nfs: modify pg_test interface to return size_t

This is a step toward allowing pg_test to inform the the
coalescing code to reduce the size of requests so they may fit in
whatever scheme the pg_test callback wants to define.

For now, just return the size of the request if there is space, or 0
if there is not. This shouldn't change any behavior as it acts
the same as when the pg_test functions returned bool.

Signed-off-by: Weston Andros Adamson <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/blocklayout/blocklayout.c

···
 		pnfs_generic_pg_init_read(pgio, req);
 }
 
-static bool
+/*
+ * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
+ * of bytes (maximum @req->wb_bytes) that can be coalesced.
+ */
+static size_t
 bl_pg_test_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 		struct nfs_page *req)
 {
 	if (pgio->pg_dreq != NULL &&
 	    !is_aligned_req(req, SECTOR_SIZE))
-		return false;
+		return 0;
 
 	return pnfs_generic_pg_test(pgio, prev, req);
 }
···
 	}
 }
 
-static bool
+/*
+ * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
+ * of bytes (maximum @req->wb_bytes) that can be coalesced.
+ */
+static size_t
 bl_pg_test_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 		 struct nfs_page *req)
 {
 	if (pgio->pg_dreq != NULL &&
 	    !is_aligned_req(req, PAGE_CACHE_SIZE))
-		return false;
+		return 0;
 
 	return pnfs_generic_pg_test(pgio, prev, req);
 }

fs/nfs/nfs4filelayout.c

···
 /*
  * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
  *
- * return true  : coalesce page
- * return false : don't coalesce page
+ * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
+ * of bytes (maximum @req->wb_bytes) that can be coalesced.
  */
-static bool
+static size_t
 filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 		   struct nfs_page *req)
 {
···
 
 	if (!pnfs_generic_pg_test(pgio, prev, req) ||
 	    !nfs_generic_pg_test(pgio, prev, req))
-		return false;
+		return 0;
 
 	p_stripe = (u64)req_offset(prev);
 	r_stripe = (u64)req_offset(req);
···
 	do_div(p_stripe, stripe_unit);
 	do_div(r_stripe, stripe_unit);
 
-	return (p_stripe == r_stripe);
+	if (p_stripe == r_stripe)
+		return req->wb_bytes;
+	return 0;
 }
 
 static void

fs/nfs/objlayout/objio_osd.c

···
 	return 0;
 }
 
-static bool objio_pg_test(struct nfs_pageio_descriptor *pgio,
+/*
+ * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
+ * of bytes (maximum @req->wb_bytes) that can be coalesced.
+ */
+static size_t objio_pg_test(struct nfs_pageio_descriptor *pgio,
 			  struct nfs_page *prev, struct nfs_page *req)
 {
-	if (!pnfs_generic_pg_test(pgio, prev, req))
-		return false;
+	if (!pnfs_generic_pg_test(pgio, prev, req) ||
+	    pgio->pg_count + req->wb_bytes >
+	    (unsigned long)pgio->pg_layout_private)
+		return 0;
 
-	return pgio->pg_count + req->wb_bytes <=
-			(unsigned long)pgio->pg_layout_private;
+	return req->wb_bytes;
 }
 
 static void objio_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)

fs/nfs/pagelist.c

···
 			TASK_UNINTERRUPTIBLE);
 }
 
-bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
+/*
+ * nfs_generic_pg_test - determine if requests can be coalesced
+ * @desc: pointer to descriptor
+ * @prev: previous request in desc, or NULL
+ * @req: this request
+ *
+ * Returns zero if @req can be coalesced into @desc, otherwise it returns
+ * the size of the request.
+ */
+size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
+			   struct nfs_page *prev, struct nfs_page *req)
 {
 	/*
 	 * FIXME: ideally we should be able to coalesce all requests
···
 	if (desc->pg_bsize < PAGE_SIZE)
 		return 0;
 
-	return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
+	if (desc->pg_count + req->wb_bytes <= desc->pg_bsize)
+		return req->wb_bytes;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
 
···
 				      struct nfs_page *req,
 				      struct nfs_pageio_descriptor *pgio)
 {
+	size_t size;
+
 	if (!nfs_match_open_context(req->wb_context, prev->wb_context))
 		return false;
 	if (req->wb_context->dentry->d_inode->i_flock != NULL &&
···
 		return false;
 	if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
 		return false;
-	return pgio->pg_ops->pg_test(pgio, prev, req);
+	size = pgio->pg_ops->pg_test(pgio, prev, req);
+	WARN_ON_ONCE(size && size != req->wb_bytes);
+	return size > 0;
 }
 
 /**

fs/nfs/pnfs.c

···
 }
 EXPORT_SYMBOL_GPL(pnfs_generic_pg_init_write);
 
-bool
+/*
+ * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
+ * of bytes (maximum @req->wb_bytes) that can be coalesced.
+ */
+size_t
 pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 		     struct nfs_page *req)
 {
···
 	 * first byte that lies outside the pnfs_layout_range. FIXME?
 	 *
 	 */
-	return req_offset(req) < end_offset(pgio->pg_lseg->pls_range.offset,
-					 pgio->pg_lseg->pls_range.length);
+	if (req_offset(req) < end_offset(pgio->pg_lseg->pls_range.offset,
+					 pgio->pg_lseg->pls_range.length))
+		return req->wb_bytes;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(pnfs_generic_pg_test);
 

fs/nfs/pnfs.h

···
 void pnfs_generic_pg_init_write(struct nfs_pageio_descriptor *pgio,
 			        struct nfs_page *req, u64 wb_size);
 int pnfs_generic_pg_writepages(struct nfs_pageio_descriptor *desc);
-bool pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev, struct nfs_page *req);
+size_t pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio,
+			    struct nfs_page *prev, struct nfs_page *req);
 void pnfs_set_lo_fail(struct pnfs_layout_segment *lseg);
 struct pnfs_layout_segment *pnfs_layout_process(struct nfs4_layoutget *lgp);
 void pnfs_free_lseg_list(struct list_head *tmp_list);

include/linux/nfs_page.h

···
 struct nfs_pageio_descriptor;
 struct nfs_pageio_ops {
 	void	(*pg_init)(struct nfs_pageio_descriptor *, struct nfs_page *);
-	bool	(*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *, struct nfs_page *);
+	size_t	(*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *,
+			   struct nfs_page *);
 	int	(*pg_doio)(struct nfs_pageio_descriptor *);
 };
 
···
 				   struct nfs_page *);
 extern	void nfs_pageio_complete(struct nfs_pageio_descriptor *desc);
 extern	void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *, pgoff_t);
-extern bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
+extern size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
 				struct nfs_page *prev,
 				struct nfs_page *req);
 extern  int nfs_wait_on_request(struct nfs_page *);