diff options
Diffstat (limited to 'net/sunrpc/cache.c')
-rw-r--r-- | net/sunrpc/cache.c | 54 |
1 files changed, 39 insertions, 15 deletions
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index e433e75..72ad836 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) |