f2fs: introduce F2FS_FEATURE_LOST_FOUND feature

This patch introduces a new feature, F2FS_FEATURE_LOST_FOUND, which
is set by mkfs. mkfs creates a directory named lost+found, which saves
unreachable files. If fsck finds a file which has no parent, or its
parent is removed by fsck, the file will be placed under lost+found
directory by fsck.

lost+found directory could not be encrypted. As a result, the root
directory cannot be encrypted too. So if LOST_FOUND feature is enabled,
let's avoid to encrypt root directory.

Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 419eaacf3366..dcdae3f932e2 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1891,6 +1891,18 @@ static int f2fs_get_context(struct inode *inode, void *ctx, size_t len)
 static int f2fs_set_context(struct inode *inode, const void *ctx, size_t len,
 							void *fs_data)
 {
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+
+	/*
+	 * Encrypting the root directory is not allowed because fsck
+	 * expects lost+found directory to exist and remain unencrypted
+	 * if LOST_FOUND feature is enabled.
+	 *
+	 */
+	if (f2fs_sb_has_lost_found(sbi->sb) &&
+			inode->i_ino == F2FS_ROOT_INO(sbi))
+		return -EPERM;
+
 	return f2fs_setxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
 				F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 				ctx, len, fs_data, XATTR_CREATE);