From: Jeff Layton <jlayton@redhat.com>
Date: Thu, 5 Dec 2013 11:00:51 +0000 (-0500)
Subject: nfsd: don't try to reuse an expired DRC entry off the list
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=03e9dd7847298ea8328b914de8f4777e238cdb77;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git

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 ec8d97ddc635..02e8e9ad5750 100644
--- 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;