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| author | NeilBrown <neilb@suse.de> | 2010-02-03 09:31:31 +0300 |
|---|---|---|
| committer | J. Bruce Fields <bfields@citi.umich.edu> | 2010-03-15 04:48:52 +0300 |
| commit | d202cce8963d9268ff355a386e20243e8332b308 (patch) | |
| tree | df95cd2ee9b5fc9663b8fa97e81a4ff1387f2d6e /net/sunrpc/cache.c | |
| parent | 2f50d8b63dd6e5320a9d223298df19df3502da29 (diff) | |
| download | linux-d202cce8963d9268ff355a386e20243e8332b308.tar.xz | |
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/cache.c')
| -rw-r--r-- | net/sunrpc/cache.c | 17 |
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 */ |