fs/ext2: Use ext2_put_page

There are 3 places in namei.c where the equivalent of ext2_put_page() is
open coded on a page which was returned from the ext2_get_page() call
[through the use of ext2_find_entry() and ext2_dotdot()].

Move ext2_put_page() to ext2.h and use it in namei.c

Also add a comment regarding the proper way to release the page returned
from ext2_find_entry() and ext2_dotdot().

Link: https://lore.kernel.org/r/20201112174244.701325-1-ira.weiny@intel.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/dir.c

@@ -66,12 +66,6 @@ static inline unsigned ext2_chunk_size(struct inode *inode)
 	return inode->i_sb->s_blocksize;
 }
 
-static inline void ext2_put_page(struct page *page)
-{
-	kunmap(page);
-	put_page(page);
-}
-
 /*
  * Return the offset into page `page_nr' of the last valid
  * byte in that page, plus one.
@@ -336,6 +330,8 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
  * returns the page in which the entry was found (as a parameter - res_page),
  * and the entry itself. Page is returned mapped and unlocked.
  * Entry is guaranteed to be valid.
+ *
+ * On Success ext2_put_page() should be called on *res_page.
  */
 struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
 			const struct qstr *child, struct page **res_page)
@@ -401,6 +397,12 @@ found:
 	return de;
 }
 
+/**
+ * Return the '..' directory entry and the page in which the entry was found
+ * (as a parameter - p).
+ *
+ * On Success ext2_put_page() should be called on *p.
+ */
 struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
 {
 	struct page *page = ext2_get_page(dir, 0, 0);

fs/ext2/ext2.h

@@ -16,6 +16,8 @@
 #include <linux/blockgroup_lock.h>
 #include <linux/percpu_counter.h>
 #include <linux/rbtree.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
 
 /* XXX Here for now... not interested in restructing headers JUST now */
 
@@ -745,6 +747,11 @@ extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
 extern int ext2_empty_dir (struct inode *);
 extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
 extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int);
+static inline void ext2_put_page(struct page *page)
+{
+	kunmap(page);
+	put_page(page);
+}
 
 /* ialloc.c */
 extern struct inode * ext2_new_inode (struct inode *, umode_t, const struct qstr *);

fs/ext2/namei.c

@@ -389,23 +389,18 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
 	if (dir_de) {
 		if (old_dir != new_dir)
 			ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);
-		else {
-			kunmap(dir_page);
-			put_page(dir_page);
-		}
+		else
+			ext2_put_page(dir_page);
 		inode_dec_link_count(old_dir);
 	}
 	return 0;
 
 
 out_dir:
-	if (dir_de) {
-		kunmap(dir_page);
-		put_page(dir_page);
-	}
+	if (dir_de)
+		ext2_put_page(dir_page);
 out_old:
-	kunmap(old_page);
-	put_page(old_page);
+	ext2_put_page(old_page);
 out:
 	return err;
 }