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 594944). There's a risk of filesystem corruption in case of system crash.
[ 93.390107] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 594944). There's a risk of filesystem corruption in case of system crash.
[ 149.249765] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 594142). There's a risk of filesystem corruption in case of system crash.
[ 149.305717] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 594142). There's a risk of filesystem corruption in case of system crash.
[ 152.523048] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 590048). There's a risk of filesystem corruption in case of system crash.
[ 152.544641] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 590048). There's a risk of filesystem corruption in case of system crash.
[ 154.147876] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 590049). There's a risk of filesystem corruption in case of system crash.
[ 154.192645] JBD: Spotted dirty metadata buffer (dev = sdc1, blocknr = 590049). There's a risk of filesystem corruption in case of system crash.
... but I found the same warning messages after I removed your patch,
so presumably this is a pre-existing condition with quotas and ext4.
Has anyone looked into this?
- Ted
next prev parent reply other threads:[~2010-05-20 23:10 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-07 21:45 [PATCH 0/3] ext4: don't use quota reservation for speculative metadata blocks Eric Sandeen
2010-04-07 21:49 ` [PATCH 1/3] quota: use flags interface for dquot alloc/free space Eric Sandeen
2010-04-12 13:22 ` Jan Kara
2010-05-20 22:29 ` tytso
2010-04-07 21:52 ` [PATCH 2/3] quota: add the option to not fail with EDQUOT in block allocation Eric Sandeen
2010-04-12 13:23 ` Jan Kara
2010-05-20 22:32 ` tytso
2010-04-07 21:55 ` [PATCH 3/3] ext4: don't use quota reservation for speculative metadata blocks Eric Sandeen
2010-04-12 13:36 ` Jan Kara
2010-05-20 23:10 ` tytso [this message]
2010-04-08 8:20 ` [PATCH 0/3] " Dmitry Monakhov
2010-04-08 15:28 ` Eric Sandeen
2010-04-11 9:37 ` Dmitry Monakhov
2010-04-12 13:15 ` Jan Kara
2010-04-12 13:22 ` Jan Kara
2010-04-12 13:40 ` Dmitry Monakhov
2010-04-12 13:33 ` Dmitry Monakhov
2010-04-12 13:37 ` Dmitry Monakhov
2010-04-12 13:42 ` tytso
2010-04-12 13:52 ` Dmitry Monakhov
2010-04-12 13:55 ` Jan Kara
2010-04-12 14:08 ` Dmitry Monakhov
2010-04-12 14:24 ` Jan Kara
2010-04-12 15:50 ` Eric Sandeen
2010-04-12 2:20 ` tytso
2010-04-12 14:03 ` Jan Kara
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