nfsd: break out comparator into separate function

Break out the function that compares the rqstp and checksum against a
reply cache entry. While we're at it, track the efficacy of the checksum
over the NFS data by tracking the cases where we would have incorrectly
matched a DRC entry if we had not tracked it or the length.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 35 insertions, 11 deletions

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index c61391e8e09d..48f5ef944234 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -23,10 +23,22 @@
 static struct hlist_head *      cache_hash;
 static struct list_head         lru_head;
 static struct kmem_cache        *drc_slab;
-static unsigned int             num_drc_entries;
+
+/* max number of entries allowed in the cache */
 static unsigned int             max_drc_entries;
 
 /*
+ * Stats and other tracking of on the duplicate reply cache. All of these and
+ * the "rc" fields in nfsdstats are protected by the cache_lock
+ */
+
+/* total number of entries */
+static unsigned int             num_drc_entries;
+
+/* cache misses due only to checksum comparison failures */
+static unsigned int             payload_misses;
+
+/*
  * Calculate the hash index from an XID.
  */
 static inline u32 request_hash(u32 xid)
@@ -273,6 +285,26 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
         return csum;
 }
 
+static bool
+nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
+{
+        /* Check RPC header info first */
+        if (rqstp->rq_xid != rp->c_xid || rqstp->rq_proc != rp->c_proc ||
+            rqstp->rq_prot != rp->c_prot || rqstp->rq_vers != rp->c_vers ||
+            rqstp->rq_arg.len != rp->c_len ||
+            !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
+            rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
+                return false;
+
+        /* compare checksum of NFS data */
+        if (csum != rp->c_csum) {
+                ++payload_misses;
+                return false;
+        }
+
+        return true;
+}
+
 /*
  * Search the request hash for an entry that matches the given rqstp.
  * Must be called with cache_lock held. Returns the found entry or
@@ -283,18 +315,10 @@ nfsd_cache_search(struct svc_rqst *rqstp, __wsum csum)
 {
         struct svc_cacherep     *rp;
         struct hlist_head       *rh;
-        __be32                  xid = rqstp->rq_xid;
-        u32                     proto =  rqstp->rq_prot,
-                                vers = rqstp->rq_vers,
-                                proc = rqstp->rq_proc;
 
-        rh = &cache_hash[request_hash(xid)];
+        rh = &cache_hash[request_hash(rqstp->rq_xid)];
         hlist_for_each_entry(rp, rh, c_hash) {
-                if (xid == rp->c_xid && proc == rp->c_proc &&
-                    proto == rp->c_prot && vers == rp->c_vers &&
-                    rqstp->rq_arg.len == rp->c_len && csum == rp->c_csum &&
-                    rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) &&
-                    rpc_get_port(svc_addr(rqstp)) == rpc_get_port((struct sockaddr *)&rp->c_addr))
+                if (nfsd_cache_match(rqstp, csum, rp))
                         return rp;
         }
         return NULL;