NFS: Cleanup the coalescing code

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

3 files changed, 103 insertions, 49 deletions

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index ca4b1d4ff42b..7017eb0e0bc8 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
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 6ab4d5a9edf2..97f0f42e136d 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -328,24 +328,26 @@ out_bad:
 }
 
 static int
-nfs_pagein_list(struct list_head *head, int rpages)
+nfs_pagein_list(struct list_head *head, unsigned int rsize)
 {
-        LIST_HEAD(one_request);
-        struct nfs_page         *req;
-        int                     error = 0;
-        unsigned int            pages = 0;
+        struct nfs_pageio_descriptor desc;
+        struct nfs_page *req;
+        unsigned int pages = 0;
+        int error = 0;
 
         while (!list_empty(head)) {
-                pages += nfs_coalesce_requests(head, &one_request, rpages);
-                req = nfs_list_entry(one_request.next);
-                error = nfs_pagein_one(&one_request, req->wb_context->dentry->d_inode);
+                nfs_pageio_init(&desc, rsize);
+                nfs_pageio_add_list(&desc, head);
+                req = nfs_list_entry(desc.pg_list.next);
+                error = nfs_pagein_one(&desc.pg_list, req->wb_context->dentry->d_inode);
                 if (error < 0)
                         break;
+                pages += (desc.pg_count + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
         }
-        if (error >= 0)
-                return pages;
 
         nfs_async_read_error(head);
+        if (error >= 0)
+                return pages;
         return error;
 }
 
@@ -595,7 +597,7 @@ int nfs_readpages(struct file *filp, struct address_space *mapping,
                                 filp->private_data);
         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
         if (!list_empty(&head)) {
-                int err = nfs_pagein_list(&head, server->rpages);
+                int err = nfs_pagein_list(&head, server->rsize);
                 if (!ret)
                         nfs_add_stats(inode, NFSIOS_READPAGES, err);
                         ret = err;
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index dbad89c8e427..b03ec1ba4d75 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -945,9 +945,8 @@ static int nfs_flush_one(struct inode *inode, struct list_head *head, int how)
 
 static int nfs_flush_list(struct inode *inode, struct list_head *head, int npages, int how)
 {
-        LIST_HEAD(one_request);
+        struct nfs_pageio_descriptor desc;
         int (*flush_one)(struct inode *, struct list_head *, int);
-        struct nfs_page *req;
         int wpages = NFS_SERVER(inode)->wpages;
         int wsize = NFS_SERVER(inode)->wsize;
         int error;
@@ -961,16 +960,16 @@ static int nfs_flush_list(struct inode *inode, struct list_head *head, int npage
                 how |= FLUSH_STABLE;
 
         do {
-                nfs_coalesce_requests(head, &one_request, wpages);
-                req = nfs_list_entry(one_request.next);
-                error = flush_one(inode, &one_request, how);
+                nfs_pageio_init(&desc, wsize);
+                nfs_pageio_add_list(&desc, head);
+                error = flush_one(inode, &desc.pg_list, how);
                 if (error < 0)
                         goto out_err;
         } while (!list_empty(head));
         return 0;
 out_err:
         while (!list_empty(head)) {
-                req = nfs_list_entry(head->next);
+                struct nfs_page *req = nfs_list_entry(head->next);
                 nfs_list_remove_request(req);
                 nfs_redirty_request(req);
                 nfs_end_page_writeback(req->wb_page);