nfsd: convert num_drc_entries to an atomic_t

...so we can remove the spinlocking around it.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 12 insertions, 16 deletions

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 8abec475f80f..dc909091349b 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -47,7 +47,7 @@ static unsigned int		drc_hashsize;
  */
 
 /* total number of entries */
-static unsigned int             num_drc_entries;
+static atomic_t                 num_drc_entries;
 
 /* cache misses due only to checksum comparison failures */
 static unsigned int             payload_misses;
@@ -148,7 +148,7 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
                 kfree(rp->c_replvec.iov_base);
         }
         list_del(&rp->c_lru);
-        --num_drc_entries;
+        atomic_dec(&num_drc_entries);
         drc_mem_usage -= sizeof(*rp);
         kmem_cache_free(drc_slab, rp);
 }
@@ -167,7 +167,7 @@ int nfsd_reply_cache_init(void)
         unsigned int i;
 
         max_drc_entries = nfsd_cache_size_limit();
-        num_drc_entries = 0;
+        atomic_set(&num_drc_entries, 0);
         hashsize = nfsd_hashsize(max_drc_entries);
         maskbits = ilog2(hashsize);
 
@@ -242,7 +242,7 @@ prune_bucket(struct nfsd_drc_bucket *b)
                  */
                 if (rp->c_state == RC_INPROG)
                         continue;
-                if (num_drc_entries <= max_drc_entries &&
+                if (atomic_read(&num_drc_entries) <= max_drc_entries &&
                     time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
                         break;
                 nfsd_reply_cache_free_locked(rp);
@@ -290,13 +290,7 @@ cache_cleaner_func(struct work_struct *unused)
 static unsigned long
 nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
 {
-        unsigned long num;
-
-        spin_lock(&cache_lock);
-        num = num_drc_entries;
-        spin_unlock(&cache_lock);
-
-        return num;
+        return atomic_read(&num_drc_entries);
 }
 
 static unsigned long
@@ -386,11 +380,12 @@ nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
         /* tally hash chain length stats */
         if (entries > longest_chain) {
                 longest_chain = entries;
-                longest_chain_cachesize = num_drc_entries;
+                longest_chain_cachesize = atomic_read(&num_drc_entries);
         } else if (entries == longest_chain) {
                 /* prefer to keep the smallest cachesize possible here */
-                longest_chain_cachesize = min(longest_chain_cachesize,
-                                                num_drc_entries);
+                longest_chain_cachesize = min_t(unsigned int,
+                                longest_chain_cachesize,
+                                atomic_read(&num_drc_entries));
         }
 
         return ret;
@@ -433,7 +428,7 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
         rp = nfsd_reply_cache_alloc();
         spin_lock(&cache_lock);
         if (likely(rp)) {
-                ++num_drc_entries;
+                atomic_inc(&num_drc_entries);
                 drc_mem_usage += sizeof(*rp);
         }
 
@@ -617,7 +612,8 @@ static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
 {
         spin_lock(&cache_lock);
         seq_printf(m, "max entries:           %u\n", max_drc_entries);
-        seq_printf(m, "num entries:           %u\n", num_drc_entries);
+        seq_printf(m, "num entries:           %u\n",
+                        atomic_read(&num_drc_entries));
         seq_printf(m, "hash buckets:          %u\n", 1 << maskbits);
         seq_printf(m, "mem usage:             %u\n", drc_mem_usage);
         seq_printf(m, "cache hits:            %u\n", nfsdstats.rchits);