fs/ext2: Replace kmap() with kmap_local_page()

The k[un]map() calls in ext2_[get|put]_page() are localized to a single
thread.  kmap_local_page() is more efficient.

Replace the kmap/kunmap calls with kmap_local_page()/kunmap_local().
kunmap_local() requires the mapping address so return that address from
ext2_get_page() to be used in ext2_put_page().  This works well because
many of the callers need the address anyway so it is not bad to return
it along with the page.

In addition, kmap_local_page()/kunmap_local() require strict nesting
rules to be followed.

Document the new nesting requirements of ext2_get_page() and
ext2_put_page() as well as the relationship between ext2_get_page(),
ext2_find_entry(), and ext2_dotdot().

Adjust one ext2_put_page() call site in ext2_rename() to ensure the new
nesting requirements are met.

Finally, adjust code style for checkpatch.

To: Jan Kara <jack@suse.com>
Link: https://lore.kernel.org/r/20210329065402.3297092-3-ira.weiny@intel.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 21 insertions, 14 deletions

diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 7af9ab3f975e..c45e175bea9c 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -281,20 +281,21 @@ static int ext2_unlink(struct inode * dir, struct dentry *dentry)
 	struct inode * inode = d_inode(dentry);
 	struct ext2_dir_entry_2 * de;
 	struct page * page;
+	void *page_addr;
 	int err;
 
 	err = dquot_initialize(dir);
 	if (err)
 		goto out;
 
-	de = ext2_find_entry(dir, &dentry->d_name, &page);
+	de = ext2_find_entry(dir, &dentry->d_name, &page, &page_addr);
 	if (IS_ERR(de)) {
 		err = PTR_ERR(de);
 		goto out;
 	}
 
 	err = ext2_delete_entry (de, page);
-	ext2_put_page(page);
+	ext2_put_page(page, page_addr);
 	if (err)
 		goto out;
 
@@ -329,8 +330,10 @@ static int ext2_rename (struct user_namespace * mnt_userns,
 	struct inode * old_inode = d_inode(old_dentry);
 	struct inode * new_inode = d_inode(new_dentry);
 	struct page * dir_page = NULL;
+	void *dir_page_addr;
 	struct ext2_dir_entry_2 * dir_de = NULL;
 	struct page * old_page;
+	void *old_page_addr;
 	struct ext2_dir_entry_2 * old_de;
 	int err;
 
@@ -345,7 +348,8 @@ static int ext2_rename (struct user_namespace * mnt_userns,
 	if (err)
 		goto out;
 
-	old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page);
+	old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page,
+				 &old_page_addr);
 	if (IS_ERR(old_de)) {
 		err = PTR_ERR(old_de);
 		goto out;
@@ -353,12 +357,13 @@ static int ext2_rename (struct user_namespace * mnt_userns,
 
 	if (S_ISDIR(old_inode->i_mode)) {
 		err = -EIO;
-		dir_de = ext2_dotdot(old_inode, &dir_page);
+		dir_de = ext2_dotdot(old_inode, &dir_page, &dir_page_addr);
 		if (!dir_de)
 			goto out_old;
 	}
 
 	if (new_inode) {
+		void *page_addr;
 		struct page *new_page;
 		struct ext2_dir_entry_2 *new_de;
 
@@ -366,13 +371,14 @@ static int ext2_rename (struct user_namespace * mnt_userns,
 		if (dir_de && !ext2_empty_dir (new_inode))
 			goto out_dir;
 
-		new_de = ext2_find_entry(new_dir, &new_dentry->d_name, &new_page);
+		new_de = ext2_find_entry(new_dir, &new_dentry->d_name,
+					 &new_page, &page_addr);
 		if (IS_ERR(new_de)) {
 			err = PTR_ERR(new_de);
 			goto out_dir;
 		}
-		ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
-		ext2_put_page(new_page);
+		ext2_set_link(new_dir, new_de, new_page, page_addr, old_inode, 1);
+		ext2_put_page(new_page, page_addr);
 		new_inode->i_ctime = current_time(new_inode);
 		if (dir_de)
 			drop_nlink(new_inode);
@@ -392,24 +398,25 @@ static int ext2_rename (struct user_namespace * mnt_userns,
 	old_inode->i_ctime = current_time(old_inode);
 	mark_inode_dirty(old_inode);
 
-	ext2_delete_entry (old_de, old_page);
-	ext2_put_page(old_page);
+	ext2_delete_entry(old_de, old_page);
 
 	if (dir_de) {
 		if (old_dir != new_dir)
-			ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);
+			ext2_set_link(old_inode, dir_de, dir_page,
+				      dir_page_addr, new_dir, 0);
 
-		ext2_put_page(dir_page);
+		ext2_put_page(dir_page, dir_page_addr);
 		inode_dec_link_count(old_dir);
 	}
-	return 0;
 
+	ext2_put_page(old_page, old_page_addr);
+	return 0;
 
 out_dir:
 	if (dir_de)
-		ext2_put_page(dir_page);
+		ext2_put_page(dir_page, dir_page_addr);
 out_old:
-	ext2_put_page(old_page);
+	ext2_put_page(old_page, old_page_addr);
 out:
 	return err;
 }