svc: Clean up deferred requests on transport destruction

A race between svc_revisit and svc_delete_xprt can result in
deferred requests holding references on a transport that can never be
recovered because dead transports are not enqueued for subsequent
processing.

Check for XPT_DEAD in revisit to clean up completing deferrals on a dead
transport and sweep a transport's deferred queue to do the same for queued
but unprocessed deferrals.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 18 insertions, 7 deletions

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 29619612b9f1..a78b87937c73 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -850,6 +850,11 @@ static void svc_age_temp_xprts(unsigned long closure)
 void svc_delete_xprt(struct svc_xprt *xprt)
 {
         struct svc_serv *serv = xprt->xpt_server;
+        struct svc_deferred_req *dr;
+
+        /* Only do this once */
+        if (test_and_set_bit(XPT_DEAD, &xprt->xpt_flags))
+                return;
 
         dprintk("svc: svc_delete_xprt(%p)\n", xprt);
         xprt->xpt_ops->xpo_detach(xprt);
@@ -864,12 +869,16 @@ void svc_delete_xprt(struct svc_xprt *xprt)
          * while still attached to a queue, the queue itself
          * is about to be destroyed (in svc_destroy).
          */
-        if (!test_and_set_bit(XPT_DEAD, &xprt->xpt_flags)) {
-                BUG_ON(atomic_read(&xprt->xpt_ref.refcount) < 2);
-                if (test_bit(XPT_TEMP, &xprt->xpt_flags))
-                        serv->sv_tmpcnt--;
+        if (test_bit(XPT_TEMP, &xprt->xpt_flags))
+                serv->sv_tmpcnt--;
+
+        for (dr = svc_deferred_dequeue(xprt); dr;
+             dr = svc_deferred_dequeue(xprt)) {
                 svc_xprt_put(xprt);
+                kfree(dr);
         }
+
+        svc_xprt_put(xprt);
         spin_unlock_bh(&serv->sv_lock);
 }
 
@@ -915,17 +924,19 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
                 container_of(dreq, struct svc_deferred_req, handle);
         struct svc_xprt *xprt = dr->xprt;
 
-        if (too_many) {
+        spin_lock(&xprt->xpt_lock);
+        set_bit(XPT_DEFERRED, &xprt->xpt_flags);
+        if (too_many || test_bit(XPT_DEAD, &xprt->xpt_flags)) {
+                spin_unlock(&xprt->xpt_lock);
+                dprintk("revisit canceled\n");
                 svc_xprt_put(xprt);
                 kfree(dr);
                 return;
         }
         dprintk("revisit queued\n");
         dr->xprt = NULL;
-        spin_lock(&xprt->xpt_lock);
         list_add(&dr->handle.recent, &xprt->xpt_deferred);
         spin_unlock(&xprt->xpt_lock);
-        set_bit(XPT_DEFERRED, &xprt->xpt_flags);
         svc_xprt_enqueue(xprt);
         svc_xprt_put(xprt);
 }