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-rw-r--r--net/sunrpc/cache.c54
1 files changed, 39 insertions, 15 deletions
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index e433e7580e27..72ad836e4fe0 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -37,7 +37,7 @@
#define RPCDBG_FACILITY RPCDBG_CACHE
-static void cache_defer_req(struct cache_req *req, struct cache_head *item);
+static bool cache_defer_req(struct cache_req *req, struct cache_head *item);
static void cache_revisit_request(struct cache_head *item);
static void cache_init(struct cache_head *h)
@@ -128,6 +128,7 @@ static void cache_fresh_locked(struct cache_head *head, time_t expiry)
{
head->expiry_time = expiry;
head->last_refresh = seconds_since_boot();
+ smp_wmb(); /* paired with smp_rmb() in cache_is_valid() */
set_bit(CACHE_VALID, &head->flags);
}
@@ -208,11 +209,36 @@ static inline int cache_is_valid(struct cache_detail *detail, struct cache_head
/* entry is valid */
if (test_bit(CACHE_NEGATIVE, &h->flags))
return -ENOENT;
- else
+ else {
+ /*
+ * In combination with write barrier in
+ * sunrpc_cache_update, ensures that anyone
+ * using the cache entry after this sees the
+ * updated contents:
+ */
+ smp_rmb();
return 0;
+ }
}
}
+static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h)
+{
+ int rv;
+
+ write_lock(&detail->hash_lock);
+ rv = cache_is_valid(detail, h);
+ if (rv != -EAGAIN) {
+ write_unlock(&detail->hash_lock);
+ return rv;
+ }
+ set_bit(CACHE_NEGATIVE, &h->flags);
+ cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
+ write_unlock(&detail->hash_lock);
+ cache_fresh_unlocked(h, detail);
+ return -ENOENT;
+}
+
/*
* This is the generic cache management routine for all
* the authentication caches.
@@ -251,14 +277,8 @@ int cache_check(struct cache_detail *detail,
case -EINVAL:
clear_bit(CACHE_PENDING, &h->flags);
cache_revisit_request(h);
- if (rv == -EAGAIN) {
- set_bit(CACHE_NEGATIVE, &h->flags);
- cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
- cache_fresh_unlocked(h, detail);
- rv = -ENOENT;
- }
+ rv = try_to_negate_entry(detail, h);
break;
-
case -EAGAIN:
clear_bit(CACHE_PENDING, &h->flags);
cache_revisit_request(h);
@@ -268,9 +288,11 @@ int cache_check(struct cache_detail *detail,
}
if (rv == -EAGAIN) {
- cache_defer_req(rqstp, h);
- if (!test_bit(CACHE_PENDING, &h->flags)) {
- /* Request is not deferred */
+ if (!cache_defer_req(rqstp, h)) {
+ /*
+ * Request was not deferred; handle it as best
+ * we can ourselves:
+ */
rv = cache_is_valid(detail, h);
if (rv == -EAGAIN)
rv = -ETIMEDOUT;
@@ -618,18 +640,19 @@ static void cache_limit_defers(void)
discard->revisit(discard, 1);
}
-static void cache_defer_req(struct cache_req *req, struct cache_head *item)
+/* Return true if and only if a deferred request is queued. */
+static bool cache_defer_req(struct cache_req *req, struct cache_head *item)
{
struct cache_deferred_req *dreq;
if (req->thread_wait) {
cache_wait_req(req, item);
if (!test_bit(CACHE_PENDING, &item->flags))
- return;
+ return false;
}
dreq = req->defer(req);
if (dreq == NULL)
- return;
+ return false;
setup_deferral(dreq, item, 1);
if (!test_bit(CACHE_PENDING, &item->flags))
/* Bit could have been cleared before we managed to
@@ -638,6 +661,7 @@ static void cache_defer_req(struct cache_req *req, struct cache_head *item)
cache_revisit_request(item);
cache_limit_defers();
+ return true;
}
static void cache_revisit_request(struct cache_head *item)