NLM: Fix reclaim races
Currently it is possible for a task to remove its locks at the same time as
the NLM recovery thread is trying to recover them. This quickly leads to an
Oops.
Protect the locks using an rw semaphore while they are being recovered.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/lockd/clntlock.c b/fs/lockd/clntlock.c
index bce7444..52774fe 100644
--- a/fs/lockd/clntlock.c
+++ b/fs/lockd/clntlock.c
@@ -147,11 +147,10 @@
* Someone has sent us an SM_NOTIFY. Ensure we bind to the new port number,
* that we mark locks for reclaiming, and that we bump the pseudo NSM state.
*/
-static inline
-void nlmclnt_prepare_reclaim(struct nlm_host *host, u32 newstate)
+static void nlmclnt_prepare_reclaim(struct nlm_host *host)
{
+ down_write(&host->h_rwsem);
host->h_monitored = 0;
- host->h_nsmstate = newstate;
host->h_state++;
host->h_nextrebind = 0;
nlm_rebind_host(host);
@@ -164,6 +163,13 @@
dprintk("NLM: reclaiming locks for host %s", host->h_name);
}
+static void nlmclnt_finish_reclaim(struct nlm_host *host)
+{
+ host->h_reclaiming = 0;
+ up_write(&host->h_rwsem);
+ dprintk("NLM: done reclaiming locks for host %s", host->h_name);
+}
+
/*
* Reclaim all locks on server host. We do this by spawning a separate
* reclaimer thread.
@@ -171,12 +177,10 @@
void
nlmclnt_recovery(struct nlm_host *host, u32 newstate)
{
- if (host->h_reclaiming++) {
- if (host->h_nsmstate == newstate)
- return;
- nlmclnt_prepare_reclaim(host, newstate);
- } else {
- nlmclnt_prepare_reclaim(host, newstate);
+ if (host->h_nsmstate == newstate)
+ return;
+ host->h_nsmstate = newstate;
+ if (!host->h_reclaiming++) {
nlm_get_host(host);
__module_get(THIS_MODULE);
if (kernel_thread(reclaimer, host, CLONE_KERNEL) < 0)
@@ -190,6 +194,7 @@
struct nlm_host *host = (struct nlm_host *) ptr;
struct nlm_wait *block;
struct file_lock *fl, *next;
+ u32 nsmstate;
daemonize("%s-reclaim", host->h_name);
allow_signal(SIGKILL);
@@ -199,19 +204,25 @@
lock_kernel();
lockd_up();
+ nlmclnt_prepare_reclaim(host);
/* First, reclaim all locks that have been marked. */
restart:
+ nsmstate = host->h_nsmstate;
list_for_each_entry_safe(fl, next, &host->h_reclaim, fl_u.nfs_fl.list) {
list_del_init(&fl->fl_u.nfs_fl.list);
if (signalled())
continue;
- if (nlmclnt_reclaim(host, fl) == 0)
- list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
- goto restart;
+ if (nlmclnt_reclaim(host, fl) != 0)
+ continue;
+ list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
+ if (host->h_nsmstate != nsmstate) {
+ /* Argh! The server rebooted again! */
+ list_splice_init(&host->h_granted, &host->h_reclaim);
+ goto restart;
+ }
}
-
- host->h_reclaiming = 0;
+ nlmclnt_finish_reclaim(host);
/* Now, wake up all processes that sleep on a blocked lock */
list_for_each_entry(block, &nlm_blocked, b_list) {
diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index f96e381..4db6209 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -508,7 +508,10 @@
}
block = nlmclnt_prepare_block(host, fl);
+again:
for(;;) {
+ /* Reboot protection */
+ fl->fl_u.nfs_fl.state = host->h_state;
status = nlmclnt_call(req, NLMPROC_LOCK);
if (status < 0)
goto out_unblock;
@@ -531,10 +534,16 @@
}
if (resp->status == NLM_LCK_GRANTED) {
- fl->fl_u.nfs_fl.state = host->h_state;
+ down_read(&host->h_rwsem);
+ /* Check whether or not the server has rebooted */
+ if (fl->fl_u.nfs_fl.state != host->h_state) {
+ up_read(&host->h_rwsem);
+ goto again;
+ }
fl->fl_flags |= FL_SLEEP;
/* Ensure the resulting lock will get added to granted list */
do_vfs_lock(fl);
+ up_read(&host->h_rwsem);
}
status = nlm_stat_to_errno(resp->status);
out_unblock:
@@ -596,6 +605,7 @@
static int
nlmclnt_unlock(struct nlm_rqst *req, struct file_lock *fl)
{
+ struct nlm_host *host = req->a_host;
struct nlm_res *resp = &req->a_res;
int status;
@@ -604,7 +614,9 @@
* request, or to deny it with NLM_LCK_DENIED_GRACE_PERIOD. In either
* case, we want to unlock.
*/
+ down_read(&host->h_rwsem);
do_vfs_lock(fl);
+ up_read(&host->h_rwsem);
if (req->a_flags & RPC_TASK_ASYNC)
return nlm_async_call(req, NLMPROC_UNLOCK, &nlmclnt_unlock_ops);
diff --git a/fs/lockd/host.c b/fs/lockd/host.c
index 5242743..38b0e8a 100644
--- a/fs/lockd/host.c
+++ b/fs/lockd/host.c
@@ -117,6 +117,7 @@
host->h_expires = jiffies + NLM_HOST_EXPIRE;
atomic_set(&host->h_count, 1);
init_waitqueue_head(&host->h_gracewait);
+ init_rwsem(&host->h_rwsem);
host->h_state = 0; /* pseudo NSM state */
host->h_nsmstate = 0; /* real NSM state */
host->h_server = server;
diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index a6c1a33..6b26847 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -50,6 +50,7 @@
h_killed : 1,
h_monitored : 1;
wait_queue_head_t h_gracewait; /* wait while reclaiming */
+ struct rw_semaphore h_rwsem; /* Reboot recovery lock */
u32 h_state; /* pseudo-state counter */
u32 h_nsmstate; /* true remote NSM state */
u32 h_pidcount; /* Pseudopids */