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Subject: Re: [PATCH] pnfs: fix BUG in filelayout_recover_commit_reqs
From: Weston Andros Adamson <dros@primarydata.com>
In-Reply-To: <1390335693-12004-1-git-send-email-dros@primarydata.com>
Date: Wed, 22 Jan 2014 09:19:30 -0500
Cc: Trond Myklebust <trond.myklebust@primarydata.com>,
        linux-nfs list <linux-nfs@vger.kernel.org>
Message-Id: <429FC150-5092-415D-A411-1F4A35EAAB58@primarydata.com>
References: <1390335693-12004-1-git-send-email-dros@primarydata.com>
To: Weston Andros Adamson <dros@primarydata.com>
Sender: linux-nfs-owner@vger.kernel.org
List-ID: <linux-nfs.vger.kernel.org>

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.

-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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