nilfs2: return the mapped address from nilfs_get_page()

In prepartion for switching from kmap() to kmap_local(), return the kmap
address from nilfs_get_page() instead of having the caller look up
page_address().

[konishi.ryusuke: fixed a missing blank line after declaration]
Link: https://lkml.kernel.org/r/20231127143036.2425-7-konishi.ryusuke@gmail.comSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/dir.c

@@ -180,19 +180,24 @@ static bool nilfs_check_page(struct page *page)
 	return false;
 }
 
-static struct page *nilfs_get_page(struct inode *dir, unsigned long n)
+static void *nilfs_get_page(struct inode *dir, unsigned long n,
+		struct page **pagep)
 {
 	struct address_space *mapping = dir->i_mapping;
 	struct page *page = read_mapping_page(mapping, n, NULL);
+	void *kaddr;
 
-	if (!IS_ERR(page)) {
-		kmap(page);
-		if (unlikely(!PageChecked(page))) {
-			if (!nilfs_check_page(page))
-				goto fail;
-		}
+	if (IS_ERR(page))
+		return page;
+
+	kaddr = kmap(page);
+	if (unlikely(!PageChecked(page))) {
+		if (!nilfs_check_page(page))
+			goto fail;
 	}
-	return page;
+
+	*pagep = page;
+	return kaddr;
 
 fail:
 	nilfs_put_page(page);
@@ -269,14 +274,14 @@ static int nilfs_readdir(struct file *file, struct dir_context *ctx)
 	for ( ; n < npages; n++, offset = 0) {
 		char *kaddr, *limit;
 		struct nilfs_dir_entry *de;
-		struct page *page = nilfs_get_page(inode, n);
+		struct page *page;
 
-		if (IS_ERR(page)) {
+		kaddr = nilfs_get_page(inode, n, &page);
+		if (IS_ERR(kaddr)) {
 			nilfs_error(sb, "bad page in #%lu", inode->i_ino);
 			ctx->pos += PAGE_SIZE - offset;
 			return -EIO;
 		}
-		kaddr = page_address(page);
 		de = (struct nilfs_dir_entry *)(kaddr + offset);
 		limit = kaddr + nilfs_last_byte(inode, n) -
 			NILFS_DIR_REC_LEN(1);
@@ -339,11 +344,9 @@ nilfs_find_entry(struct inode *dir, const struct qstr *qstr,
 		start = 0;
 	n = start;
 	do {
-		char *kaddr;
+		char *kaddr = nilfs_get_page(dir, n, &page);
 
-		page = nilfs_get_page(dir, n);
-		if (!IS_ERR(page)) {
-			kaddr = page_address(page);
+		if (!IS_ERR(kaddr)) {
 			de = (struct nilfs_dir_entry *)kaddr;
 			kaddr += nilfs_last_byte(dir, n) - reclen;
 			while ((char *) de <= kaddr) {
@@ -381,15 +384,11 @@ nilfs_find_entry(struct inode *dir, const struct qstr *qstr,
 
 struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
 {
-	struct page *page = nilfs_get_page(dir, 0);
-	struct nilfs_dir_entry *de = NULL;
+	struct nilfs_dir_entry *de = nilfs_get_page(dir, 0, p);
 
-	if (!IS_ERR(page)) {
-		de = nilfs_next_entry(
-			(struct nilfs_dir_entry *)page_address(page));
-		*p = page;
-	}
-	return de;
+	if (IS_ERR(de))
+		return NULL;
+	return nilfs_next_entry(de);
 }
 
 ino_t nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr)
@@ -451,12 +450,11 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 	for (n = 0; n <= npages; n++) {
 		char *dir_end;
 
-		page = nilfs_get_page(dir, n);
-		err = PTR_ERR(page);
-		if (IS_ERR(page))
+		kaddr = nilfs_get_page(dir, n, &page);
+		err = PTR_ERR(kaddr);
+		if (IS_ERR(kaddr))
 			goto out;
 		lock_page(page);
-		kaddr = page_address(page);
 		dir_end = kaddr + nilfs_last_byte(dir, n);
 		de = (struct nilfs_dir_entry *)kaddr;
 		kaddr += PAGE_SIZE - reclen;
@@ -618,11 +616,10 @@ int nilfs_empty_dir(struct inode *inode)
 		char *kaddr;
 		struct nilfs_dir_entry *de;
 
-		page = nilfs_get_page(inode, i);
-		if (IS_ERR(page))
+		kaddr = nilfs_get_page(inode, i, &page);
+		if (IS_ERR(kaddr))
 			continue;
 
-		kaddr = page_address(page);
 		de = (struct nilfs_dir_entry *)kaddr;
 		kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);