[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/clntlock.c b/fs/lockd/clntlock.c
index 44adb84..006bb9e 100644
--- a/fs/lockd/clntlock.c
+++ b/fs/lockd/clntlock.c
@@ -42,23 +42,51 @@
static LIST_HEAD(nlm_blocked);
/*
+ * Queue up a lock for blocking so that the GRANTED request can see it
+ */
+int nlmclnt_prepare_block(struct nlm_rqst *req, struct nlm_host *host, struct file_lock *fl)
+{
+ struct nlm_wait *block;
+
+ BUG_ON(req->a_block != NULL);
+ block = kmalloc(sizeof(*block), GFP_KERNEL);
+ if (block == NULL)
+ return -ENOMEM;
+ block->b_host = host;
+ block->b_lock = fl;
+ init_waitqueue_head(&block->b_wait);
+ block->b_status = NLM_LCK_BLOCKED;
+
+ list_add(&block->b_list, &nlm_blocked);
+ req->a_block = block;
+
+ return 0;
+}
+
+void nlmclnt_finish_block(struct nlm_rqst *req)
+{
+ struct nlm_wait *block = req->a_block;
+
+ if (block == NULL)
+ return;
+ req->a_block = NULL;
+ list_del(&block->b_list);
+ kfree(block);
+}
+
+/*
* Block on a lock
*/
-int
-nlmclnt_block(struct nlm_host *host, struct file_lock *fl, u32 *statp)
+long nlmclnt_block(struct nlm_rqst *req, long timeout)
{
- struct nlm_wait block, **head;
- int err;
- u32 pstate;
+ struct nlm_wait *block = req->a_block;
+ long ret;
- block.b_host = host;
- block.b_lock = fl;
- init_waitqueue_head(&block.b_wait);
- block.b_status = NLM_LCK_BLOCKED;
- list_add(&block.b_list, &nlm_blocked);
-
- /* Remember pseudo nsm state */
- pstate = host->h_state;
+ /* A borken server might ask us to block even if we didn't
+ * request it. Just say no!
+ */
+ if (!req->a_args.block)
+ return -EAGAIN;
/* Go to sleep waiting for GRANT callback. Some servers seem
* to lose callbacks, however, so we're going to poll from
@@ -68,23 +96,16 @@
* a 1 minute timeout would do. See the comment before
* nlmclnt_lock for an explanation.
*/
- sleep_on_timeout(&block.b_wait, 30*HZ);
+ ret = wait_event_interruptible_timeout(block->b_wait,
+ block->b_status != NLM_LCK_BLOCKED,
+ timeout);
- list_del(&block.b_list);
-
- if (!signalled()) {
- *statp = block.b_status;
- return 0;
+ if (block->b_status != NLM_LCK_BLOCKED) {
+ req->a_res.status = block->b_status;
+ block->b_status = NLM_LCK_BLOCKED;
}
- /* Okay, we were interrupted. Cancel the pending request
- * unless the server has rebooted.
- */
- if (pstate == host->h_state && (err = nlmclnt_cancel(host, fl)) < 0)
- printk(KERN_NOTICE
- "lockd: CANCEL call failed (errno %d)\n", -err);
-
- return -ERESTARTSYS;
+ return ret;
}
/*
@@ -94,27 +115,23 @@
nlmclnt_grant(struct nlm_lock *lock)
{
struct nlm_wait *block;
+ u32 res = nlm_lck_denied;
/*
* Look up blocked request based on arguments.
* Warning: must not use cookie to match it!
*/
list_for_each_entry(block, &nlm_blocked, b_list) {
- if (nlm_compare_locks(block->b_lock, &lock->fl))
- break;
+ if (nlm_compare_locks(block->b_lock, &lock->fl)) {
+ /* Alright, we found a lock. Set the return status
+ * and wake up the caller
+ */
+ block->b_status = NLM_LCK_GRANTED;
+ wake_up(&block->b_wait);
+ res = nlm_granted;
+ }
}
-
- /* Ooops, no blocked request found. */
- if (block == NULL)
- return nlm_lck_denied;
-
- /* Alright, we found the lock. Set the return status and
- * wake up the caller.
- */
- block->b_status = NLM_LCK_GRANTED;
- wake_up(&block->b_wait);
-
- return nlm_granted;
+ return res;
}
/*