nfsd: don't try to reuse an expired DRC entry off the list

commit a0ef5e19684f0447da9ff0654a12019c484f57ca upstream.

Currently when we are processing a request, we try to scrape an expired
or over-limit entry off the list in preference to allocating a new one
from the slab.

This is unnecessarily complicated. Just use the slab layer.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index ec8d97ddc63529f3f9bfac15a7a28ef8cd0109b5..02e8e9ad57502fa2ff294181d6f261425bbc5969 100644 (file)
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -128,13 +128,6 @@ nfsd_reply_cache_alloc(void)
        return rp;
 }
 
-static void
-nfsd_reply_cache_unhash(struct svc_cacherep *rp)
-{
-       hlist_del_init(&rp->c_hash);
-       list_del_init(&rp->c_lru);
-}
-
 static void
 nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
 {
@@ -402,22 +395,8 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
 
        /*
         * Since the common case is a cache miss followed by an insert,
-        * preallocate an entry. First, try to reuse the first entry on the LRU
-        * if it works, then go ahead and prune the LRU list.
+        * preallocate an entry.
         */
-       spin_lock(&cache_lock);
-       if (!list_empty(&lru_head)) {
-               rp = list_first_entry(&lru_head, struct svc_cacherep, c_lru);
-               if (nfsd_cache_entry_expired(rp) ||
-                   num_drc_entries >= max_drc_entries) {
-                       nfsd_reply_cache_unhash(rp);
-                       prune_cache_entries();
-                       goto search_cache;
-               }
-       }
-
-       /* No expired ones available, allocate a new one. */
-       spin_unlock(&cache_lock);
        rp = nfsd_reply_cache_alloc();
        spin_lock(&cache_lock);
        if (likely(rp)) {
@@ -425,7 +404,9 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
                drc_mem_usage += sizeof(*rp);
        }
 
-search_cache:
+       /* go ahead and prune the cache */
+       prune_cache_entries();
+
        found = nfsd_cache_search(rqstp, csum);
        if (found) {
                if (likely(rp))
@@ -439,15 +420,6 @@ search_cache:
                goto out;
        }
 
-       /*
-        * We're keeping the one we just allocated. Are we now over the
-        * limit? Prune one off the tip of the LRU in trade for the one we
-        * just allocated if so.
-        */
-       if (num_drc_entries >= max_drc_entries)
-               nfsd_reply_cache_free_locked(list_first_entry(&lru_head,
-                                               struct svc_cacherep, c_lru));
-
        nfsdstats.rcmisses++;
        rqstp->rq_cacherep = rp;
        rp->c_state = RC_INPROG;