minixfs: 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.

Essentially a copy of the corresponding fs/sysv commit by
Fabio M. De Francesco <fmdefrancesco@gmail.com>

Reviewed-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

fs/minix/dir.c

@@ -70,13 +70,15 @@ static int minix_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 inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
@@ -104,11 +106,11 @@ static int minix_readdir(struct file *file, struct dir_context *ctx)
 
 	for ( ; n < npages; n++, offset = 0) {
 		char *p, *kaddr, *limit;
-		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);
 		p = kaddr+offset;
 		limit = kaddr + minix_last_byte(inode, n) - chunk_size;
 		for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
@@ -173,11 +175,10 @@ minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page)
 	for (n = 0; n < npages; n++) {
 		char *kaddr, *limit;
 
-		page = dir_get_page(dir, n);
-		if (IS_ERR(page))
+		kaddr = dir_get_page(dir, n, &page);
+		if (IS_ERR(kaddr))
 			continue;
 
-		kaddr = (char*)page_address(page);
 		limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 			if (sbi->s_version == MINIX_V3) {
@@ -229,12 +230,10 @@ int minix_add_link(struct dentry *dentry, struct inode *inode)
 	for (n = 0; n <= npages; n++) {
 		char *limit, *dir_end;
 
-		page = dir_get_page(dir, n);
-		err = PTR_ERR(page);
-		if (IS_ERR(page))
-			goto out;
+		kaddr = dir_get_page(dir, n, &page);
+		if (IS_ERR(kaddr))
+			return PTR_ERR(kaddr);
 		lock_page(page);
-		kaddr = (char*)page_address(page);
 		dir_end = kaddr + minix_last_byte(dir, n);
 		limit = kaddr + PAGE_SIZE - sbi->s_dirsize;
 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
@@ -286,7 +285,6 @@ int minix_add_link(struct dentry *dentry, struct inode *inode)
 	err = minix_handle_dirsync(dir);
 out_put:
 	dir_put_page(page);
-out:
 	return err;
 out_unlock:
 	unlock_page(page);
@@ -375,11 +373,10 @@ int minix_empty_dir(struct inode * inode)
 	for (i = 0; i < npages; i++) {
 		char *p, *kaddr, *limit;
 
-		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);
 		limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 			if (sbi->s_version == MINIX_V3) {
@@ -441,15 +438,12 @@ int minix_set_link(struct minix_dir_entry *de, struct page *page,
 
 struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
 {
-	struct page *page = dir_get_page(dir, 0);
 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
-	struct minix_dir_entry *de = NULL;
+	struct minix_dir_entry *de = dir_get_page(dir, 0, p);
 
-	if (!IS_ERR(page)) {
-		de = minix_next_entry(page_address(page), sbi);
-		*p = page;
-	}
-	return de;
+	if (!IS_ERR(de))
+		return minix_next_entry(de, sbi);
+	return NULL;
 }
 
 ino_t minix_inode_by_name(struct dentry *dentry)