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From: Mark Tinguely <tinguely@sgi.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 14/15] xfs: dquot log reservations are too small
Date: Thu, 27 Jun 2013 09:38:15 -0500	[thread overview]
Message-ID: <51CC4E57.1050305@sgi.com> (raw)
In-Reply-To: <1372313099-8121-15-git-send-email-david@fromorbit.com>

On 06/27/13 01:04, Dave Chinner wrote:
> From: Dave Chinner<dchinner@redhat.com>
>
> During review of the separate project quota inode patches, it bcame
> obvious that the dquot log reservation calculation underestimated
> the number dquots that can be modified in a transaction. This has
> it's roots way back in the Irix quota implementation.
>
> That is, when quotas were first implemented in XFS, it only
> supported user and project quotas as Irix did not have group quotas.
> Hence the worst case operation involving dquot modification was
> calculated to involve 2 user dquots and 1 project dquot or 1 user
> dequot and 2 project dquots. i.e. 3 dquots. This was determined back
> in 1996, and has remained unchanged ever since.
>
> However, back in 2001, the Linux XFS port dropped all support for
> project quota and implmented group quotas over the top. This was
> effectively done with a search-and-replace of project with group,
> and as such the log reservation was not changed. However, with the
> advent of group quotas, chmod and rename now could modify more than
> 3 dquots in a single transaction - both could modify 4 dquots. Hence
> this log reservation has been wrong for a long time.
>
> In 2005, project quotas were reintroduced into Linux, but they were
> implemented to be mutually exclusive to group quotas, and so this
> didn't add any new changes to the dquot log reservation. hence when
> project quotas were in use, everything was still fine, just like
> in the Irix days.
>
> Now, with the addition of the separate project quota inode, group
> and project quotas are no longer mutually exclusive, and hence
> operations can now modify three dquots per inode where previously it
> was only two. The worst case here is the rename transaction, which
> can allocate/free space on two different directory inodes, and if
> they have different uid/gid/prid configurations and are world
> writeable, then rename can actually modify 6 different dquots now.
>
> Further, the dquot log reservation doesn't take into account the
> space used by the dquot log format structure that preceeds the dquot
> that is logged, and hence further underestimates the worst case
> log space required by dquots during a transaction.
>
> Hence the worst case log reservation needs to be increased from 3 to
> 6, and it needs to take into account a log format header for each of
> those dquots.
>
> Signed-off-by: Dave Chinner<dchinner@redhat.com>
> ---

Looks good.

Reviewed-by: Mark Tinguely <tinguely@sgi.com>

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  reply	other threads:[~2013-06-27 14:38 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-27  6:04 [PATCH 00/15] xfs: patchset for 3.11 Dave Chinner
2013-06-27  6:04 ` [PATCH 01/15] xfs: update mount options documentation Dave Chinner
2013-06-27 14:48   ` Ben Myers
2013-06-27 19:08     ` Ben Myers
2013-06-28  2:09       ` Dave Chinner
2013-06-28  2:32         ` Dave Chinner
2013-06-28 15:39           ` Geoffrey Wehrman
2013-06-28 16:49             ` Eric Sandeen
2013-06-28 19:58               ` Geoffrey Wehrman
2013-06-28 17:27             ` Ric Wheeler
2013-06-28 19:39           ` Ben Myers
2013-06-29  2:38             ` Dave Chinner
2013-06-28  2:18       ` Eric Sandeen
2013-06-28 20:46         ` Ben Myers
2013-06-27  6:04 ` [PATCH 02/15] xfs: add pluging for bulkstat readahead Dave Chinner
2013-06-27  6:04 ` [PATCH 03/15] xfs: plug directory buffer readahead Dave Chinner
2013-06-27  6:04 ` [PATCH 04/15] xfs: don't use speculative prealloc for small files Dave Chinner
2013-06-27  6:04 ` [PATCH 05/15] xfs: don't do IO when creating an new inode Dave Chinner
2013-06-27  6:04 ` [PATCH 06/15] xfs: xfs_ifree doesn't need to modify the inode buffer Dave Chinner
2013-06-27  6:04 ` [PATCH 07/15] xfs: Introduce ordered log vector support Dave Chinner
2013-06-27  6:04 ` [PATCH 08/15] xfs: Introduce an ordered buffer item Dave Chinner
2013-06-27  6:04 ` [PATCH 09/15] xfs: Inode create log items Dave Chinner
2013-06-27  6:04 ` [PATCH 10/15] xfs: Inode create transaction reservations Dave Chinner
2013-06-27  6:04 ` [PATCH 11/15] xfs: Inode create item recovery Dave Chinner
2013-06-27  6:04 ` [PATCH 12/15] xfs: Use inode create transaction Dave Chinner
2013-06-27  6:04 ` [PATCH 13/15] xfs: remove local fork format handling from xfs_bmapi_write() Dave Chinner
2013-06-27  6:04 ` [PATCH 14/15] xfs: dquot log reservations are too small Dave Chinner
2013-06-27 14:38   ` Mark Tinguely [this message]
2013-06-28 17:18   ` Chandra Seetharaman
2013-06-29  2:42     ` Dave Chinner
2013-07-09 19:31       ` Ben Myers
2013-07-09 20:39         ` Dave Chinner
2013-07-09 20:42           ` Ben Myers
2013-06-27  6:04 ` [PATCH 15/15] xfs: implement inode change count Dave Chinner
2013-06-27 15:06   ` Mark Tinguely
2013-06-28 16:07   ` Chandra Seetharaman
2013-06-28 18:00   ` Ben Myers
2013-06-27 19:48 ` [PATCH 00/15] xfs: patchset for 3.11 Ben Myers

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