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Re: [PATCH] xfs: call xfs_idestroy_fork() in xfs_ilock() critical sectio

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs: call xfs_idestroy_fork() in xfs_ilock() critical section
From: Waiman Long <waiman.long@xxxxxx>
Date: Thu, 23 Apr 2015 13:14:40 -0400
Cc: xfs@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20150422231758.GQ21261@dastard>
References: <1429724021-7675-1-git-send-email-Waiman.Long@xxxxxx> <20150422231758.GQ21261@dastard>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130109 Thunderbird/10.0.12
On 04/22/2015 07:17 PM, Dave Chinner wrote:
--
Dave Chinner
david@xxxxxxxxxxxxx

xfs: xfs_attr_inactive leaves inconsistent attr fork state behind

From: Dave Chinner<dchinner@xxxxxxxxxx>

xfs_attr_inactive() is supposed to clean up the attribute fork when
the inode is being freed. While it removes attribute fork extents,
it completely ignores attributes in local format, which means that
there can still be active attributes on the inode after
xfs_attr_inactive() has run.

This leads to problems with concurrent inode writeback - the in-core
inode attribute fork is removed without locking on the assumption
that nothing will be attempting to access the attribute fork after a
call to xfs_attr_inactive() because it isn't supposed to exist on
disk any more.

To fix this, make xfs_attr_inactive() completely remove all traces
of the attribute fork from the inode, regardless of it's state.
Further, also remove the in-core attribute fork structure safely so
that there is nothing further that needs to be done by callers to
clean up the attribute fork. This means we can remove the in-core
and on-disk attribute forks atomically.

Also, on error simply remove the in-memory attribute fork. There's
nothing that can be done with it once we have failed to remove the
on-disk attribute fork, so we may as well just blow it away here
anyway.

cc:<stable@xxxxxxxxxxxxxxx>  # 3.12 to 4.0
Reported-by: Waiman Long<waiman.long@xxxxxx>
Signed-off-by: Dave Chinner<dchinner@xxxxxxxxxx>
---
  fs/xfs/libxfs/xfs_attr_leaf.c |  2 +-
  fs/xfs/libxfs/xfs_attr_leaf.h |  2 +-
  fs/xfs/xfs_attr_inactive.c    | 81 ++++++++++++++++++++++++++-----------------
  fs/xfs/xfs_inode.c            | 12 +++----
  4 files changed, 55 insertions(+), 42 deletions(-)

Thanks for figuring out a better way to fix the underlying problem. I tested it in my test machine and it did fix the errors that I had seen in my test case.

Tested-by: Waiman Long<Waiman.Long@xxxxxx>

Cheers,
Longman

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