linux-kernel - [ 032/108] NFSv4.1: Remove a bogus BUG_ON() in nfs4_layoutreturn

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Date:	Wed, 12 Sep 2012 16:28:30 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Boaz Harrosh <bharrosh@...asas.com>,
	Tigran Mkrtchyan <tigran.mkrtchyan@...y.de>,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [ 032/108] NFSv4.1: Remove a bogus BUG_ON() in nfs4_layoutreturn_done

From: Greg KH <gregkh@...uxfoundation.org>

3.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <Trond.Myklebust@...app.com>

commit 47fbf7976e0b7d9dcdd799e2a1baba19064d9631 upstream.

Ever since commit 0a57cdac3f (NFSv4.1 send layoutreturn to fence
disconnected data server) we've been sending layoutreturn calls
while there is potentially still outstanding I/O to the data
servers. The reason we do this is to avoid races between replayed
writes to the MDS and the original writes to the DS.

When this happens, the BUG_ON() in nfs4_layoutreturn_done can
be triggered because it assumes that we would never call
layoutreturn without knowing that all I/O to the DS is
finished. The fix is to remove the BUG_ON() now that the
assumptions behind the test are obsolete.

Reported-by: Boaz Harrosh <bharrosh@...asas.com>
Reported-by: Tigran Mkrtchyan <tigran.mkrtchyan@...y.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/nfs4proc.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6300,12 +6300,8 @@ static void nfs4_layoutreturn_done(struc
 		return;
 	}
 	spin_lock(&lo->plh_inode->i_lock);
-	if (task->tk_status == 0) {
-		if (lrp->res.lrs_present) {
-			pnfs_set_layout_stateid(lo, &lrp->res.stateid, true);
-		} else
-			BUG_ON(!list_empty(&lo->plh_segs));
-	}
+	if (task->tk_status == 0 && lrp->res.lrs_present)
+		pnfs_set_layout_stateid(lo, &lrp->res.stateid, true);
 	lo->plh_block_lgets--;
 	spin_unlock(&lo->plh_inode->i_lock);
 	dprintk("<-- %s\n", __func__);


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