From d8a5ad75cc4d577987964e37a4c43b1c648c201e Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Mon, 2 Apr 2007 18:48:28 -0400
Subject: NFS: Cleanup the coalescing code

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---
 fs/nfs/pagelist.c | 117 +++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 85 insertions(+), 32 deletions(-)

(limited to 'fs/nfs/pagelist.c')

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index ca4b1d4ff42..7017eb0e0bc 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -223,48 +223,101 @@ out:
 }
 
 /**
- * nfs_coalesce_requests - Split coalesced requests out from a list.
+ * nfs_pageio_init - initialise a page io descriptor
+ * @desc: pointer to descriptor
+ * @iosize: io block size
+ */
+void nfs_pageio_init(struct nfs_pageio_descriptor *desc, unsigned int bsize)
+{
+	INIT_LIST_HEAD(&desc->pg_list);
+	desc->pg_count = 0;
+	desc->pg_bsize = bsize;
+	desc->pg_base = 0;
+}
+
+/**
+ * nfs_can_coalesce_requests - test two requests for compatibility
+ * @prev: pointer to nfs_page
+ * @req: pointer to nfs_page
+ *
+ * The nfs_page structures 'prev' and 'req' are compared to ensure that the
+ * page data area they describe is contiguous, and that their RPC
+ * credentials, NFSv4 open state, and lockowners are the same.
+ *
+ * Return 'true' if this is the case, else return 'false'.
+ */
+static int nfs_can_coalesce_requests(struct nfs_page *prev,
+				     struct nfs_page *req)
+{
+	if (req->wb_context->cred != prev->wb_context->cred)
+		return 0;
+	if (req->wb_context->lockowner != prev->wb_context->lockowner)
+		return 0;
+	if (req->wb_context->state != prev->wb_context->state)
+		return 0;
+	if (req->wb_index != (prev->wb_index + 1))
+		return 0;
+	if (req->wb_pgbase != 0)
+		return 0;
+	if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
+		return 0;
+	return 1;
+}
+
+/**
+ * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
+ * @desc: destination io descriptor
+ * @req: request
+ *
+ * Returns true if the request 'req' was successfully coalesced into the
+ * existing list of pages 'desc'.
+ */
+static int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
+				  struct nfs_page *req)
+{
+	size_t newlen = req->wb_bytes;
+
+	if (desc->pg_count != 0) {
+		struct nfs_page *prev;
+
+		/*
+		 * FIXME: ideally we should be able to coalesce all requests
+		 * that are not block boundary aligned, but currently this
+		 * is problematic for the case of bsize < PAGE_CACHE_SIZE,
+		 * since nfs_flush_multi and nfs_pagein_multi assume you
+		 * can have only one struct nfs_page.
+		 */
+		newlen += desc->pg_count;
+		if (desc->pg_base + newlen > desc->pg_bsize)
+			return 0;
+		prev = nfs_list_entry(desc->pg_list.prev);
+		if (!nfs_can_coalesce_requests(prev, req))
+			return 0;
+	} else
+		desc->pg_base = req->wb_pgbase;
+	nfs_list_remove_request(req);
+	nfs_list_add_request(req, &desc->pg_list);
+	desc->pg_count = newlen;
+	return 1;
+}
+
+/**
+ * nfs_pageio_add_list - Split coalesced requests out from a list.
+ * @desc: destination io descriptor
  * @head: source list
- * @dst: destination list
- * @nmax: maximum number of requests to coalesce
  *
  * Moves a maximum of 'nmax' elements from one list to another.
  * The elements are checked to ensure that they form a contiguous set
  * of pages, and that the RPC credentials are the same.
  */
-int
-nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
-		      unsigned int nmax)
+void nfs_pageio_add_list(struct nfs_pageio_descriptor *desc,
+			 struct list_head *head)
 {
-	struct nfs_page		*req = NULL;
-	unsigned int		npages = 0;
-
 	while (!list_empty(head)) {
-		struct nfs_page	*prev = req;
-
-		req = nfs_list_entry(head->next);
-		if (prev) {
-			if (req->wb_context->cred != prev->wb_context->cred)
-				break;
-			if (req->wb_context->lockowner != prev->wb_context->lockowner)
-				break;
-			if (req->wb_context->state != prev->wb_context->state)
-				break;
-			if (req->wb_index != (prev->wb_index + 1))
-				break;
-
-			if (req->wb_pgbase != 0)
-				break;
-		}
-		nfs_list_remove_request(req);
-		nfs_list_add_request(req, dst);
-		npages++;
-		if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
-			break;
-		if (npages >= nmax)
+		struct nfs_page *req = nfs_list_entry(head->next);
+		if (!nfs_pageio_add_request(desc, req))
 			break;
 	}
-	return npages;
 }
 
 #define NFS_SCAN_MAXENTRIES 16
-- 
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