sunrpc: never return expired entries in sunrpc_cache_lookup
If sunrpc_cache_lookup finds an expired entry, remove it from
the cache and return a freshly created non-VALID entry instead.
This ensures that we only ever get a usable entry, or an
entry that will become usable once an update arrives.
i.e. we will never need to repeat the lookup.
This allows us to remove the 'is_expired' test from cache_check
(i.e. from cache_is_valid). cache_check should never get an expired
entry as 'lookup' will never return one. If it does happen - due to
inconvenient timing - then just accept it as still valid, it won't be
very much past it's use-by date.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 9826c5c..3e1ef8b 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -59,7 +59,7 @@
struct cache_head *key, int hash)
{
struct cache_head **head, **hp;
- struct cache_head *new = NULL;
+ struct cache_head *new = NULL, *freeme = NULL;
head = &detail->hash_table[hash];
@@ -68,6 +68,9 @@
for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
struct cache_head *tmp = *hp;
if (detail->match(tmp, key)) {
+ if (cache_is_expired(detail, tmp))
+ /* This entry is expired, we will discard it. */
+ break;
cache_get(tmp);
read_unlock(&detail->hash_lock);
return tmp;
@@ -92,6 +95,13 @@
for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
struct cache_head *tmp = *hp;
if (detail->match(tmp, key)) {
+ if (cache_is_expired(detail, tmp)) {
+ *hp = tmp->next;
+ tmp->next = NULL;
+ detail->entries --;
+ freeme = tmp;
+ break;
+ }
cache_get(tmp);
write_unlock(&detail->hash_lock);
cache_put(new, detail);
@@ -104,6 +114,8 @@
cache_get(new);
write_unlock(&detail->hash_lock);
+ if (freeme)
+ cache_put(freeme, detail);
return new;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
@@ -189,8 +201,7 @@
static inline int cache_is_valid(struct cache_detail *detail, struct cache_head *h)
{
- if (!test_bit(CACHE_VALID, &h->flags) ||
- cache_is_expired(detail, h))
+ if (!test_bit(CACHE_VALID, &h->flags))
return -EAGAIN;
else {
/* entry is valid */