lockd: nlmclnt_reclaim(): avoid stack overflow

Even though nlmclnt_reclaim() is only one call into the stack frame,
928 bytes on the stack seems like a lot. Recode to dynamically
allocate the request structure once from within the reclaimer task,
then pass this pointer into nlmclnt_reclaim() for reuse on
subsequent calls.

smatch analysis:

fs/lockd/clntproc.c:620 nlmclnt_reclaim() warn: 'reqst' puts
 928 bytes on stack

Also remove redundant assignment of 0 after memset.

Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

2 files changed, 13 insertions, 5 deletions

diff --git a/fs/lockd/clntlock.c b/fs/lockd/clntlock.c
index 4885b53e56bd..6cd673d34fb9 100644
--- a/fs/lockd/clntlock.c
+++ b/fs/lockd/clntlock.c
@@ -220,10 +220,19 @@ reclaimer(void *ptr)
 {
         struct nlm_host   *host = (struct nlm_host *) ptr;
         struct nlm_wait   *block;
+        struct nlm_rqst   *req;
         struct file_lock *fl, *next;
         u32 nsmstate;
         struct net *net = host->net;
 
+        req = kmalloc(sizeof(*req), GFP_KERNEL);
+        if (!req) {
+                printk(KERN_ERR "lockd: reclaimer unable to alloc memory."
+                                " Locks for %s won't be reclaimed!\n",
+                                host->h_name);
+                return 0;
+        }
+
         allow_signal(SIGKILL);
 
         down_write(&host->h_rwsem);
@@ -253,7 +262,7 @@ restart:
                  */
                 if (signalled())
                         continue;
-                if (nlmclnt_reclaim(host, fl) != 0)
+                if (nlmclnt_reclaim(host, fl, req) != 0)
                         continue;
                 list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
                 if (host->h_nsmstate != nsmstate) {
@@ -279,5 +288,6 @@ restart:
         /* Release host handle after use */
         nlmclnt_release_host(host);
         lockd_down(net);
+        kfree(req);
         return 0;
 }
diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index 54f9e6ce0430..b43114c4332a 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -615,17 +615,15 @@ out_unlock:
  * RECLAIM: Try to reclaim a lock
  */
 int
-nlmclnt_reclaim(struct nlm_host *host, struct file_lock *fl)
+nlmclnt_reclaim(struct nlm_host *host, struct file_lock *fl,
+                struct nlm_rqst *req)
 {
-        struct nlm_rqst reqst, *req;
         int             status;
 
-        req = &reqst;
         memset(req, 0, sizeof(*req));
         locks_init_lock(&req->a_args.lock.fl);
         locks_init_lock(&req->a_res.lock.fl);
         req->a_host  = host;
-        req->a_flags = 0;
 
         /* Set up the argument struct */
         nlmclnt_setlockargs(req, fl);