[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;
}
/*
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;
diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index 0d9d225..16d4e5a 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -72,6 +72,8 @@
uint32_t pid;
};
+struct nlm_wait;
+
/*
* Memory chunk for NLM client RPC request.
*/
@@ -81,6 +83,7 @@
struct nlm_host * a_host; /* host handle */
struct nlm_args a_args; /* arguments */
struct nlm_res a_res; /* result */
+ struct nlm_wait * a_block;
char a_owner[NLMCLNT_OHSIZE];
};
@@ -142,7 +145,9 @@
* Lockd client functions
*/
struct nlm_rqst * nlmclnt_alloc_call(void);
-int nlmclnt_block(struct nlm_host *, struct file_lock *, u32 *);
+int nlmclnt_prepare_block(struct nlm_rqst *req, struct nlm_host *host, struct file_lock *fl);
+void nlmclnt_finish_block(struct nlm_rqst *req);
+long nlmclnt_block(struct nlm_rqst *req, long timeout);
int nlmclnt_cancel(struct nlm_host *, struct file_lock *);
u32 nlmclnt_grant(struct nlm_lock *);
void nlmclnt_recovery(struct nlm_host *, u32);