From: Mark Tinguely <tinguely@sgi.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 06/18] xfs: fix buffer lookup race on allocation failure
Date: Fri, 13 Apr 2012 13:32:27 -0500 [thread overview]
Message-ID: <4F88713B.7070805@sgi.com> (raw)
In-Reply-To: <1334319061-12968-7-git-send-email-david@fromorbit.com>
On 04/13/12 07:10, Dave Chinner wrote:
> From: Dave Chinner<dchinner@redhat.com>
>
> When memory allocation fails to add the page array or tht epages to
> a buffer during xfs_buf_get(), the buffer is left in the cache in a
> partially initialised state. There is enough state left for the next
> lookup on that buffer to find the buffer, and for the buffer to then
> be used without finishing the initialisation. As a result, when an
> attempt to do IO on the buffer occurs, it fails with EIO because
> there are no pages attached to the buffer.
>
> We cannot remove the buffer from the cache immediately and free it,
> because there may already be a racing lookup that is blocked on the
> buffer lock. Hence the moment we unlock the buffer to then free it,
> the other user is woken and we have a use-after-free situation.
>
> To avoid this race condition altogether, allocate the pages for the
> buffer before we insert it into the cache. This then means that we
> don't have an allocation failure case to deal after the buffer is
> already present in the cache, and hence avoid the problem
> altogether. In most cases we won't have racing inserts for the same
> buffer, and so won't increase the memory pressure allocation before
> insertion may entail.
>
> Signed-off-by: Dave Chinner<dchinner@redhat.com>
> ---
Much simpler idea than v1. Looks good.
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
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next prev parent reply other threads:[~2012-04-13 18:32 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-13 12:10 [PATCH 0/18] xfs: current patch queue Dave Chinner
2012-04-13 12:10 ` [PATCH 01/18] xfs: Ensure inode reclaim can run during quotacheck Dave Chinner
2012-04-13 18:01 ` Mark Tinguely
2012-04-29 21:37 ` Christoph Hellwig
2012-04-13 12:10 ` [PATCH 02/18] xfs: pass shutdown method into xfs_trans_ail_delete_bulk Dave Chinner
2012-04-13 17:40 ` Mark Tinguely
2012-04-13 23:04 ` Dave Chinner
2012-04-13 23:38 ` [PATCH 02/18 V2] " Dave Chinner
2012-04-16 18:49 ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 03/18] xfs: Do background CIL flushes via a workqueue Dave Chinner
2012-04-17 17:54 ` Mark Tinguely
2012-04-17 21:21 ` Ben Myers
2012-04-17 21:49 ` Ben Myers
2012-04-18 1:47 ` Dave Chinner
2012-04-30 1:24 ` Dave Chinner
2012-04-30 6:09 ` Dave Chinner
2012-04-18 1:58 ` Dave Chinner
2012-04-13 12:10 ` [PATCH 04/18] xfs: page type check in writeback only checks last buffer Dave Chinner
2012-04-16 16:15 ` Mark Tinguely
2012-04-29 21:39 ` Christoph Hellwig
2012-04-30 0:29 ` Dave Chinner
2012-04-13 12:10 ` [PATCH 05/18] xfs: Use preallocation for inodes with extsz hints Dave Chinner
2012-04-13 16:45 ` Mark Tinguely
2012-04-16 15:59 ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 06/18] xfs: fix buffer lookup race on allocation failure Dave Chinner
2012-04-13 18:32 ` Mark Tinguely [this message]
2012-04-13 12:10 ` [PATCH 07/18] xfs: check for buffer errors before waiting Dave Chinner
2012-04-13 17:56 ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 08/18] xfs: fix incorrect b_offset initialisation Dave Chinner
2012-04-13 12:10 ` [PATCH 09/18] xfs: use kmem_zone_zalloc for buffers Dave Chinner
2012-04-13 12:10 ` [PATCH 10/18] xfs: clean up buffer get/read call API Dave Chinner
2012-04-13 12:10 ` [PATCH 11/18] xfs: kill b_file_offset Dave Chinner
2012-04-13 12:10 ` [PATCH 12/18] xfs: use blocks for counting length of buffers Dave Chinner
2012-04-13 12:10 ` [PATCH 13/18] xfs: use blocks for storing the desired IO size Dave Chinner
2012-04-13 12:10 ` [PATCH 14/18] xfs: kill xfs_buf_btoc Dave Chinner
2012-04-13 12:10 ` [PATCH 15/18] xfs: kill XBF_LOCK Dave Chinner
2012-04-13 21:20 ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 16/18] xfs: kill xfs_read_buf() Dave Chinner
2012-04-13 12:11 ` [PATCH 17/18] xfs: kill XBF_DONTBLOCK Dave Chinner
2012-04-16 14:34 ` Mark Tinguely
2012-04-13 12:11 ` [PATCH 18/18] xfs: use iolock on XFS_IOC_ALLOCSP calls Dave Chinner
2012-04-16 15:10 ` Mark Tinguely
2012-04-16 21:29 ` [PATCH 0/18] xfs: current patch queue Ben Myers
2012-04-17 4:12 ` Dave Chinner
2012-04-17 14:44 ` Ben Myers
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