From: Dave Chinner <david@fromorbit.com>
To: NeilBrown <neilb@suse.de>
Cc: linux-mm@kvack.org, linux-nfs@vger.kernel.org,
linux-kernel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [PATCH 16/19] VFS: use GFP_NOFS rather than GFP_KERNEL in __d_alloc.
Date: Wed, 16 Apr 2014 16:25:20 +1000 [thread overview]
Message-ID: <20140416062520.GG15995@dastard> (raw)
In-Reply-To: <20140416040337.10604.61837.stgit@notabene.brown>
On Wed, Apr 16, 2014 at 02:03:37PM +1000, NeilBrown wrote:
> __d_alloc can be called with i_mutex held, so it is safer to
> use GFP_NOFS.
>
> lockdep reports this can deadlock when loop-back NFS is in use,
> as nfsd may be required to write out for reclaim, and nfsd certainly
> takes i_mutex.
But not the same i_mutex as is currently held. To me, this seems
like a false positive? If you are holding the i_mutex on an inode,
then you have a reference to the inode and hence memory reclaim
won't ever take the i_mutex on that inode.
FWIW, this sort of false positive was a long stabding problem for
XFS - we managed to get rid of most of the false positives like this
by ensuring that only the ilock is taken within memory reclaim and
memory reclaim can't be entered while we hold the ilock.
You can't do that with the i_mutex, though....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2014-04-16 6:25 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-16 4:03 [PATCH/RFC 00/19] Support loop-back NFS mounts NeilBrown
2014-04-16 4:03 ` [PATCH 06/19] nfsd: set PF_FSTRANS for nfsd threads NeilBrown
2014-04-16 7:28 ` Peter Zijlstra
2014-04-16 4:03 ` [PATCH 03/19] lockdep: improve scenario messages for RECLAIM_FS errors NeilBrown
2014-04-16 7:22 ` Peter Zijlstra
2014-04-16 4:03 ` [PATCH 08/19] Set PF_FSTRANS while write_cache_pages calls ->writepage NeilBrown
2014-04-16 4:03 ` [PATCH 05/19] SUNRPC: track whether a request is coming from a loop-back interface NeilBrown
2014-04-16 14:47 ` Jeff Layton
2014-04-16 23:25 ` NeilBrown
2014-04-16 4:03 ` [PATCH 04/19] Make effect of PF_FSTRANS to disable __GFP_FS universal NeilBrown
2014-04-16 5:37 ` Dave Chinner
2014-04-16 6:17 ` NeilBrown
2014-04-17 1:03 ` NeilBrown
2014-04-17 4:41 ` Dave Chinner
2014-04-16 4:03 ` [PATCH 01/19] Promote current_{set, restore}_flags_nested from xfs to global NeilBrown
2014-04-16 4:03 ` [PATCH 12/19] NET: set PF_FSTRANS while holding rtnl_lock NeilBrown
2014-04-16 4:03 ` [PATCH 10/19] NET: set PF_FSTRANS while holding sk_lock NeilBrown
2014-04-16 5:13 ` Eric Dumazet
2014-04-16 5:47 ` NeilBrown
2014-04-16 13:00 ` David Miller
2014-04-17 2:38 ` NeilBrown
2014-04-16 4:03 ` [PATCH 11/19] FS: set PF_FSTRANS while holding mmap_sem in exec.c NeilBrown
2014-04-16 4:03 ` [PATCH 14/19] driver core: set PF_FSTRANS while holding gdp_mutex NeilBrown
2014-04-16 4:03 ` [PATCH 07/19] nfsd and VM: use PF_LESS_THROTTLE to avoid throttle in shrink_inactive_list NeilBrown
2014-04-16 4:03 ` [PATCH 09/19] XFS: ensure xfs_file_*_read cannot deadlock in memory allocation NeilBrown
2014-04-16 6:04 ` Dave Chinner
2014-04-16 6:27 ` NeilBrown
2014-04-16 6:31 ` Dave Chinner
2014-04-16 4:03 ` [PATCH 02/19] lockdep: lockdep_set_current_reclaim_state should save old value NeilBrown
2014-04-16 4:03 ` [PATCH 13/19] MM: set PF_FSTRANS while allocating per-cpu memory to avoid deadlock NeilBrown
2014-04-16 5:49 ` Dave Chinner
2014-04-16 6:22 ` NeilBrown
2014-04-16 6:30 ` Dave Chinner
2014-04-16 4:03 ` [PATCH 17/19] VFS: set PF_FSTRANS while namespace_sem is held NeilBrown
2014-04-16 4:46 ` Al Viro
2014-04-16 5:52 ` NeilBrown
[not found] ` <20140416155230.4d02e4b9-wvvUuzkyo1EYVZTmpyfIwg@public.gmane.org>
2014-04-16 16:37 ` Al Viro
2014-04-16 4:03 ` [PATCH 19/19] XFS: set PF_FSTRANS while ilock is held in xfs_free_eofblocks NeilBrown
2014-04-16 6:18 ` Dave Chinner
2014-04-16 4:03 ` [PATCH 16/19] VFS: use GFP_NOFS rather than GFP_KERNEL in __d_alloc NeilBrown
2014-04-16 6:25 ` Dave Chinner [this message]
2014-04-16 6:49 ` NeilBrown
2014-04-16 9:00 ` Dave Chinner
2014-04-17 0:51 ` NeilBrown
2014-04-17 5:58 ` Dave Chinner
2014-04-16 4:03 ` [PATCH 18/19] nfsd: set PF_FSTRANS during nfsd4_do_callback_rpc NeilBrown
2014-04-16 4:03 ` [PATCH 15/19] nfsd: set PF_FSTRANS when client_mutex is held NeilBrown
2014-04-16 14:42 ` [PATCH/RFC 00/19] Support loop-back NFS mounts Jeff Layton
2014-04-17 0:20 ` NeilBrown
2014-04-17 1:27 ` Dave Chinner
2014-04-17 1:50 ` NeilBrown
2014-04-17 4:23 ` Dave Chinner
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