[PATCH 1/3] SUNRPC add deferral processing callbacks

[andros@netapp.com]

From: Andy Adamson <andros@netapp.com>

For EOS, NFSD compound RPC deferred processing should restart operation which
caused the deferral.

Add a callback and a defer_data pointer in svc_rqst to enable svc_defer to
save partial result state in the deferral request.

Add page pointer storage to svc_deferred_req to cache the pages holding the
partially processed request.

Add callbacks and a defer_data pointer in svc_deferred_request to enable
svc_deferred_recv to restore and release the partial result state.

Signed-off-by: Andy Adamson<andros-HgOvQuBEEgQAvxtiuMwx3w@public.gmane.org>
---
 include/linux/sunrpc/svc.h |   10 ++++++++++
 net/sunrpc/svc_xprt.c      |   20 +++++++++++++++-----
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index dc69068..46a4097 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -215,6 +215,9 @@ struct svc_rqst {
 	struct svc_cred		rq_cred;	/* auth info */
 	void *			rq_xprt_ctxt;	/* transport specific context ptr */
 	struct svc_deferred_req*rq_deferred;	/* deferred request we are replaying */
+	/* callback to save deferred request state */
+	void (*rq_save_state)(struct svc_rqst *, struct svc_deferred_req *);
+	void			*rq_defer_data; /* defer state data to save */
 
 	size_t			rq_xprt_hlen;	/* xprt header len */
 	struct xdr_buf		rq_arg;
@@ -323,6 +326,13 @@ struct svc_deferred_req {
 	union svc_addr_u	daddr;	/* where reply must come from */
 	struct cache_deferred_req handle;
 	size_t			xprt_hlen;
+	/* callbacks to restore and release deferred request state
+	 * set in rq_save_state */
+	void (*restore_state)(struct svc_rqst *, struct svc_deferred_req *);
+	void (*release_state)(struct svc_deferred_req *);
+	void			*defer_data; /* defer state data */
+	struct page		*respages[RPCSVC_MAXPAGES];
+	short			resused;
 	int			argslen;
 	__be32			args[0];
 };
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index e46c825..531b325 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -876,6 +876,8 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
 	struct svc_xprt *xprt = dr->xprt;
 
 	if (too_many) {
+		if (dr->release_state)
+			dr->release_state(dr);
 		svc_xprt_put(xprt);
 		kfree(dr);
 		return;
@@ -902,10 +904,10 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
 static struct cache_deferred_req *svc_defer(struct cache_req *req)
 {
 	struct svc_rqst *rqstp = container_of(req, struct svc_rqst, rq_chandle);
-	struct svc_deferred_req *dr;
+	struct svc_deferred_req *dr = NULL;
 
 	if (rqstp->rq_arg.page_len)
-		return NULL; /* if more than a page, give up FIXME */
+		goto out; /* if more than a page, give up FIXME */
 	if (rqstp->rq_deferred) {
 		dr = rqstp->rq_deferred;
 		rqstp->rq_deferred = NULL;
@@ -914,9 +916,9 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
 		size_t size;
 		/* FIXME maybe discard if size too large */
 		size = sizeof(struct svc_deferred_req) + rqstp->rq_arg.len;
-		dr = kmalloc(size, GFP_KERNEL);
+		dr = kzalloc(size, GFP_KERNEL);
 		if (dr == NULL)
-			return NULL;
+			goto out;
 
 		dr->handle.owner = rqstp->rq_server;
 		dr->prot = rqstp->rq_prot;
@@ -935,7 +937,13 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
 	dr->xprt = rqstp->rq_xprt;
 
 	dr->handle.revisit = svc_revisit;
-	return &dr->handle;
+	if (rqstp->rq_save_state)
+		rqstp->rq_save_state(rqstp, dr);
+out:
+	rqstp->rq_defer_data = NULL;
+	rqstp->rq_save_state = NULL;
+
+	return dr ? &dr->handle: NULL;
 }
 
 /*
@@ -959,6 +967,8 @@ static int svc_deferred_recv(struct svc_rqst *rqstp)
 	rqstp->rq_xprt_hlen   = dr->xprt_hlen;
 	rqstp->rq_daddr       = dr->daddr;
 	rqstp->rq_respages    = rqstp->rq_pages;
+	if (dr->restore_state)
+		dr->restore_state(rqstp, dr);
 	return (dr->argslen<<2) - dr->xprt_hlen;
 }
 
-- 
1.5.4.3