NLM: Ensure that nlmclnt_cancel_callback() doesn't loop forever

 If the server returns NLM_LCK_DENIED_NOLOCKS, we currently retry the
 entire NLM_CANCEL request. This may end up looping forever unless the
 server changes its mind (why would it do that, though?).

 Ensure that we limit the number of retries (to 3).

 See bug# 5957 in bugzilla.kernel.org.

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

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index b8ecfa1..220058d 100644 (file)
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -22,6 +22,7 @@
 #define NLMDBG_FACILITY                NLMDBG_CLIENT
 #define NLMCLNT_GRACE_WAIT     (5*HZ)
 #define NLMCLNT_POLL_TIMEOUT   (30*HZ)
+#define NLMCLNT_MAX_RETRIES    3
 
 static int     nlmclnt_test(struct nlm_rqst *, struct file_lock *);
 static int     nlmclnt_lock(struct nlm_rqst *, struct file_lock *);
@@ -802,6 +803,9 @@ die:
        return;
 
 retry_cancel:
+       /* Don't ever retry more than 3 times */
+       if (req->a_retries++ >= NLMCLNT_MAX_RETRIES)
+               goto die;
        nlm_rebind_host(req->a_host);
        rpc_restart_call(task);
        rpc_delay(task, 30 * HZ);

diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index afe9a8f..920766c 100644 (file)
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -84,6 +84,7 @@ struct nlm_rqst {
        struct nlm_args         a_args;         /* arguments */
        struct nlm_res          a_res;          /* result */
        struct nlm_wait *       a_block;
+       unsigned int            a_retries;      /* Retry count */
        char                    a_owner[NLMCLNT_OHSIZE];
 };