sunrpc/cache: recheck cache validity after cache_defer_req

If cache_defer_req did not leave the request on a queue, then it could
possibly have waited long enough that the cache became valid.  So check the
status after the call.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 33 insertions, 20 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 44f45166378a..bbd31f1215e7 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -176,6 +176,22 @@ struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
 EXPORT_SYMBOL_GPL(sunrpc_cache_update);
 
 static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h);
+
+static inline int cache_is_valid(struct cache_detail *detail, struct cache_head *h)
+{
+        if (!test_bit(CACHE_VALID, &h->flags) ||
+            h->expiry_time < get_seconds())
+                return -EAGAIN;
+        else if (detail->flush_time > h->last_refresh)
+                return -EAGAIN;
+        else {
+                /* entry is valid */
+                if (test_bit(CACHE_NEGATIVE, &h->flags))
+                        return -ENOENT;
+                else
+                        return 0;
+        }
+}
 /*
  * This is the generic cache management routine for all
  * the authentication caches.
@@ -184,8 +200,10 @@ static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h);
  *
  *
  * Returns 0 if the cache_head can be used, or cache_puts it and returns
- * -EAGAIN if upcall is pending,
- * -ETIMEDOUT if upcall failed and should be retried,
+ * -EAGAIN if upcall is pending and request has been queued
+ * -ETIMEDOUT if upcall failed or request could not be queue or
+ *           upcall completed but item is still invalid (implying that
+ *           the cache item has been replaced with a newer one).
  * -ENOENT if cache entry was negative
  */
 int cache_check(struct cache_detail *detail,
@@ -195,17 +213,7 @@ int cache_check(struct cache_detail *detail,
         long refresh_age, age;
 
         /* First decide return status as best we can */
-        if (!test_bit(CACHE_VALID, &h->flags) ||
-            h->expiry_time < get_seconds())
-                rv = -EAGAIN;
-        else if (detail->flush_time > h->last_refresh)
-                rv = -EAGAIN;
-        else {
-                /* entry is valid */
-                if (test_bit(CACHE_NEGATIVE, &h->flags))
-                        rv = -ENOENT;
-                else rv = 0;
-        }
+        rv = cache_is_valid(detail, h);
 
         /* now see if we want to start an upcall */
         refresh_age = (h->expiry_time - h->last_refresh);
@@ -238,10 +246,14 @@ int cache_check(struct cache_detail *detail,
                 }
         }
 
-        if (rv == -EAGAIN)
-                if (cache_defer_req(rqstp, h) != 0)
-                        rv = -ETIMEDOUT;
-
+        if (rv == -EAGAIN) {
+                if (cache_defer_req(rqstp, h) == 0) {
+                        /* Request is not deferred */
+                        rv = cache_is_valid(detail, h);
+                        if (rv == -EAGAIN)
+                                rv = -ETIMEDOUT;
+                }
+        }
         if (rv)
                 cache_put(h, detail);
         return rv;
@@ -560,11 +572,11 @@ static int cache_defer_req(struct cache_req *req, struct cache_head *item)
                  * or continue and drop the oldest below
                  */
                 if (net_random()&1)
-                        return -ETIMEDOUT;
+                        return 0;
         }
         dreq = req->defer(req);
         if (dreq == NULL)
-                return -ETIMEDOUT;
+                return 0;
 
         dreq->item = item;
 
@@ -594,8 +606,9 @@ static int cache_defer_req(struct cache_req *req, struct cache_head *item)
         if (!test_bit(CACHE_PENDING, &item->flags)) {
                 /* must have just been validated... */
                 cache_revisit_request(item);
+                return 0;
         }
-        return 0;
+        return 1;
 }
 
 static void cache_revisit_request(struct cache_head *item)