[PATCH] knfsd: Replace two page lists in struct svc_rqst with one

We are planning to increase RPCSVC_MAXPAGES from about 8 to about 256.  This
means we need to be a bit careful about arrays of size RPCSVC_MAXPAGES.

struct svc_rqst contains two such arrays.  However the there are never more
that RPCSVC_MAXPAGES pages in the two arrays together, so only one array is
needed.

The two arrays are for the pages holding the request, and the pages holding
the reply.  Instead of two arrays, we can simply keep an index into where the
first reply page is.

This patch also removes a number of small inline functions that probably
server to obscure what is going on rather than clarify it, and opencode the
needed functionality.

Also remove the 'rq_restailpage' variable as it is *always* 0.  i.e.  if the
response 'xdr' structure has a non-empty tail it is always in the same pages
as the head.

 check counters are initilised and incr properly
 check for consistant usage of ++ etc
 maybe extra some inlines for common approach
 general review

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: Magnus Maatta <novell@kiruna.se>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 59 deletions

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 4ebcdf91f3b3..3669e91c43b8 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -170,7 +170,6 @@ static inline void svc_putu32(struct kvec *iov, __be32 val)
 /*
  * The context of a single thread, including the request currently being
  * processed.
- * NOTE: First two items must be prev/next.
  */
 struct svc_rqst {
 	struct list_head	rq_list;	/* idle list */
@@ -189,12 +188,9 @@ struct svc_rqst {
 
 	struct xdr_buf		rq_arg;
 	struct xdr_buf		rq_res;
-	struct page *		rq_argpages[RPCSVC_MAXPAGES];
-	struct page *		rq_respages[RPCSVC_MAXPAGES];
-	int			rq_restailpage;
-	short			rq_argused;	/* pages used for argument */
-	short			rq_arghi;	/* pages available in argument page list */
-	short			rq_resused;	/* pages used for result */
+	struct page *		rq_pages[RPCSVC_MAXPAGES];
+	struct page *		*rq_respages;	/* points into rq_pages */
+	int			rq_resused;	/* number of pages used for result */
 
 	__be32			rq_xid;		/* transmission id */
 	u32			rq_prog;	/* program number */
@@ -255,63 +251,18 @@ xdr_ressize_check(struct svc_rqst *rqstp, __be32 *p)
 	return vec->iov_len <= PAGE_SIZE;
 }
 
-static inline struct page *
-svc_take_res_page(struct svc_rqst *rqstp)
+static inline void svc_free_res_pages(struct svc_rqst *rqstp)
 {
-	if (rqstp->rq_arghi <= rqstp->rq_argused)
-		return NULL;
-	rqstp->rq_arghi--;
-	rqstp->rq_respages[rqstp->rq_resused] =
-		rqstp->rq_argpages[rqstp->rq_arghi];
-	return rqstp->rq_respages[rqstp->rq_resused++];
-}
-
-static inline void svc_take_page(struct svc_rqst *rqstp)
-{
-	if (rqstp->rq_arghi <= rqstp->rq_argused) {
-		WARN_ON(1);
-		return;
-	}
-	rqstp->rq_arghi--;
-	rqstp->rq_respages[rqstp->rq_resused] =
-		rqstp->rq_argpages[rqstp->rq_arghi];
-	rqstp->rq_resused++;
-}
-
-static inline void svc_pushback_allpages(struct svc_rqst *rqstp)
-{
-        while (rqstp->rq_resused) {
-		if (rqstp->rq_respages[--rqstp->rq_resused] == NULL)
-			continue;
-		rqstp->rq_argpages[rqstp->rq_arghi++] =
-			rqstp->rq_respages[rqstp->rq_resused];
-		rqstp->rq_respages[rqstp->rq_resused] = NULL;
-	}
-}
-
-static inline void svc_pushback_unused_pages(struct svc_rqst *rqstp)
-{
-	while (rqstp->rq_resused &&
-	       rqstp->rq_res.pages != &rqstp->rq_respages[rqstp->rq_resused]) {
-
-		if (rqstp->rq_respages[--rqstp->rq_resused] != NULL) {
-			rqstp->rq_argpages[rqstp->rq_arghi++] =
-				rqstp->rq_respages[rqstp->rq_resused];
-			rqstp->rq_respages[rqstp->rq_resused] = NULL;
+	while (rqstp->rq_resused) {
+		struct page **pp = (rqstp->rq_respages +
+				    --rqstp->rq_resused);
+		if (*pp) {
+			put_page(*pp);
+			*pp = NULL;
 		}
 	}
 }
 
-static inline void svc_free_allpages(struct svc_rqst *rqstp)
-{
-        while (rqstp->rq_resused) {
-		if (rqstp->rq_respages[--rqstp->rq_resused] == NULL)
-			continue;
-		put_page(rqstp->rq_respages[rqstp->rq_resused]);
-		rqstp->rq_respages[rqstp->rq_resused] = NULL;
-	}
-}
-
 struct svc_deferred_req {
 	u32			prot;	/* protocol (UDP or TCP) */
 	struct sockaddr_in	addr;