[RFC PATCH 2/2] f2fs: introduce lost+found feature

[Sheng Yong <shengyong1@huawei.com>]

Introduce lost+found feature. The lost+found is a directory which saves
unreachable files. If f2fsck finds a file which has no parent, or the
parent is removed by f2fsck, the file will be placed in lost+found
directory.

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

Signed-off-by: Sheng Yong <shengyong1@huawei.com>
---
 fs/f2fs/f2fs.h  |  2 ++
 fs/f2fs/super.c | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index a60d56a96f9b..d9c9be6ea5d5 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -125,6 +125,7 @@ struct f2fs_mount_info {
 #define F2FS_FEATURE_FLEXIBLE_INLINE_XATTR	0x0040
 #define F2FS_FEATURE_QUOTA_INO		0x0080
 #define F2FS_FEATURE_INODE_CRTIME	0x0100
+#define F2FS_FEATURE_LOST_FOUND		0x0200
 
 #define F2FS_HAS_FEATURE(sb, mask)					\
 	((F2FS_SB(sb)->raw_super->feature & cpu_to_le32(mask)) != 0)
@@ -3186,6 +3187,7 @@ F2FS_FEATURE_FUNCS(inode_chksum, INODE_CHKSUM);
 F2FS_FEATURE_FUNCS(flexible_inline_xattr, FLEXIBLE_INLINE_XATTR);
 F2FS_FEATURE_FUNCS(quota_ino, QUOTA_INO);
 F2FS_FEATURE_FUNCS(inode_crtime, INODE_CRTIME);
+F2FS_FEATURE_FUNCS(lost_found, LOST_FOUND);
 
 #ifdef CONFIG_BLK_DEV_ZONED
 static inline int get_blkz_type(struct f2fs_sb_info *sbi,
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index b39ab55ab1b5..5f536e878d21 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1797,6 +1797,18 @@ 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 f2fsck
+	 * 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);
-- 
2.11.0


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