NFS: Clean up nfs_readpage() and nfs_readpages()

In prep for the new fscache netfs API, refactor nfs_readpage()
and nfs_readpages() for future patches.  No functional change.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/read.c

@@ -314,7 +314,7 @@ int nfs_readpage(struct file *file, struct page *page)
 {
 	struct nfs_open_context *ctx;
 	struct inode *inode = page_file_mapping(page)->host;
-	int		error;
+	int ret;
 
 	dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 		page, PAGE_SIZE, page_index(page));
@@ -328,18 +328,18 @@ int nfs_readpage(struct file *file, struct page *page)
 	 * be any new pending writes generated at this point
 	 * for this page (other pages can be written to).
 	 */
-	error = nfs_wb_page(inode, page);
-	if (error)
+	ret = nfs_wb_page(inode, page);
+	if (ret)
 		goto out_unlock;
 	if (PageUptodate(page))
 		goto out_unlock;
 
-	error = -ESTALE;
+	ret = -ESTALE;
 	if (NFS_STALE(inode))
 		goto out_unlock;
 
 	if (file == NULL) {
-		error = -EBADF;
+		ret = -EBADF;
 		ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 		if (ctx == NULL)
 			goto out_unlock;
@@ -347,24 +347,24 @@ int nfs_readpage(struct file *file, struct page *page)
 		ctx = get_nfs_open_context(nfs_file_open_context(file));
 
 	if (!IS_SYNC(inode)) {
-		error = nfs_readpage_from_fscache(ctx, inode, page);
-		if (error == 0)
+		ret = nfs_readpage_from_fscache(ctx, inode, page);
+		if (ret == 0)
 			goto out;
 	}
 
 	xchg(&ctx->error, 0);
-	error = nfs_readpage_async(ctx, inode, page);
-	if (!error) {
-		error = wait_on_page_locked_killable(page);
-		if (!PageUptodate(page) && !error)
-			error = xchg(&ctx->error, 0);
+	ret = nfs_readpage_async(ctx, inode, page);
+	if (!ret) {
+		ret = wait_on_page_locked_killable(page);
+		if (!PageUptodate(page) && !ret)
+			ret = xchg(&ctx->error, 0);
 	}
 out:
 	put_nfs_open_context(ctx);
-	return error;
+	return ret;
 out_unlock:
 	unlock_page(page);
-	return error;
+	return ret;
 }
 
 struct nfs_readdesc {
@@ -404,17 +404,15 @@ readpage_async_filler(void *data, struct page *page)
 	return error;
 }
 
-int nfs_readpages(struct file *filp, struct address_space *mapping,
+int nfs_readpages(struct file *file, struct address_space *mapping,
 		struct list_head *pages, unsigned nr_pages)
 {
 	struct nfs_pageio_descriptor pgio;
 	struct nfs_pgio_mirror *pgm;
-	struct nfs_readdesc desc = {
-		.pgio = &pgio,
-	};
+	struct nfs_readdesc desc;
 	struct inode *inode = mapping->host;
 	unsigned long npages;
-	int ret = -ESTALE;
+	int ret;
 
 	dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
 			inode->i_sb->s_id,
@@ -422,15 +420,17 @@ int nfs_readpages(struct file *filp, struct address_space *mapping,
 			nr_pages);
 	nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 
+	ret = -ESTALE;
 	if (NFS_STALE(inode))
 		goto out;
 
-	if (filp == NULL) {
+	if (file == NULL) {
+		ret = -EBADF;
 		desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 		if (desc.ctx == NULL)
-			return -EBADF;
+			goto out;
 	} else
-		desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
+		desc.ctx = get_nfs_open_context(nfs_file_open_context(file));
 
 	/* attempt to read as many of the pages as possible from the cache
 	 * - this returns -ENOBUFS immediately if the cookie is negative
@@ -440,6 +440,7 @@ int nfs_readpages(struct file *filp, struct address_space *mapping,
 	if (ret == 0)
 		goto read_complete; /* all pages were read */
 
+	desc.pgio = &pgio;
 	nfs_pageio_init_read(&pgio, inode, false,
 			     &nfs_async_read_completion_ops);