fs/adfs: dir: improve update failure handling

When we update a directory, a number of errors may happen. If we failed
to find the entry to update, we can just release the directory buffers
as normal.

However, if we have some other error, we may have partially updated the
buffers, resulting in an invalid directory. In this case, we need to
discard the buffers to avoid writing the contents back to the media, and
later re-read the directory from the media.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/adfs/dir.c

@@ -64,12 +64,8 @@ int adfs_dir_copyto(struct adfs_dir *dir, unsigned int offset, const void *src,
 	return 0;
 }
 
-void adfs_dir_relse(struct adfs_dir *dir)
+static void __adfs_dir_cleanup(struct adfs_dir *dir)
 {
-	unsigned int i;
-
-	for (i = 0; i < dir->nr_buffers; i++)
-		brelse(dir->bhs[i]);
 	dir->nr_buffers = 0;
 
 	if (dir->bhs != dir->bh)
@@ -78,6 +74,26 @@ void adfs_dir_relse(struct adfs_dir *dir)
 	dir->sb = NULL;
 }
 
+void adfs_dir_relse(struct adfs_dir *dir)
+{
+	unsigned int i;
+
+	for (i = 0; i < dir->nr_buffers; i++)
+		brelse(dir->bhs[i]);
+
+	__adfs_dir_cleanup(dir);
+}
+
+static void adfs_dir_forget(struct adfs_dir *dir)
+{
+	unsigned int i;
+
+	for (i = 0; i < dir->nr_buffers; i++)
+		bforget(dir->bhs[i]);
+
+	__adfs_dir_cleanup(dir);
+}
+
 int adfs_dir_read_buffers(struct super_block *sb, u32 indaddr,
 			  unsigned int size, struct adfs_dir *dir)
 {
@@ -288,20 +304,28 @@ adfs_dir_update(struct super_block *sb, struct object_info *obj, int wait)
 		goto unlock;
 
 	ret = ops->update(&dir, obj);
+	if (ret)
+		goto forget;
 	up_write(&adfs_dir_rwsem);
 
-	if (ret == 0)
-		adfs_dir_mark_dirty(&dir);
+	adfs_dir_mark_dirty(&dir);
 
-	if (wait) {
-		int err = adfs_dir_sync(&dir);
-		if (!ret)
-			ret = err;
-	}
+	if (wait)
+		ret = adfs_dir_sync(&dir);
 
 	adfs_dir_relse(&dir);
 	return ret;
 
+	/*
+	 * If the updated failed because the entry wasn't found, we can
+	 * just release the buffers. If it was any other error, forget
+	 * the dirtied buffers so they aren't written back to the media.
+	 */
+forget:
+	if (ret == -ENOENT)
+		adfs_dir_relse(&dir);
+	else
+		adfs_dir_forget(&dir);
 unlock:
 	up_write(&adfs_dir_rwsem);
 #endif