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From: Brian Foster <bfoster@redhat.com>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 1/2] xfs: setup VFS i_rwsem lockdep state correctly
Date: Thu, 7 Jun 2018 07:41:32 -0400	[thread overview]
Message-ID: <20180607114132.GA7798@bfoster> (raw)
In-Reply-To: <20180607053236.GR10363@dastard>

On Thu, Jun 07, 2018 at 03:32:36PM +1000, Dave Chinner wrote:
> On Thu, Jun 07, 2018 at 03:21:31PM +1000, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> > 
> > When lockdep is enabled, it changes the type of the inode i_rwsem
> > semaphore before unlocking a newly instantiated inode. THere is the
> > possibility that there is already a waiter on that inode lock by the
> > time we unlock the new inode, so having lockdep re-initialise the
> > lock is a vector for trouble.
> > 
> > Avoid this whole situation by setting up the i_rwsem lockdep class
> > at the same time we set up the XFS inode i_ilock classes and so the
> > VFS doesn't have to change the lock class itself when it is
> > potentially unsafe.
> > 
> > Signed-Off-By: Dave Chinner <dchinner@redhat.com>
> 
> I just realised that the VFS equivalent patch has made it upstream,
> too, which would help explain this a bit more. Darrick, can you add
> this to the commit message:
> 
> "This change is necessary because the equivalent fixes to the VFS
> code made in commit 1e2e547a93a0 ("do d_instantiate/unlock_new_inode
> combinations safely") are not relevant to XFS as it has it's own
> internal inode cache lookup and instantiation routines."
> 

The reference definitely helps, thanks. With that added:

Reviewed-by: Brian Foster <bfoster@redhat.com>

> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com
> --
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  reply	other threads:[~2018-06-07 11:41 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-07  5:21 [PATCH 0/2] xfs: fix a couple of potential deadlocks Dave Chinner
2018-06-07  5:21 ` [PATCH 1/2] xfs: setup VFS i_rwsem lockdep state correctly Dave Chinner
2018-06-07  5:32   ` Dave Chinner
2018-06-07 11:41     ` Brian Foster [this message]
2018-06-07  5:50   ` Allison Henderson
2018-06-07 14:53   ` Darrick J. Wong
2018-06-07  5:21 ` [PATCH 2/2] xfs: xfs_reflink_convert_cow() memory allocation deadlock Dave Chinner
2018-06-07  5:56   ` Allison Henderson
2018-06-07 14:46     ` Darrick J. Wong
2018-06-07 22:08       ` Dave Chinner
2018-06-07 11:41   ` Brian Foster
2018-06-07 14:48     ` Darrick J. Wong
2018-06-08  0:48     ` Dave Chinner

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