Re: [PATCH] pnfs: fix BUG in filelayout_recover_commit_reqs

[Trond Myklebust <trond.myklebust@primarydata.com>]

On Jan 22, 2014, at 7:19, Weston Andros Adamson <dros@primarydata.com> wrote:

> This might actually need a CC stable, although I’m not sure of the scope. It seems like it’s been this way for a while.
> 

I’m assuming that if/when people hit it, they will ping us and ask for a push to stable: I’m just not sure how many people are hitting it at this point.

Cheers
  Trond

> -dros
> 
> On Jan 21, 2014, at 3:21 PM, Weston Andros Adamson <dros@primarydata.com> wrote:
> 
>> cond_resched_lock(cinfo->lock) is called everywhere else while holding
>> the cinfo->lock spinlock.  Not holding this lock while calling
>> transfer_commit_list in filelayout_recover_commit_reqs causes the BUG
>> below.
>> 
>> It's true that we can't hold this lock while calling pnfs_put_lseg,
>> because that might try to lock the inode lock - which might be the
>> same lock as cinfo->lock.
>> 
>> To reproduce, mount a 2 DS pynfs server and run an O_DIRECT command
>> that crosses a stripe boundary and is not page aligned, such as:
>> 
>> dd if=/dev/zero of=/mnt/f bs=17000 count=1 oflag=direct
>> 
>> BUG: sleeping function called from invalid context at linux/fs/nfs/nfs4filelayout.c:1161
>> in_atomic(): 0, irqs_disabled(): 0, pid: 27, name: kworker/0:1
>> 2 locks held by kworker/0:1/27:
>> #0:  (events){.+.+.+}, at: [<ffffffff810501d7>] process_one_work+0x175/0x3a5
>> #1:  ((&dreq->work)){+.+...}, at: [<ffffffff810501d7>] process_one_work+0x175/0x3a5
>> CPU: 0 PID: 27 Comm: kworker/0:1 Not tainted 3.13.0-rc3-branch-dros_testing+ #21
>> Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013
>> Workqueue: events nfs_direct_write_schedule_work [nfs]
>> 0000000000000000 ffff88007a39bbb8 ffffffff81491256 ffff88007b87a130  ffff88007a39bbd8 ffffffff8105f103 ffff880079614000 ffff880079617d40  ffff88007a39bc20 ffffffffa011603e ffff880078988b98 0000000000000000
>> Call Trace:
>> [<ffffffff81491256>] dump_stack+0x4d/0x66
>> [<ffffffff8105f103>] __might_sleep+0x100/0x105
>> [<ffffffffa011603e>] transfer_commit_list+0x94/0xf1 [nfs_layout_nfsv41_files]
>> [<ffffffffa01160d6>] filelayout_recover_commit_reqs+0x3b/0x68 [nfs_layout_nfsv41_files]
>> [<ffffffffa00ba53a>] nfs_direct_write_reschedule+0x9f/0x1d6 [nfs]
>> [<ffffffff810705df>] ? mark_lock+0x1df/0x224
>> [<ffffffff8106e617>] ? trace_hardirqs_off_caller+0x37/0xa4
>> [<ffffffff8106e691>] ? trace_hardirqs_off+0xd/0xf
>> [<ffffffffa00ba8f8>] nfs_direct_write_schedule_work+0x9d/0xb7 [nfs]
>> [<ffffffff810501d7>] ? process_one_work+0x175/0x3a5
>> [<ffffffff81050258>] process_one_work+0x1f6/0x3a5
>> [<ffffffff810501d7>] ? process_one_work+0x175/0x3a5
>> [<ffffffff8105187e>] worker_thread+0x149/0x1f5
>> [<ffffffff81051735>] ? rescuer_thread+0x28d/0x28d
>> [<ffffffff81056d74>] kthread+0xd2/0xda
>> [<ffffffff81056ca2>] ? __kthread_parkme+0x61/0x61
>> [<ffffffff8149e66c>] ret_from_fork+0x7c/0xb0
>> [<ffffffff81056ca2>] ? __kthread_parkme+0x61/0x61
>> 
>> Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
>> ---
>> 
>> I'm pretty sure this is the correct approach - it certainly fixes the BUG
>> for me.
>> 
>> fs/nfs/nfs4filelayout.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>> 
>> diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
>> index 0a93e79..03fd8be 100644
>> --- a/fs/nfs/nfs4filelayout.c
>> +++ b/fs/nfs/nfs4filelayout.c
>> @@ -1216,17 +1216,17 @@ static void filelayout_recover_commit_reqs(struct list_head *dst,
>> 	struct pnfs_commit_bucket *b;
>> 	int i;
>> 
>> -	/* NOTE cinfo->lock is NOT held, relying on fact that this is
>> -	 * only called on single thread per dreq.
>> -	 * Can't take the lock because need to do pnfs_put_lseg
>> -	 */
>> +	spin_lock(cinfo->lock);
>> 	for (i = 0, b = cinfo->ds->buckets; i < cinfo->ds->nbuckets; i++, b++) {
>> 		if (transfer_commit_list(&b->written, dst, cinfo, 0)) {
>> +			spin_unlock(cinfo->lock);
>> 			pnfs_put_lseg(b->wlseg);
>> 			b->wlseg = NULL;
>> +			spin_lock(cinfo->lock);
>> 		}
>> 	}
>> 	cinfo->ds->nwritten = 0;
>> +	spin_unlock(cinfo->lock);
>> }
>> 
>> static unsigned int
>> -- 
>> 1.8.3.4 (Apple Git-47)
>> 
>> --
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> 

--
Trond Myklebust
Linux NFS client maintainer