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/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);