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Re: XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)

To: Ben Myers <bpm@xxxxxxx>
Subject: Re: XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 12 Dec 2013 10:53:35 +1100
Cc: Emmanuel Lacour <elacour@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20131211202226.GH1935@xxxxxxx>
References: <20131128091322.GC5337@xxxxxxxxxxxxxxx> <20131128100521.GO10988@dastard> <20131203095357.GC5405@xxxxxxxxxxxxxxx> <20131203125057.GU10988@dastard> <20131211202226.GH1935@xxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Dec 11, 2013 at 02:22:26PM -0600, Ben Myers wrote:
> On Tue, Dec 03, 2013 at 11:50:57PM +1100, Dave Chinner wrote:
> > On Tue, Dec 03, 2013 at 10:53:58AM +0100, Emmanuel Lacour wrote:
> > > On Thu, Nov 28, 2013 at 09:05:21PM +1100, Dave Chinner wrote:
> > > > On Thu, Nov 28, 2013 at 10:13:22AM +0100, Emmanuel Lacour wrote:
> > > > > 
> > > > > Dear XFS users,
> > > > > 
> > > > > 
> > > > > I run a Ceph cluster using XFS on Debian wheezy servers and Linux 3.10
> > > > > (debian backports). I see the following line in our logs:
> > > > > 
> > > > > XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)
> > > > > 
> > > > > does this reveal a problem in my setup or may I ignore it? If it's a
> > > > > problem, can someone give me any hint on solving this?
> > > > 
> > > > It might be, but you need to provide more information for us to be
> > > > able to make any intelligent comment on the message. Start here:
> > > > 
> > > > http://xfs.org/index.php/XFS_FAQ#Q:_What_information_should_I_include_when_reporting_a_problem.3F
> > > > 
> > > 
> > > 
> > > The problem continue and crashed my ceph cluster again, so here is all
> > > the informations said in the FAQ:
> > > 
> > > http://people.easter-eggs.org/~manu/xfs.log
> > 
> > OK, 32GB RAM, no obvious shortage, no dirty or writeback data.
> > 2TB SATA drives, 32AGs, only unusual setting is 64k directory block
> > size.
> > 
> > Yup, there's your problem:
> > 
> > [4583991.478469] ceph-osd        D ffff88047fc93f40     0 22951
> > 1 0x00000004
> > [4583991.478471]  ffff88046d241140 0000000000000082 ffffffff81047e75
> > ffff88046f949800
> > [4583991.478475]  0000000000013f40 ffff88039eb0bfd8 ffff88039eb0bfd8
> > ffff88046d241140
> > [4583991.478479]  0000000000000000 00000001444d68bd ffff88046d241140
> > 0000000000000005
> > [4583991.478483] Call Trace:
> > [4583991.478487]  [<ffffffff81047e75>] ? internal_add_timer+0xd/0x28
> > [4583991.478491]  [<ffffffff8138e34a>] ? schedule_timeout+0xeb/0x123
> > [4583991.478494]  [<ffffffff81047e63>] ? 
> > ftrace_raw_event_timer_class+0x9d/0x9d
> > [4583991.478498]  [<ffffffff8138edb6>] ? io_schedule_timeout+0x60/0x86
> > [4583991.478502]  [<ffffffff810d85ad>] ? congestion_wait+0x70/0xdb
> > [4583991.478505]  [<ffffffff8105858f>] ? abort_exclusive_wait+0x79/0x79
> > [4583991.478518]  [<ffffffffa056e3f9>] ? kmem_alloc+0x65/0x6f [xfs]
> > [4583991.478535]  [<ffffffffa0592c4a>] ? xfs_dir2_block_to_sf+0x5b/0x1fb 
> > [xfs]
> > [4583991.478550]  [<ffffffffa0592be0>] ? xfs_dir2_block_sfsize+0x15b/0x16a 
> > [xfs]
> > [4583991.478566]  [<ffffffffa058bf9a>] ? 
> > xfs_dir2_block_removename+0x1c7/0x208 [xfs]
> > [4583991.478581]  [<ffffffffa058ab4a>] ? xfs_dir_removename+0xda/0x114 [xfs]
> > [4583991.478594]  [<ffffffffa056a55c>] ? xfs_rename+0x428/0x554 [xfs]
> > [4583991.478606]  [<ffffffffa0567321>] ? xfs_vn_rename+0x5e/0x65 [xfs]
> > [4583991.478610]  [<ffffffff8111677b>] ? vfs_rename+0x224/0x35f
> > [4583991.478614]  [<ffffffff81113d0b>] ? lookup_dcache+0x22/0x95
> > [4583991.478618]  [<ffffffff81116a7e>] ? SYSC_renameat+0x1c8/0x257
> > [4583991.478622]  [<ffffffff810fb0fd>] ? __cache_free.isra.45+0x178/0x187
> > [4583991.478625]  [<ffffffff81117eb1>] ? SyS_mkdirat+0x2e/0xce
> > [4583991.478629]  [<ffffffff8100d56a>] ? do_notify_resume+0x53/0x68
> > [4583991.478633]  [<ffffffff81395429>] ?  system_call_fastpath+0x16/0x1b
> > 
> > It'll be stuck on this:
> > 
> >     hdr = kmem_alloc(mp->m_dirblksize, KM_SLEEP);
> > 
> > which is trying to allocate a contiguous 64k buffer to copy the
> > direct contents into before freeing the block and then formatting
> > them into the inode. The failure will be caused by memory
> > fragmentation, and the only way around it is to avoid the contiguous
> > allocation of that size.
> > 
> > Which, I think, is pretty easy to do. Yup, barely smoke tested patch
> > below that demonstrates the fix. Beware - patch may eat babies and
> > ask for more. Use it at your own risk!
> > 
> > I'll post it for review once it's had some testing and I know it
> > doesn't corrupt directories all over the place.
> > 
> > > This may be related to a friend problem here:
> > > 
> > > http://tracker.ceph.com/issues/6386
> > 
> > Doesn't look related, unless the OOM killer is being triggered
> > somehow...
> > 
> > Hmmmm - there's also a good chance the the transaction commit code
> > has this same problem contiguous allocation problem given that it
> > has to allocate enough space to log an entire directory buffer. Good
> > guess - there's another thread stuck on exactly that:
> > 
> > [4583991.476833] ceph-osd        D ffff88047fc33f40     0 11072 1 0x00000004
> > [4583991.476836]  ffff88038b32a040 0000000000000082 ffffffff81047e75 
> > ffff88046f946040
> > [4583991.476840]  0000000000013f40 ffff88048ea11fd8 ffff88048ea11fd8 
> > ffff88038b32a040
> > [4583991.476844]  0000000000000000 00000001444d68be ffff88038b32a040 
> > 0000000000000005
> > [4583991.476848] Call Trace:
> > [4583991.476852]  [<ffffffff81047e75>] ? internal_add_timer+0xd/0x28
> > [4583991.476855]  [<ffffffff8138e34a>] ? schedule_timeout+0xeb/0x123
> > [4583991.476859]  [<ffffffff81047e63>] ? 
> > ftrace_raw_event_timer_class+0x9d/0x9d
> > [4583991.476862]  [<ffffffff8138edb6>] ? io_schedule_timeout+0x60/0x86
> > [4583991.476867]  [<ffffffff810d85ad>] ? congestion_wait+0x70/0xdb
> > [4583991.476870]  [<ffffffff8105858f>] ? abort_exclusive_wait+0x79/0x79
> > [4583991.476883]  [<ffffffffa056e3f9>] ? kmem_alloc+0x65/0x6f [xfs]
> > [4583991.476899]  [<ffffffffa05a77a6>] ? xfs_log_commit_cil+0xe8/0x3d1 [xfs]
> > [4583991.476904]  [<ffffffff810748ab>] ? current_kernel_time+0x9/0x30
> > [4583991.476909]  [<ffffffff81041942>] ? current_fs_time+0x27/0x2d
> > [4583991.476925]  [<ffffffffa05a3b7b>] ? xfs_trans_commit+0x62/0x1cf [xfs]
> > [4583991.476939]  [<ffffffffa056d3ad>] ? xfs_create+0x41e/0x54f [xfs]
> > [4583991.476943]  [<ffffffff81114574>] ? lookup_fast+0x3d/0x215
> > [4583991.476954]  [<ffffffffa056cf29>] ? xfs_lookup+0x88/0xee [xfs]
> > [4583991.476966]  [<ffffffffa0567428>] ? xfs_vn_mknod+0xb7/0x162 [xfs]
> > [4583991.476970]  [<ffffffff81115fda>] ? vfs_create+0x62/0x8b
> > [4583991.476974]  [<ffffffff81113d0b>] ? lookup_dcache+0x22/0x95
> > [4583991.476978]  [<ffffffff81117179>] ? do_last+0x595/0xa16
> > [4583991.476982]  [<ffffffff811176be>] ? path_openat+0xc4/0x335
> > [4583991.476985]  [<ffffffff81117bda>] ? do_filp_open+0x2a/0x6e
> > [4583991.476989]  [<ffffffff81120b62>] ? __alloc_fd+0xd0/0xe1
> > [4583991.476993]  [<ffffffff8110b684>] ? do_sys_open+0x5c/0xe0
> > [4583991.476996]  [<ffffffff81395429>] ? system_call_fastpath+0x16/0x1b
> > 
> > That one isn't so easy to fix, unfortunately.
> > 
> > Cheers,
> > 
> > Dave.
> > -- 
> > Dave Chinner
> > david@xxxxxxxxxxxxx
> > 
> > xfs: xfs_dir2_block_to_sf temp buffer allocation fails 
> > 
> > From: Dave Chinner <dchinner@xxxxxxxxxx>
> > 
> > If we are using a large directory block size, and memory becomes
> > fragmented, we can get memory allocation failures trying to
> > kmem_alloc(64k) for a temporary buffer. However, there is not need
> > for a directory buffer sized allocation, as the end result ends up
> > in the inode literal area. This is, at most, slightly less than 2k
> > of space, and hence we don't need an allocation larger than that
> > fora temporary buffer.
> > 
> > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> D'oh, I missed this one too.  If you stick 'patch' in the subject they'll have
> additional visibility.
> 
> Looks good to me.
> 
> Reviewed-by: Ben Myers <bpm@xxxxxxx>

When I reply in line like this it's more of a case of "please test
this patch to see if it fixes your problem" question, not really an
official posting of a patch because it's very likely I have just
written the patch and have only done a 5 minute smoke test of the
patch. So in this context, it's not really a "please review and
commit" request.

The issue is that I haven't reposted the patch in a separate series
asking for reviews and commit as I normally do after I've tested it
properly and are happy with it.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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