[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>
diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index a440761..fd77ed1 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 @@
{
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 @@
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 @@
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;