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unicode: Recreate utf8_parse_version()

All filesystems that currently support UTF-8 casefold can fetch the
UTF-8 version from the filesystem metadata stored on disk. They can get
the data stored and directly match it to a integer, so they can skip the
string parsing step, which motivated the removal of this function in the
first place.

However, for tmpfs, the only way to tell the kernel which UTF-8 version
we are about to use is via mount options, using a string. Re-introduce
utf8_parse_version() to be used by tmpfs.

This version differs from the original by skipping the intermediate step
of copying the version string to an auxiliary string before calling
match_token(). This versions calls match_token() in the argument string.
The paramenters are simpler now as well.

utf8_parse_version() was created by 9d53690f0d4 ("unicode: implement
higher level API for string handling") and later removed by 49bd03cc7e9
("unicode: pass a UNICODE_AGE() tripple to utf8_load").

Signed-off-by: André Almeida <andrealmeid@igalia.com>
Link: https://lore.kernel.org/r/20241021-tonyk-tmpfs-v8-4-f443d5814194@igalia.com
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

authored by

André Almeida and committed by
Christian Brauner 142fa60f 04dad6c6

+28
+26
fs/unicode/utf8-core.c
··· 214 214 } 215 215 EXPORT_SYMBOL(utf8_unload); 216 216 217 + /** 218 + * utf8_parse_version - Parse a UTF-8 version number from a string 219 + * 220 + * @version: input string 221 + * 222 + * Returns the parsed version on success, negative code on error 223 + */ 224 + int utf8_parse_version(char *version) 225 + { 226 + substring_t args[3]; 227 + unsigned int maj, min, rev; 228 + static const struct match_token token[] = { 229 + {1, "%d.%d.%d"}, 230 + {0, NULL} 231 + }; 232 + 233 + if (match_token(version, token, args) != 1) 234 + return -EINVAL; 235 + 236 + if (match_int(&args[0], &maj) || match_int(&args[1], &min) || 237 + match_int(&args[2], &rev)) 238 + return -EINVAL; 239 + 240 + return UNICODE_AGE(maj, min, rev); 241 + } 242 + EXPORT_SYMBOL(utf8_parse_version);
+2
include/linux/unicode.h
··· 78 78 struct unicode_map *utf8_load(unsigned int version); 79 79 void utf8_unload(struct unicode_map *um); 80 80 81 + int utf8_parse_version(char *version); 82 + 81 83 #endif /* _LINUX_UNICODE_H */