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authorNeilBrown <neilb@suse.de>2010-02-03 17:31:31 +1100
committerJ. Bruce Fields <bfields@citi.umich.edu>2010-03-14 21:48:52 -0400
commitd202cce8963d9268ff355a386e20243e8332b308 (patch)
treedf95cd2ee9b5fc9663b8fa97e81a4ff1387f2d6e /net/sunrpc
parent2f50d8b63dd6e5320a9d223298df19df3502da29 (diff)
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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>
Diffstat (limited to 'net/sunrpc')
-rw-r--r--net/sunrpc/cache.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 9826c5ceb995..3e1ef8bf4dc2 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -59,7 +59,7 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
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 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
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 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
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 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
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 int cache_make_upcall(struct cache_detail *cd, 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) ||
- cache_is_expired(detail, h))
+ if (!test_bit(CACHE_VALID, &h->flags))
return -EAGAIN;
else {
/* entry is valid */