[PATCH 04/12] sunrpc/cache: recheck cache validity after cache_defer_req

NeilBrown
2009-08-04T05:24:34Z

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>
---

net/sunrpc/cache.c | 53 ++++++++++++++++++++++++++++++++--------------------
1 files changed, 33 insertions(+), 20 deletions(-)

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index c1f897c..bff4baa 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -173,6 +173,22 @@ 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.
@@ -181,8 +197,10 @@ 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,
@@ -192,17 +210,7 @@ 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);
@@ -235,10 +243,14 @@ 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;
@@ -557,11 +569,11 @@ 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;

@@ -591,8 +603,9 @@ 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)