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From:   Gabriel Krisman Bertazi <krisman@collabora.com>
To:     Shreeya Patel <shreeya.patel@collabora.com>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        kernel@collabora.com, gustavo.padovan@collabora.com,
        andre.almeida@collabora.com
Subject: Re: [PATCH 3/3] fs: unicode: Add utf8 module and a unicode layer
Organization: Collabora
References: <20210313231214.383576-1-shreeya.patel@collabora.com>
        <20210313231214.383576-4-shreeya.patel@collabora.com>
Date:   Sat, 13 Mar 2021 20:49:38 -0500
In-Reply-To: <20210313231214.383576-4-shreeya.patel@collabora.com> (Shreeya
        Patel's message of "Sun, 14 Mar 2021 04:42:13 +0530")
Message-ID: <8735wymrm5.fsf@collabora.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Shreeya Patel <shreeya.patel@collabora.com> writes:

> utf8data.h_shipped has a large database table which is an auto-generated
> decodification trie for the unicode normalization functions.
> It is not necessary to carry this large table in the kernel hence make
> UTF-8 encoding loadable by converting it into a module.
> Also, modify the file called unicode-core which will act as a layer for
> unicode subsystem. It will load the UTF-8 module and access it's functions
> whenever any filesystem that needs unicode is mounted.
>
> Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>

Hi Shreeya,

> ---
>  fs/unicode/Kconfig        |   7 +-
>  fs/unicode/Makefile       |   5 +-
>  fs/unicode/unicode-core.c | 201 ++++++-------------------------
>  fs/unicode/utf8-core.c    | 112 +++++++++++++++++
>  fs/unicode/utf8mod.c      | 246 ++++++++++++++++++++++++++++++++++++++
>  include/linux/unicode.h   |  20 ++++
>  6 files changed, 427 insertions(+), 164 deletions(-)
>  create mode 100644 fs/unicode/utf8-core.c
>  create mode 100644 fs/unicode/utf8mod.c
>
> diff --git a/fs/unicode/Kconfig b/fs/unicode/Kconfig
> index 2c27b9a5cd6c..33a27deef729 100644
> --- a/fs/unicode/Kconfig
> +++ b/fs/unicode/Kconfig
> @@ -8,7 +8,12 @@ config UNICODE
>  	  Say Y here to enable UTF-8 NFD normalization and NFD+CF casefolding
>  	  support.
>  
> +config UNICODE_UTF8
> +	tristate "UTF-8 module"
> +	depends on UNICODE
> +	default m
> +
>  config UNICODE_NORMALIZATION_SELFTEST
>  	tristate "Test UTF-8 normalization support"
> -	depends on UNICODE
> +	depends on UNICODE_UTF8
>  	default n
> diff --git a/fs/unicode/Makefile b/fs/unicode/Makefile
> index fbf9a629ed0d..9dbb04194b32 100644
> --- a/fs/unicode/Makefile
> +++ b/fs/unicode/Makefile
> @@ -1,11 +1,14 @@
>  # SPDX-License-Identifier: GPL-2.0
>  
>  obj-$(CONFIG_UNICODE) += unicode.o
> +obj-$(CONFIG_UNICODE_UTF8) += utf8.o
>  obj-$(CONFIG_UNICODE_NORMALIZATION_SELFTEST) += utf8-selftest.o
>  
> -unicode-y := utf8-norm.o unicode-core.o
> +unicode-y := unicode-core.o
> +utf8-y := utf8mod.o utf8-norm.o
>  
>  $(obj)/utf8-norm.o: $(obj)/utf8data.h
> +$(obj)/utf8mod.o: $(obj)/utf8-norm.o
>  
>  # In the normal build, the checked-in utf8data.h is just shipped.
>  #
> diff --git a/fs/unicode/unicode-core.c b/fs/unicode/unicode-core.c
> index d5f09e022ac5..b832341f1e7b 100644
> --- a/fs/unicode/unicode-core.c
> +++ b/fs/unicode/unicode-core.c
> @@ -7,70 +7,29 @@
>  #include <linux/errno.h>
>  #include <linux/unicode.h>
>  #include <linux/stringhash.h>
> +#include <linux/delay.h>
>  
> -#include "utf8n.h"
> +struct unicode_ops *utf8_ops;
> +
> +static int unicode_load_module(void);

This is unnecessary
>  
>  int unicode_validate(const struct unicode_map *um, const struct qstr *str)
>  {
> -	const struct utf8data *data = utf8nfdi(um->version);
> -
> -	if (utf8nlen(data, str->name, str->len) < 0)
> -		return -1;
> -	return 0;
> +	return utf8_ops->validate(um, str);
>  }
>  EXPORT_SYMBOL(unicode_validate);
>  
>  int unicode_strncmp(const struct unicode_map *um,
>  		    const struct qstr *s1, const struct qstr *s2)
>  {
> -	const struct utf8data *data = utf8nfdi(um->version);
> -	struct utf8cursor cur1, cur2;
> -	int c1, c2;
> -
> -	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
> -		return -EINVAL;
> -
> -	if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
> -		return -EINVAL;
> -
> -	do {
> -		c1 = utf8byte(&cur1);
> -		c2 = utf8byte(&cur2);
> -
> -		if (c1 < 0 || c2 < 0)
> -			return -EINVAL;
> -		if (c1 != c2)
> -			return 1;
> -	} while (c1);
> -
> -	return 0;
> +	return utf8_ops->strncmp(um, s1, s2);
>  }

I think these would go on a header file and  inlined.

>  EXPORT_SYMBOL(unicode_strncmp);
>  
>  int unicode_strncasecmp(const struct unicode_map *um,
>  			const struct qstr *s1, const struct qstr *s2)
>  {
> -	const struct utf8data *data = utf8nfdicf(um->version);
> -	struct utf8cursor cur1, cur2;
> -	int c1, c2;
> -
> -	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
> -		return -EINVAL;
> -
> -	if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
> -		return -EINVAL;
> -
> -	do {
> -		c1 = utf8byte(&cur1);
> -		c2 = utf8byte(&cur2);
> -
> -		if (c1 < 0 || c2 < 0)
> -			return -EINVAL;
> -		if (c1 != c2)
> -			return 1;
> -	} while (c1);
> -
> -	return 0;
> +	return utf8_ops->strncasecmp(um, s1, s2);
>  }
>  EXPORT_SYMBOL(unicode_strncasecmp);
>  
> @@ -81,155 +40,73 @@ int unicode_strncasecmp_folded(const struct unicode_map *um,
>  			       const struct qstr *cf,
>  			       const struct qstr *s1)
>  {
> -	const struct utf8data *data = utf8nfdicf(um->version);
> -	struct utf8cursor cur1;
> -	int c1, c2;
> -	int i = 0;
> -
> -	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
> -		return -EINVAL;
> -
> -	do {
> -		c1 = utf8byte(&cur1);
> -		c2 = cf->name[i++];
> -		if (c1 < 0)
> -			return -EINVAL;
> -		if (c1 != c2)
> -			return 1;
> -	} while (c1);
> -
> -	return 0;
> +	return utf8_ops->strncasecmp_folded(um, cf, s1);
>  }
>  EXPORT_SYMBOL(unicode_strncasecmp_folded);
>  
>  int unicode_casefold(const struct unicode_map *um, const struct qstr *str,
>  		     unsigned char *dest, size_t dlen)
>  {
> -	const struct utf8data *data = utf8nfdicf(um->version);
> -	struct utf8cursor cur;
> -	size_t nlen = 0;
> -
> -	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
> -		return -EINVAL;
> -
> -	for (nlen = 0; nlen < dlen; nlen++) {
> -		int c = utf8byte(&cur);
> -
> -		dest[nlen] = c;
> -		if (!c)
> -			return nlen;
> -		if (c == -1)
> -			break;
> -	}
> -	return -EINVAL;
> +	return utf8_ops->casefold(um, str, dest, dlen);
>  }
>  EXPORT_SYMBOL(unicode_casefold);
>  
>  int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
>  			  struct qstr *str)
>  {
> -	const struct utf8data *data = utf8nfdicf(um->version);
> -	struct utf8cursor cur;
> -	int c;
> -	unsigned long hash = init_name_hash(salt);
> -
> -	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
> -		return -EINVAL;
> -
> -	while ((c = utf8byte(&cur))) {
> -		if (c < 0)
> -			return -EINVAL;
> -		hash = partial_name_hash((unsigned char)c, hash);
> -	}
> -	str->hash = end_name_hash(hash);
> -	return 0;
> +	return utf8_ops->casefold_hash(um, salt, str);
>  }
>  EXPORT_SYMBOL(unicode_casefold_hash);
>  
>  int unicode_normalize(const struct unicode_map *um, const struct qstr *str,
>  		      unsigned char *dest, size_t dlen)
>  {
> -	const struct utf8data *data = utf8nfdi(um->version);
> -	struct utf8cursor cur;
> -	ssize_t nlen = 0;
> +	return utf8_ops->normalize(um, str, dest, dlen);
> +}
> +EXPORT_SYMBOL(unicode_normalize);
>  
> -	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
> -		return -EINVAL;
> +struct unicode_map *unicode_load(const char *version)
> +{
> +	int ret = unicode_load_module();
>  
> -	for (nlen = 0; nlen < dlen; nlen++) {
> -		int c = utf8byte(&cur);
> +	if (ret)
> +		return ERR_PTR(ret);
>  
> -		dest[nlen] = c;
> -		if (!c)
> -			return nlen;
> -		if (c == -1)
> -			break;
> -	}
> -	return -EINVAL;
> +	else
> +		return utf8_ops->load(version);
>  }
> -EXPORT_SYMBOL(unicode_normalize);
> +EXPORT_SYMBOL(unicode_load);
>  
> -static int unicode_parse_version(const char *version, unsigned int *maj,
> -				 unsigned int *min, unsigned int *rev)
> +void unicode_unload(struct unicode_map *um)
>  {
> -	substring_t args[3];
> -	char version_string[12];
> -	static const struct match_token token[] = {
> -		{1, "%d.%d.%d"},
> -		{0, NULL}
> -	};
> +	kfree(um);
> +}
> +EXPORT_SYMBOL(unicode_unload);
>  
> -	strncpy(version_string, version, sizeof(version_string));
> +static int unicode_load_module(void)
> +{
> +	int ret = request_module("utf8");
>  
> -	if (match_token(version_string, token, args) != 1)
> -		return -EINVAL;
> +	msleep(100);

I think I misunderstood when you mentioned you did this msleep.  It was
ok to debug the issue you were observing, but it is not a solution.
Setting an arbitrary amount of time will either waste time, or you can
still fail if things take longer than expected.  There are mechanisms to
load and wait on a module.  See how fs/nls/nls_base.c do exactly this.

> -	if (match_int(&args[0], maj) || match_int(&args[1], min) ||
> -	    match_int(&args[2], rev))
> -		return -EINVAL;
> +	if (ret) {
> +		pr_err("Failed to load UTF-8 module\n");
> +		return ret;
> +	}
>  
>  	return 0;
>  }
>  
> -struct unicode_map *unicode_load(const char *version)
> +void unicode_register(struct unicode_ops *ops)
>  {
> -	struct unicode_map *um = NULL;
> -	int unicode_version;
> -
> -	if (version) {
> -		unsigned int maj, min, rev;
> -
> -		if (unicode_parse_version(version, &maj, &min, &rev) < 0)
> -			return ERR_PTR(-EINVAL);
> -
> -		if (!utf8version_is_supported(maj, min, rev))
> -			return ERR_PTR(-EINVAL);
> -
> -		unicode_version = UNICODE_AGE(maj, min, rev);
> -	} else {
> -		unicode_version = utf8version_latest();
> -		printk(KERN_WARNING"UTF-8 version not specified. "
> -		       "Assuming latest supported version (%d.%d.%d).",
> -		       (unicode_version >> 16) & 0xff,
> -		       (unicode_version >> 8) & 0xff,
> -		       (unicode_version & 0xff));
> -	}
> -
> -	um = kzalloc(sizeof(struct unicode_map), GFP_KERNEL);
> -	if (!um)
> -		return ERR_PTR(-ENOMEM);
> -
> -	um->charset = "UTF-8";
> -	um->version = unicode_version;
> -
> -	return um;
> +	utf8_ops = ops;
>  }
> -EXPORT_SYMBOL(unicode_load);
> +EXPORT_SYMBOL(unicode_register);
>  
> -void unicode_unload(struct unicode_map *um)
> +void unicode_unregister(void)
>  {
> -	kfree(um);
> +	utf8_ops = NULL;
>  }
> -EXPORT_SYMBOL(unicode_unload);
> +EXPORT_SYMBOL(unicode_unregister);
>  
>  MODULE_LICENSE("GPL v2");
> diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
> new file mode 100644
> index 000000000000..009faa68330c
> --- /dev/null
> +++ b/fs/unicode/utf8-core.c
> @@ -0,0 +1,112 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/string.h>
> +#include <linux/slab.h>
> +#include <linux/parser.h>
> +#include <linux/errno.h>
> +#include <linux/unicode.h>
> +#include <linux/stringhash.h>
> +#include <linux/delay.h>
> +
> +struct unicode_ops *utf8_ops;
> +
> +static int unicode_load_module(void);
> +
> +int unicode_validate(const struct unicode_map *um, const struct qstr *str)
> +{
> +	return utf8_ops->validate(um, str);
> +}
> +EXPORT_SYMBOL(unicode_validate);
> +
> +int unicode_strncmp(const struct unicode_map *um,
> +		    const struct qstr *s1, const struct qstr *s2)
> +{
> +	return utf8_ops->strncmp(um, s1, s2);
> +}
> +EXPORT_SYMBOL(unicode_strncmp);

I'm confused now.  Isn't this redefining unicode_strncmp ?  It was
defined in unicode_core.c on the hunk above and now it is redefined on
utf8_core.c.  There is something odd here.

> +
> +int unicode_strncasecmp(const struct unicode_map *um,
> +			const struct qstr *s1, const struct qstr *s2)
> +{
> +	return utf8_ops->strncasecmp(um, s1, s2);
> +}
> +EXPORT_SYMBOL(unicode_strncasecmp);
> +
> +/* String cf is expected to be a valid UTF-8 casefolded
> + * string.
> + */
> +int unicode_strncasecmp_folded(const struct unicode_map *um,
> +			       const struct qstr *cf,
> +			       const struct qstr *s1)
> +{
> +	return utf8_ops->strncasecmp_folded(um, cf, s1);
> +}
> +EXPORT_SYMBOL(unicode_strncasecmp_folded);
> +
> +int unicode_casefold(const struct unicode_map *um, const struct qstr *str,
> +		     unsigned char *dest, size_t dlen)
> +{
> +	return utf8_ops->casefold(um, str, dest, dlen);
> +}
> +EXPORT_SYMBOL(unicode_casefold);
> +
> +int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
> +			  struct qstr *str)
> +{
> +	return utf8_ops->casefold_hash(um, salt, str);
> +}
> +EXPORT_SYMBOL(unicode_casefold_hash);
> +
> +int unicode_normalize(const struct unicode_map *um, const struct qstr *str,
> +		      unsigned char *dest, size_t dlen)
> +{
> +	return utf8_ops->normalize(um, str, dest, dlen);
> +}
> +EXPORT_SYMBOL(unicode_normalize);
> +
> +struct unicode_map *unicode_load(const char *version)
> +{
> +	int ret = unicode_load_module();
> +
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	else
> +		return utf8_ops->load(version);
> +}
> +EXPORT_SYMBOL(unicode_load);
> +
> +void unicode_unload(struct unicode_map *um)
> +{
> +	kfree(um);
> +}
> +EXPORT_SYMBOL(unicode_unload);
> +
> +void unicode_register(struct unicode_ops *ops)
> +{
> +	utf8_ops = ops;
> +}
> +EXPORT_SYMBOL(unicode_register);
> +
> +void unicode_unregister(void)
> +{
> +	utf8_ops = NULL;
> +}
> +EXPORT_SYMBOL(unicode_unregister);
> +
> +static int unicode_load_module(void)
> +{
> +	int ret = request_module("utf8");
> +
> +	msleep(100);
> +
> +	if (ret) {
> +		pr_err("Failed to load UTF-8 module\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +MODULE_LICENSE("GPL v2");
> diff --git a/fs/unicode/utf8mod.c b/fs/unicode/utf8mod.c
> new file mode 100644
> index 000000000000..8eaeeb27255c
> --- /dev/null
> +++ b/fs/unicode/utf8mod.c
> @@ -0,0 +1,246 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/string.h>
> +#include <linux/slab.h>
> +#include <linux/parser.h>
> +#include <linux/errno.h>
> +#include <linux/unicode.h>
> +#include <linux/stringhash.h>
> +
> +#include "utf8n.h"
> +
> +static int utf8_validate(const struct unicode_map *um, const struct qstr *str)
> +{
> +	const struct utf8data *data = utf8nfdi(um->version);
> +
> +	if (utf8nlen(data, str->name, str->len) < 0)
> +		return -1;
> +	return 0;
> +}
> +
> +static int utf8_strncmp(const struct unicode_map *um,
> +			const struct qstr *s1, const struct qstr *s2)
> +{
> +	const struct utf8data *data = utf8nfdi(um->version);
> +	struct utf8cursor cur1, cur2;
> +	int c1, c2;
> +
> +	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
> +		return -EINVAL;
> +
> +	if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
> +		return -EINVAL;
> +
> +	do {
> +		c1 = utf8byte(&cur1);
> +		c2 = utf8byte(&cur2);
> +
> +		if (c1 < 0 || c2 < 0)
> +			return -EINVAL;
> +		if (c1 != c2)
> +			return 1;
> +	} while (c1);
> +
> +	return 0;
> +}
> +
> +static int utf8_strncasecmp(const struct unicode_map *um,
> +			    const struct qstr *s1, const struct qstr *s2)
> +{
> +	const struct utf8data *data = utf8nfdicf(um->version);
> +	struct utf8cursor cur1, cur2;
> +	int c1, c2;
> +
> +	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
> +		return -EINVAL;
> +
> +	if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
> +		return -EINVAL;
> +
> +	do {
> +		c1 = utf8byte(&cur1);
> +		c2 = utf8byte(&cur2);
> +
> +		if (c1 < 0 || c2 < 0)
> +			return -EINVAL;
> +		if (c1 != c2)
> +			return 1;
> +	} while (c1);
> +
> +	return 0;
> +}
> +
> +/* String cf is expected to be a valid UTF-8 casefolded
> + * string.
> + */
> +static int utf8_strncasecmp_folded(const struct unicode_map *um,
> +				   const struct qstr *cf,
> +				   const struct qstr *s1)
> +{
> +	const struct utf8data *data = utf8nfdicf(um->version);
> +	struct utf8cursor cur1;
> +	int c1, c2;
> +	int i = 0;
> +
> +	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
> +		return -EINVAL;
> +
> +	do {
> +		c1 = utf8byte(&cur1);
> +		c2 = cf->name[i++];
> +		if (c1 < 0)
> +			return -EINVAL;
> +		if (c1 != c2)
> +			return 1;
> +	} while (c1);
> +
> +	return 0;
> +}
> +
> +static int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
> +			 unsigned char *dest, size_t dlen)
> +{
> +	const struct utf8data *data = utf8nfdicf(um->version);
> +	struct utf8cursor cur;
> +	size_t nlen = 0;
> +
> +	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
> +		return -EINVAL;
> +
> +	for (nlen = 0; nlen < dlen; nlen++) {
> +		int c = utf8byte(&cur);
> +
> +		dest[nlen] = c;
> +		if (!c)
> +			return nlen;
> +		if (c == -1)
> +			break;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int utf8_casefold_hash(const struct unicode_map *um, const void *salt,
> +			      struct qstr *str)
> +{
> +	const struct utf8data *data = utf8nfdicf(um->version);
> +	struct utf8cursor cur;
> +	int c;
> +	unsigned long hash = init_name_hash(salt);
> +
> +	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
> +		return -EINVAL;
> +
> +	while ((c = utf8byte(&cur))) {
> +		if (c < 0)
> +			return -EINVAL;
> +		hash = partial_name_hash((unsigned char)c, hash);
> +	}
> +	str->hash = end_name_hash(hash);
> +	return 0;
> +}
> +
> +static int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
> +			  unsigned char *dest, size_t dlen)
> +{
> +	const struct utf8data *data = utf8nfdi(um->version);
> +	struct utf8cursor cur;
> +	ssize_t nlen = 0;
> +
> +	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
> +		return -EINVAL;
> +
> +	for (nlen = 0; nlen < dlen; nlen++) {
> +		int c = utf8byte(&cur);
> +
> +		dest[nlen] = c;
> +		if (!c)
> +			return nlen;
> +		if (c == -1)
> +			break;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int utf8_parse_version(const char *version, unsigned int *maj,
> +			      unsigned int *min, unsigned int *rev)
> +{
> +	substring_t args[3];
> +	char version_string[12];
> +	static const struct match_token token[] = {
> +		{1, "%d.%d.%d"},
> +		{0, NULL}
> +	};
> +
> +	strncpy(version_string, version, sizeof(version_string));
> +
> +	if (match_token(version_string, token, args) != 1)
> +		return -EINVAL;
> +
> +	if (match_int(&args[0], maj) || match_int(&args[1], min) ||
> +	    match_int(&args[2], rev))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static struct unicode_map *utf8_load(const char *version)
> +{
> +	struct unicode_map *um = NULL;
> +	int unicode_version;
> +
> +	if (version) {
> +		unsigned int maj, min, rev;
> +
> +		if (utf8_parse_version(version, &maj, &min, &rev) < 0)
> +			return ERR_PTR(-EINVAL);
> +
> +		if (!utf8version_is_supported(maj, min, rev))
> +			return ERR_PTR(-EINVAL);
> +
> +		unicode_version = UNICODE_AGE(maj, min, rev);
> +	} else {
> +		unicode_version = utf8version_latest();
> +		printk(KERN_WARNING"UTF-8 version not specified. "
> +		       "Assuming latest supported version (%d.%d.%d).",
> +		       (unicode_version >> 16) & 0xff,
> +		       (unicode_version >> 8) & 0xff,
> +		       (unicode_version & 0xff));
> +	}
> +
> +	um = kzalloc(sizeof(struct unicode_map), GFP_KERNEL);
> +	if (!um)
> +		return ERR_PTR(-ENOMEM);
> +
> +	um->charset = "UTF-8";
> +	um->version = unicode_version;
> +
> +	return um;
> +}
> +
> +static struct unicode_ops ops = {
> +	.validate = utf8_validate,
> +	.strncmp = utf8_strncmp,
> +	.strncasecmp = utf8_strncasecmp,
> +	.strncasecmp_folded = utf8_strncasecmp_folded,
> +	.casefold = utf8_casefold,
> +	.casefold_hash = utf8_casefold_hash,
> +	.normalize = utf8_normalize,
> +	.load = utf8_load,
> +};
> +
> +static int __init utf8_init(void)
> +{
> +	unicode_register(&ops);
> +	return 0;
> +}
> +
> +static void __exit utf8_exit(void)
> +{
> +	unicode_unregister();
> +}
> +
> +module_init(utf8_init);
> +module_exit(utf8_exit);
> +
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/unicode.h b/include/linux/unicode.h
> index de23f9ee720b..b0d59069e438 100644
> --- a/include/linux/unicode.h
> +++ b/include/linux/unicode.h
> @@ -10,6 +10,23 @@ struct unicode_map {
>  	int version;
>  };
>  
> +struct unicode_ops {
> +	int (*validate)(const struct unicode_map *um, const struct qstr *str);
> +	int (*strncmp)(const struct unicode_map *um, const struct qstr *s1,
> +		       const struct qstr *s2);
> +	int (*strncasecmp)(const struct unicode_map *um, const struct qstr *s1,
> +			   const struct qstr *s2);
> +	int (*strncasecmp_folded)(const struct unicode_map *um, const struct qstr *cf,
> +				  const struct qstr *s1);
> +	int (*normalize)(const struct unicode_map *um, const struct qstr *str,
> +			 unsigned char *dest, size_t dlen);
> +	int (*casefold)(const struct unicode_map *um, const struct qstr *str,
> +			unsigned char *dest, size_t dlen);
> +	int (*casefold_hash)(const struct unicode_map *um, const void *salt,
> +			     struct qstr *str);
> +	struct unicode_map* (*load)(const char *version);
> +};

Also, make sure you run checkpatch.pl on the patch series before
submitting. 

> +
>  int unicode_validate(const struct unicode_map *um, const struct qstr *str);
>  
>  int unicode_strncmp(const struct unicode_map *um,
> @@ -33,4 +50,7 @@ int unicode_casefold_hash(const struct unicode_map *um, const void *salt,
>  struct unicode_map *unicode_load(const char *version);
>  void unicode_unload(struct unicode_map *um);
>  
> +void unicode_register(struct unicode_ops *ops);
> +void unicode_unregister(void);
> +
>  #endif /* _LINUX_UNICODE_H */

-- 
Gabriel Krisman Bertazi