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Date:   Tue, 16 Jul 2019 20:14:07 -0700
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Subject: [PATCH v2 1/2] f2fs: include charset encoding information in the superblock
From:   Daniel Rosenberg <drosen@google.com>
To:     Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>,
        Jonathan Corbet <corbet@lwn.net>,
        linux-f2fs-devel@lists.sourceforge.net
Cc:     linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, kernel-team@android.com,
        Daniel Rosenberg <drosen@google.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Add charset encoding to f2fs to support casefolding. It is modeled after
the same feature introduced in commit c83ad55eaa91 ("ext4: include charset
encoding information in the superblock")

Currently this is not compatible with encryption, similar to the current
ext4 imlpementation. This will change in the future.

From the ext4 patch:
"""
The s_encoding field stores a magic number indicating the encoding
format and version used globally by file and directory names in the
filesystem.  The s_encoding_flags defines policies for using the charset
encoding, like how to handle invalid sequences.  The magic number is
mapped to the exact charset table, but the mapping is specific to ext4.
Since we don't have any commitment to support old encodings, the only
encoding I am supporting right now is utf8-12.1.0.

The current implementation prevents the user from enabling encoding and
per-directory encryption on the same filesystem at the same time.  The
incompatibility between these features lies in how we do efficient
directory searches when we cannot be sure the encryption of the user
provided fname will match the actual hash stored in the disk without
decrypting every directory entry, because of normalization cases.  My
quickest solution is to simply block the concurrent use of these
features for now, and enable it later, once we have a better solution.
"""

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs/f2fs/f2fs.h          |  6 +++
 fs/f2fs/super.c         | 81 +++++++++++++++++++++++++++++++++++++++++
 include/linux/f2fs_fs.h |  9 ++++-
 3 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 17382da7f0bd9..c6c7904572d0d 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -153,6 +153,7 @@ struct f2fs_mount_info {
 #define F2FS_FEATURE_LOST_FOUND		0x0200
 #define F2FS_FEATURE_VERITY		0x0400	/* reserved */
 #define F2FS_FEATURE_SB_CHKSUM		0x0800
+#define F2FS_FEATURE_CASEFOLD		0x1000
 
 #define __F2FS_HAS_FEATURE(raw_super, mask)				\
 	((raw_super->feature & cpu_to_le32(mask)) != 0)
@@ -1169,6 +1170,10 @@ struct f2fs_sb_info {
 	int valid_super_block;			/* valid super block no */
 	unsigned long s_flag;				/* flags for sbi */
 	struct mutex writepages;		/* mutex for writepages() */
+#ifdef CONFIG_UNICODE
+	struct unicode_map *s_encoding;
+	__u16 s_encoding_flags;
+#endif
 
 #ifdef CONFIG_BLK_DEV_ZONED
 	unsigned int blocks_per_blkz;		/* F2FS blocks per zone */
@@ -3562,6 +3567,7 @@ F2FS_FEATURE_FUNCS(quota_ino, QUOTA_INO);
 F2FS_FEATURE_FUNCS(inode_crtime, INODE_CRTIME);
 F2FS_FEATURE_FUNCS(lost_found, LOST_FOUND);
 F2FS_FEATURE_FUNCS(sb_chksum, SB_CHKSUM);
+F2FS_FEATURE_FUNCS(casefold, CASEFOLD);
 
 #ifdef CONFIG_BLK_DEV_ZONED
 static inline bool f2fs_blkz_is_seq(struct f2fs_sb_info *sbi, int devi,
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 6de6cda440315..7927071ef5e95 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -23,6 +23,7 @@
 #include <linux/f2fs_fs.h>
 #include <linux/sysfs.h>
 #include <linux/quota.h>
+#include <linux/unicode.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -222,6 +223,36 @@ void f2fs_printk(struct f2fs_sb_info *sbi, const char *fmt, ...)
 	va_end(args);
 }
 
+#ifdef CONFIG_UNICODE
+static const struct f2fs_sb_encodings {
+	__u16 magic;
+	char *name;
+	char *version;
+} f2fs_sb_encoding_map[] = {
+	{F2FS_ENC_UTF8_12_1, "utf8", "12.1.0"},
+};
+
+static int f2fs_sb_read_encoding(const struct f2fs_super_block *sb,
+				 const struct f2fs_sb_encodings **encoding,
+				 __u16 *flags)
+{
+	__u16 magic = le16_to_cpu(sb->s_encoding);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(f2fs_sb_encoding_map); i++)
+		if (magic == f2fs_sb_encoding_map[i].magic)
+			break;
+
+	if (i >= ARRAY_SIZE(f2fs_sb_encoding_map))
+		return -EINVAL;
+
+	*encoding = &f2fs_sb_encoding_map[i];
+	*flags = le16_to_cpu(sb->s_encoding_flags);
+
+	return 0;
+}
+#endif
+
 static inline void limit_reserve_root(struct f2fs_sb_info *sbi)
 {
 	block_t limit = min((sbi->user_block_count << 1) / 1000,
@@ -798,6 +829,13 @@ static int parse_options(struct super_block *sb, char *options)
 		return -EINVAL;
 	}
 #endif
+#ifndef CONFIG_UNICODE
+	if (f2fs_sb_has_casefold(sbi)) {
+		f2fs_err(sbi,
+			"Filesystem with casefold feature cannot be mounted without CONFIG_UNICODE");
+		return -EINVAL;
+	}
+#endif
 
 	if (F2FS_IO_SIZE_BITS(sbi) && !test_opt(sbi, LFS)) {
 		f2fs_err(sbi, "Should set mode=lfs with %uKB-sized IO",
@@ -1089,6 +1127,9 @@ static void f2fs_put_super(struct super_block *sb)
 	destroy_percpu_info(sbi);
 	for (i = 0; i < NR_PAGE_TYPE; i++)
 		kvfree(sbi->write_io[i]);
+#ifdef CONFIG_UNICODE
+	utf8_unload(sbi->s_encoding);
+#endif
 	kvfree(sbi);
 }
 
@@ -3126,6 +3167,42 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_maxbytes = sbi->max_file_blocks <<
 				le32_to_cpu(raw_super->log_blocksize);
 	sb->s_max_links = F2FS_LINK_MAX;
+#ifdef CONFIG_UNICODE
+	if (f2fs_sb_has_casefold(sbi) && !sbi->s_encoding) {
+		const struct f2fs_sb_encodings *encoding_info;
+		struct unicode_map *encoding;
+		__u16 encoding_flags;
+
+		if (f2fs_sb_has_encrypt(sbi)) {
+			f2fs_err(sbi,
+				"Can't mount with encoding and encryption");
+			goto free_options;
+		}
+
+		if (f2fs_sb_read_encoding(raw_super, &encoding_info,
+					  &encoding_flags)) {
+			f2fs_err(sbi,
+				 "Encoding requested by superblock is unknown");
+			goto free_options;
+		}
+
+		encoding = utf8_load(encoding_info->version);
+		if (IS_ERR(encoding)) {
+			f2fs_err(sbi,
+				 "can't mount with superblock charset: %s-%s "
+				 "not supported by the kernel. flags: 0x%x.",
+				 encoding_info->name, encoding_info->version,
+				 encoding_flags);
+			goto free_options;
+		}
+		f2fs_info(sbi, "Using encoding defined by superblock: "
+			 "%s-%s with flags 0x%hx", encoding_info->name,
+			 encoding_info->version?:"\b", encoding_flags);
+
+		sbi->s_encoding = encoding;
+		sbi->s_encoding_flags = encoding_flags;
+	}
+#endif
 
 #ifdef CONFIG_QUOTA
 	sb->dq_op = &f2fs_quota_operations;
@@ -3477,6 +3554,10 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 free_bio_info:
 	for (i = 0; i < NR_PAGE_TYPE; i++)
 		kvfree(sbi->write_io[i]);
+
+#ifdef CONFIG_UNICODE
+	utf8_unload(sbi->s_encoding);
+#endif
 free_options:
 #ifdef CONFIG_QUOTA
 	for (i = 0; i < MAXQUOTAS; i++)
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index 65559900d4d76..b7c9c7f721339 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -36,6 +36,11 @@
 
 #define F2FS_MAX_QUOTAS		3
 
+#define F2FS_ENC_UTF8_12_1	1
+#define F2FS_ENC_STRICT_MODE_FL	(1 << 0)
+#define f2fs_has_strict_mode(sbi) \
+	(sbi->s_encoding_flags & F2FS_ENC_STRICT_MODE_FL)
+
 #define F2FS_IO_SIZE(sbi)	(1 << F2FS_OPTION(sbi).write_io_size_bits) /* Blocks */
 #define F2FS_IO_SIZE_KB(sbi)	(1 << (F2FS_OPTION(sbi).write_io_size_bits + 2)) /* KB */
 #define F2FS_IO_SIZE_BYTES(sbi)	(1 << (F2FS_OPTION(sbi).write_io_size_bits + 12)) /* B */
@@ -109,7 +114,9 @@ struct f2fs_super_block {
 	struct f2fs_device devs[MAX_DEVICES];	/* device list */
 	__le32 qf_ino[F2FS_MAX_QUOTAS];	/* quota inode numbers */
 	__u8 hot_ext_count;		/* # of hot file extension */
-	__u8 reserved[310];		/* valid reserved region */
+	__le16  s_encoding;		/* Filename charset encoding */
+	__le16  s_encoding_flags;	/* Filename charset encoding flags */
+	__u8 reserved[306];		/* valid reserved region */
 	__le32 crc;			/* checksum of superblock */
 } __packed;
 
-- 
2.22.0.510.g264f2c817a-goog