[PATCH] NLM: fix a client-side race on blocking locks.

 If the lock blocks, the server may send us a GRANTED message that
 races with the reply to our LOCK request. Make sure that we catch
 the GRANTED by queueing up our request on the nlm_blocked list
 before we send off the first LOCK rpc call.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 32 insertions, 8 deletions

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index a4407619b1f..fd77ed1d710 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -21,6 +21,7 @@
 
 #define NLMDBG_FACILITY         NLMDBG_CLIENT
 #define NLMCLNT_GRACE_WAIT      (5*HZ)
+#define NLMCLNT_POLL_TIMEOUT    (30*HZ)
 
 static int      nlmclnt_test(struct nlm_rqst *, struct file_lock *);
 static int      nlmclnt_lock(struct nlm_rqst *, struct file_lock *);
@@ -553,7 +554,8 @@ nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
 {
         struct nlm_host *host = req->a_host;
         struct nlm_res  *resp = &req->a_res;
-        int             status;
+        long timeout;
+        int status;
 
         if (!host->h_monitored && nsm_monitor(host) < 0) {
                 printk(KERN_NOTICE "lockd: failed to monitor %s\n",
@@ -562,15 +564,32 @@ nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
                 goto out;
         }
 
-        do {
-                if ((status = nlmclnt_call(req, NLMPROC_LOCK)) >= 0) {
-                        if (resp->status != NLM_LCK_BLOCKED)
-                                break;
-                        status = nlmclnt_block(host, fl, &resp->status);
-                }
+        if (req->a_args.block) {
+                status = nlmclnt_prepare_block(req, host, fl);
                 if (status < 0)
                         goto out;
-        } while (resp->status == NLM_LCK_BLOCKED && req->a_args.block);
+        }
+        for(;;) {
+                status = nlmclnt_call(req, NLMPROC_LOCK);
+                if (status < 0)
+                        goto out_unblock;
+                if (resp->status != NLM_LCK_BLOCKED)
+                        break;
+                /* Wait on an NLM blocking lock */
+                timeout = nlmclnt_block(req, NLMCLNT_POLL_TIMEOUT);
+                /* Did a reclaimer thread notify us of a server reboot? */
+                if (resp->status ==  NLM_LCK_DENIED_GRACE_PERIOD)
+                        continue;
+                if (resp->status != NLM_LCK_BLOCKED)
+                        break;
+                if (timeout >= 0)
+                        continue;
+                /* We were interrupted. Send a CANCEL request to the server
+                 * and exit
+                 */
+                status = (int)timeout;
+                goto out_unblock;
+        }
 
         if (resp->status == NLM_LCK_GRANTED) {
                 fl->fl_u.nfs_fl.state = host->h_state;
@@ -579,6 +598,11 @@ nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
                 do_vfs_lock(fl);
         }
         status = nlm_stat_to_errno(resp->status);
+out_unblock:
+        nlmclnt_finish_block(req);
+        /* Cancel the blocked request if it is still pending */
+        if (resp->status == NLM_LCK_BLOCKED)
+                nlmclnt_cancel(host, fl);
 out:
         nlmclnt_release_lockargs(req);
         return status;