linux-kernel - [044/118] LOCKD: Ensure that nlmclnt_block resets block->b

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Message-ID: <lsq.1368193181.95318870@decadent.org.uk>
Date:	Fri, 10 May 2013 14:39:41 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Marc Eshel" <eshel@...ibm.com>,
	"Trond Myklebust" <Trond.Myklebust@...app.com>
Subject: [044/118] LOCKD: Ensure that nlmclnt_block resets block->b_status
 after a server reboot

3.2.45-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit 1dfd89af8697a299e7982ae740d4695ecd917eef upstream.

After a server reboot, the reclaimer thread will recover all the existing
locks. For locks that are blocked, however, it will change the value
of block->b_status to nlm_lck_denied_grace_period in order to signal that
they need to wake up and resend the original blocking lock request.

Due to a bug, however, the block->b_status never gets reset after the
blocked locks have been woken up, and so the process goes into an
infinite loop of resends until the blocked lock is satisfied.

Reported-by: Marc Eshel <eshel@...ibm.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/lockd/clntlock.c |    3 +++
 fs/lockd/clntproc.c |    3 ---
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/fs/lockd/clntlock.c
+++ b/fs/lockd/clntlock.c
@@ -141,6 +141,9 @@ int nlmclnt_block(struct nlm_wait *block
 			timeout);
 	if (ret < 0)
 		return -ERESTARTSYS;
+	/* Reset the lock status after a server reboot so we resend */
+	if (block->b_status == nlm_lck_denied_grace_period)
+		block->b_status = nlm_lck_blocked;
 	req->a_res.status = block->b_status;
 	return 0;
 }
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -551,9 +551,6 @@ again:
 		status = nlmclnt_block(block, req, NLMCLNT_POLL_TIMEOUT);
 		if (status < 0)
 			break;
-		/* Resend the blocking lock request after a server reboot */
-		if (resp->status ==  nlm_lck_denied_grace_period)
-			continue;
 		if (resp->status != nlm_lck_blocked)
 			break;
 	}

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