f2fs: include charset encoding information in the superblock

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

1 files changed, 23 insertions, 0 deletions

diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 3aeacd0aacfd..f9fcca695db9 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -10,6 +10,7 @@
 #include <linux/proc_fs.h>
 #include <linux/f2fs_fs.h>
 #include <linux/seq_file.h>
+#include <linux/unicode.h>
 
 #include "f2fs.h"
 #include "segment.h"
@@ -81,6 +82,19 @@ static ssize_t unusable_show(struct f2fs_attr *a,
                 (unsigned long long)unusable);
 }
 
+static ssize_t encoding_show(struct f2fs_attr *a,
+                struct f2fs_sb_info *sbi, char *buf)
+{
+#ifdef CONFIG_UNICODE
+        if (f2fs_sb_has_casefold(sbi))
+                return snprintf(buf, PAGE_SIZE, "%s (%d.%d.%d)\n",
+                        sbi->s_encoding->charset,
+                        (sbi->s_encoding->version >> 16) & 0xff,
+                        (sbi->s_encoding->version >> 8) & 0xff,
+                        sbi->s_encoding->version & 0xff);
+#endif
+        return snprintf(buf, PAGE_SIZE, "(none)");
+}
 
 static ssize_t lifetime_write_kbytes_show(struct f2fs_attr *a,
                 struct f2fs_sb_info *sbi, char *buf)
@@ -134,6 +148,9 @@ static ssize_t features_show(struct f2fs_attr *a,
         if (f2fs_sb_has_sb_chksum(sbi))
                 len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
                                 len ? ", " : "", "sb_checksum");
+        if (f2fs_sb_has_casefold(sbi))
+                len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
+                                len ? ", " : "", "casefold");
         len += snprintf(buf + len, PAGE_SIZE - len, "\n");
         return len;
 }
@@ -365,6 +382,7 @@ enum feat_id {
         FEAT_INODE_CRTIME,
         FEAT_LOST_FOUND,
         FEAT_SB_CHECKSUM,
+        FEAT_CASEFOLD,
 };
 
 static ssize_t f2fs_feature_show(struct f2fs_attr *a,
@@ -382,6 +400,7 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
         case FEAT_INODE_CRTIME:
         case FEAT_LOST_FOUND:
         case FEAT_SB_CHECKSUM:
+        case FEAT_CASEFOLD:
                 return snprintf(buf, PAGE_SIZE, "supported\n");
         }
         return 0;
@@ -455,6 +474,7 @@ F2FS_GENERAL_RO_ATTR(lifetime_write_kbytes);
 F2FS_GENERAL_RO_ATTR(features);
 F2FS_GENERAL_RO_ATTR(current_reserved_blocks);
 F2FS_GENERAL_RO_ATTR(unusable);
+F2FS_GENERAL_RO_ATTR(encoding);
 
 #ifdef CONFIG_FS_ENCRYPTION
 F2FS_FEATURE_RO_ATTR(encryption, FEAT_CRYPTO);
@@ -471,6 +491,7 @@ F2FS_FEATURE_RO_ATTR(quota_ino, FEAT_QUOTA_INO);
 F2FS_FEATURE_RO_ATTR(inode_crtime, FEAT_INODE_CRTIME);
 F2FS_FEATURE_RO_ATTR(lost_found, FEAT_LOST_FOUND);
 F2FS_FEATURE_RO_ATTR(sb_checksum, FEAT_SB_CHECKSUM);
+F2FS_FEATURE_RO_ATTR(casefold, FEAT_CASEFOLD);
 
 #define ATTR_LIST(name) (&f2fs_attr_##name.attr)
 static struct attribute *f2fs_attrs[] = {
@@ -515,6 +536,7 @@ static struct attribute *f2fs_attrs[] = {
         ATTR_LIST(features),
         ATTR_LIST(reserved_blocks),
         ATTR_LIST(current_reserved_blocks),
+        ATTR_LIST(encoding),
         NULL,
 };
 ATTRIBUTE_GROUPS(f2fs);
@@ -535,6 +557,7 @@ static struct attribute *f2fs_feat_attrs[] = {
         ATTR_LIST(inode_crtime),
         ATTR_LIST(lost_found),
         ATTR_LIST(sb_checksum),
+        ATTR_LIST(casefold),
         NULL,
 };
 ATTRIBUTE_GROUPS(f2fs_feat);