Support for encoding is considered an incompatible feature, since it has
potential to create collisions of file names in existing filesystems.
If the feature flag is not enabled, the entire filesystem will operate
on opaque byte sequences, respecting the original behavior.
The charset data is encoded in a new field in the superblock using a
magic number specific to ext4. This is the easiest way I found to avoid
writing the name of the charset in the superblock. The magic number is
mapped to the exact NLS table, but the mapping is specific to ext4.
Since we don't have any commitment to support old encodings, the only
encodings I am supporting right now is utf8n-10.0.0 and ascii, both
using the NLS abstraction.
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.
Changes since v1:
- Guard code with CONFIG_NLS.
- Use 16 bits for s_ioencoding.
- Split mount option from this patch
Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxxxx>
---
fs/ext4/ext4.h | 19 ++++++++++++-
fs/ext4/super.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 91 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ac05bd86643a..6bdaba9c6923 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1190,6 +1190,11 @@ extern void ext4_set_bits(void *bm, int cur, int len);
/* Metadata checksum algorithm codes */
#define EXT4_CRC32C_CHKSUM 1
+/* Be careful when modifying these flags. The lower byte must match the
+ * NLS flags. */
+
+#define EXT4_ENC_NLS_FL_MASK 0x00FF
+
/*
* Structure of the super block
*/
@@ -1316,7 +1321,9 @@ struct ext4_super_block {
__u8 s_first_error_time_hi;
__u8 s_last_error_time_hi;
__u8 s_pad[2];
- __le32 s_reserved[96]; /* Padding to the end of the block */
+ __le16 s_ioencoding; /* charset encoding */
+ __le16 s_ioencoding_flags; /* charset encoding flags */
+ __le32 s_reserved[95]; /* Padding to the end of the block */
__le32 s_checksum; /* crc32c(superblock) */
};
@@ -1341,6 +1348,8 @@ struct ext4_super_block {
/* Number of quota types we support */
#define EXT4_MAXQUOTAS 3
+struct ext4_sb_encodings;
+
/*
* fourth extended-fs super-block data in memory
*/
@@ -1390,6 +1399,11 @@ struct ext4_sb_info {
struct kobject s_kobj;
struct completion s_kobj_unregister;
struct super_block *s_sb;
+#ifdef CONFIG_NLS
+ const struct ext4_sb_encodings *encoding_info;
+ struct nls_table *encoding;
+ __u16 encoding_flags;
+#endif
/* Journaling */
struct journal_s *s_journal;
@@ -1665,6 +1679,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
#define EXT4_FEATURE_INCOMPAT_LARGEDIR 0x4000 /* >2GB or 3-lvl htree */
#define EXT4_FEATURE_INCOMPAT_INLINE_DATA 0x8000 /* data in inode */
#define EXT4_FEATURE_INCOMPAT_ENCRYPT 0x10000
+#define EXT4_FEATURE_INCOMPAT_IOENCODING 0x20000
#define EXT4_FEATURE_COMPAT_FUNCS(name, flagname) \
static inline bool ext4_has_feature_##name(struct super_block *sb) \
@@ -1753,6 +1768,7 @@ EXT4_FEATURE_INCOMPAT_FUNCS(csum_seed, CSUM_SEED)
EXT4_FEATURE_INCOMPAT_FUNCS(largedir, LARGEDIR)
EXT4_FEATURE_INCOMPAT_FUNCS(inline_data, INLINE_DATA)
EXT4_FEATURE_INCOMPAT_FUNCS(encrypt, ENCRYPT)
+EXT4_FEATURE_INCOMPAT_FUNCS(ioencoding, IOENCODING)
#define EXT2_FEATURE_COMPAT_SUPP EXT4_FEATURE_COMPAT_EXT_ATTR
#define EXT2_FEATURE_INCOMPAT_SUPP (EXT4_FEATURE_INCOMPAT_FILETYPE| \
@@ -1780,6 +1796,7 @@ EXT4_FEATURE_INCOMPAT_FUNCS(encrypt, ENCRYPT)
EXT4_FEATURE_INCOMPAT_MMP | \
EXT4_FEATURE_INCOMPAT_INLINE_DATA | \
EXT4_FEATURE_INCOMPAT_ENCRYPT | \
+ EXT4_FEATURE_INCOMPAT_IOENCODING | \
EXT4_FEATURE_INCOMPAT_CSUM_SEED | \
EXT4_FEATURE_INCOMPAT_LARGEDIR)
#define EXT4_FEATURE_RO_COMPAT_SUPP (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index a430fb3e9720..ccf4742fea3b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -42,6 +42,7 @@
#include <linux/cleancache.h>
#include <linux/uaccess.h>
#include <linux/iversion.h>
+#include <linux/nls.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
@@ -1010,6 +1011,10 @@ static void ext4_put_super(struct super_block *sb)
crypto_free_shash(sbi->s_chksum_driver);
kfree(sbi->s_blockgroup_lock);
fs_put_dax(sbi->s_daxdev);
+#ifdef CONFIG_NLS
+ unload_nls(sbi->encoding);
+ kfree(sbi->encoding_info);
+#endif
kfree(sbi);
}
@@ -1703,6 +1708,31 @@ static const struct mount_opts {
{Opt_err, 0, 0}
};
+#ifdef CONFIG_NLS
+static const struct ext4_sb_encodings {
+ char *name;
+ char *version;
+} ext4_sb_encoding_map[] = {
+ /* 0x0 */ {"ascii", NULL},
+ /* 0x1 */ {"utf8", "10.0.0"},
+};
+
+static int
+ext4_sb_read_encoding(const struct ext4_super_block *es,
+ const struct ext4_sb_encodings **encoding, __u16 *flags)
+{
+ __u16 magic = le16_to_cpu(es->s_ioencoding);
+
+ if (magic >= ARRAY_SIZE(ext4_sb_encoding_map))
+ return -EINVAL;
+
+ *encoding = &ext4_sb_encoding_map[magic];
+ *flags = le16_to_cpu(es->s_ioencoding_flags);
+
+ return 0;
+}
+#endif
+
static int handle_mount_opt(struct super_block *sb, char *opt, int token,
substring_t *args, unsigned long *journal_devnum,
unsigned int *journal_ioprio, int is_remount)
@@ -3515,6 +3545,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
int err = 0;
unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
ext4_group_t first_not_zeroed;
+#ifdef CONFIG_NLS
+ struct nls_table *encoding;
+ const struct ext4_sb_encodings *encoding_info;
+ __u16 nls_flags;
+#endif
if ((data && !orig_data) || !sbi)
goto out_free_base;
@@ -3687,6 +3722,39 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
&journal_ioprio, 0))
goto failed_mount;
+#ifdef CONFIG_NLS
+ if (ext4_has_feature_ioencoding(sb) && !sbi->encoding) {
+ if (ext4_has_feature_encrypt(sb)) {
+ ext4_msg(sb, KERN_ERR,
+ "Can't mount with both encoding and encryption");
+ goto failed_mount;
+ }
+
+ if (ext4_sb_read_encoding(es, &encoding_info, &nls_flags)) {
+ ext4_msg(sb, KERN_ERR,
+ "Encoding requested by superblock is unknown");
+ goto failed_mount;
+ }
+
+ encoding = load_nls_version(encoding_info->name,
+ encoding_info->version,
+ nls_flags & EXT4_ENC_NLS_FL_MASK);
+ if (IS_ERR(encoding)) {
+ ext4_msg(sb, KERN_ERR, "can't mount with superblock charset: "
+ "%s-%s not supported by the kernel. flags: 0x%x",
+ encoding_info->name, encoding_info->version,
+ nls_flags);
+ goto failed_mount;
+ }
+ ext4_msg(sb, KERN_INFO,"Using encoding defined by superblock: "
+ "%s-%s with flags 0x%hx", encoding_info->name,
+ encoding_info->version?:"\b", nls_flags);
+
+ sbi->encoding = encoding;
+ sbi->encoding_flags = nls_flags;
+ }
+#endif
+
if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
printk_once(KERN_WARNING "EXT4-fs: Warning: mounting "
"with data=journal disables delayed "
@@ -4527,6 +4595,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
failed_mount:
if (sbi->s_chksum_driver)
crypto_free_shash(sbi->s_chksum_driver);
+
+#ifdef CONFIG_NLS
+ unload_nls(sbi->encoding);
+#endif
+
#ifdef CONFIG_QUOTA
for (i = 0; i < EXT4_MAXQUOTAS; i++)
kfree(sbi->s_qf_names[i]);
--
2.19.0
