fs/sysv: Change the signature of dir_get_page()

Change the signature of dir_get_page() in order to prepare this function
to the conversion to the use of kmap_local_page(). Change also those call
sites which are required to adjust to the new signature.

Cc: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/sysv/dir.c

@@ -57,13 +57,15 @@ static int sysv_handle_dirsync(struct inode *dir)
 	return err;
 }
 
-static struct page * dir_get_page(struct inode *dir, unsigned long n)
+static void *dir_get_page(struct inode *dir, unsigned long n, struct page **p)
 {
 	struct address_space *mapping = dir->i_mapping;
 	struct page *page = read_mapping_page(mapping, n, NULL);
-	if (!IS_ERR(page))
-		kmap(page);
-	return page;
+	if (IS_ERR(page))
+		return ERR_CAST(page);
+	kmap(page);
+	*p = page;
+	return page_address(page);
 }
 
 static int sysv_readdir(struct file *file, struct dir_context *ctx)
@@ -85,11 +87,11 @@ static int sysv_readdir(struct file *file, struct dir_context *ctx)
 	for ( ; n < npages; n++, offset = 0) {
 		char *kaddr, *limit;
 		struct sysv_dir_entry *de;
-		struct page *page = dir_get_page(inode, n);
+		struct page *page;
 
-		if (IS_ERR(page))
+		kaddr = dir_get_page(inode, n, &page);
+		if (IS_ERR(kaddr))
 			continue;
-		kaddr = (char *)page_address(page);
 		de = (struct sysv_dir_entry *)(kaddr+offset);
 		limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
 		for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
@@ -147,11 +149,10 @@ struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_
 	n = start;
 
 	do {
-		char *kaddr;
-		page = dir_get_page(dir, n);
-		if (!IS_ERR(page)) {
-			kaddr = (char*)page_address(page);
-			de = (struct sysv_dir_entry *) kaddr;
+		char *kaddr = dir_get_page(dir, n, &page);
+
+		if (!IS_ERR(kaddr)) {
+			de = (struct sysv_dir_entry *)kaddr;
 			kaddr += PAGE_SIZE - SYSV_DIRSIZE;
 			for ( ; (char *) de <= kaddr ; de++) {
 				if (!de->inode)
@@ -190,11 +191,9 @@ int sysv_add_link(struct dentry *dentry, struct inode *inode)
 
 	/* We take care of directory expansion in the same loop */
 	for (n = 0; n <= npages; n++) {
-		page = dir_get_page(dir, n);
-		err = PTR_ERR(page);
-		if (IS_ERR(page))
-			goto out;
-		kaddr = (char*)page_address(page);
+		kaddr = dir_get_page(dir, n, &page);
+		if (IS_ERR(kaddr))
+			return PTR_ERR(kaddr);
 		de = (struct sysv_dir_entry *)kaddr;
 		kaddr += PAGE_SIZE - SYSV_DIRSIZE;
 		while ((char *)de <= kaddr) {
@@ -225,7 +224,6 @@ int sysv_add_link(struct dentry *dentry, struct inode *inode)
 	err = sysv_handle_dirsync(dir);
 out_page:
 	dir_put_page(page);
-out:
 	return err;
 out_unlock:
 	unlock_page(page);
@@ -295,12 +293,11 @@ int sysv_empty_dir(struct inode * inode)
 	for (i = 0; i < npages; i++) {
 		char *kaddr;
 		struct sysv_dir_entry * de;
-		page = dir_get_page(inode, i);
 
-		if (IS_ERR(page))
+		kaddr = dir_get_page(inode, i, &page);
+		if (IS_ERR(kaddr))
 			continue;
 
-		kaddr = (char *)page_address(page);
 		de = (struct sysv_dir_entry *)kaddr;
 		kaddr += PAGE_SIZE-SYSV_DIRSIZE;
 
@@ -347,16 +344,14 @@ void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
 	sysv_handle_dirsync(inode);
 }
 
-struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
+struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct page **p)
 {
-	struct page *page = dir_get_page(dir, 0);
-	struct sysv_dir_entry *de = NULL;
+	struct sysv_dir_entry *de = dir_get_page(dir, 0, p);
 
-	if (!IS_ERR(page)) {
-		de = (struct sysv_dir_entry*) page_address(page) + 1;
-		*p = page;
-	}
-	return de;
+	if (IS_ERR(de))
+		return NULL;
+	/* ".." is the second directory entry */
+	return de + 1;
 }
 
 ino_t sysv_inode_by_name(struct dentry *dentry)