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Date:   Mon, 06 Sep 2021 18:13:54 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Shreeya Patel <shreeya.patel@...labora.com>,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH 05/11] unicode: pass a UNICODE_AGE() tripple to utf8_load

Christoph Hellwig <hch@....de> writes:

> Don't bother with pointless string parsing when the caller can just pass
> the version in the format that the core expects.  Also remove the
> fallback to the latest version that none of the callers actually uses.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/ext4/super.c            | 10 ++++----
>  fs/f2fs/super.c            | 10 ++++----
>  fs/unicode/utf8-core.c     | 50 ++++----------------------------------
>  fs/unicode/utf8-norm.c     | 11 ++-------
>  fs/unicode/utf8-selftest.c | 15 ++++++------
>  fs/unicode/utf8n.h         | 14 ++---------
>  include/linux/unicode.h    | 11 ++++++++-
>  7 files changed, 37 insertions(+), 84 deletions(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index a68be582bba5..be418a30b52e 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2016,9 +2016,9 @@ static const struct mount_opts {
>  static const struct ext4_sb_encodings {
>  	__u16 magic;
>  	char *name;
> -	char *version;
> +	unsigned int version;
>  } ext4_sb_encoding_map[] = {
> -	{EXT4_ENC_UTF8_12_1, "utf8", "12.1.0"},
> +	{EXT4_ENC_UTF8_12_1, "utf8", UNICODE_AGE(12, 1, 0)},
>  };
>  
>  static const struct ext4_sb_encodings *
> @@ -4308,15 +4308,15 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  		encoding = utf8_load(encoding_info->version);
>  		if (IS_ERR(encoding)) {
>  			ext4_msg(sb, KERN_ERR,
> -				 "can't mount with superblock charset: %s-%s "
> +				 "can't mount with superblock charset: %s-0x%x "
>  				 "not supported by the kernel. flags: 0x%x.",
>  				 encoding_info->name, encoding_info->version,
>  				 encoding_flags);
>  			goto failed_mount;

"Using encoding defined by superblock: utf8-0xc0100 with flags 0x0"

This is much less readable than what we previously had:

"Using encoding defined by superblock: utf8-12.1.0 with flags 0x0"

It is minor, but can we do instead:

ext4_msg("... %u.%u.%u\n", (encoding_info->version>>12) & 0xff,
	 (encoding_info->version>>8) & 0xff), encoding_info->version & 0xff))

The rest of the series looks good and I can pick it up for 5.15, unless
someone has anything else to say?  It has lived on the list for a while
now.

>  		}
>  		ext4_msg(sb, KERN_INFO,"Using encoding defined by superblock: "
> -			 "%s-%s with flags 0x%hx", encoding_info->name,
> -			 encoding_info->version?:"\b", encoding_flags);
> +			 "%s-0x%x with flags 0x%hx", encoding_info->name,
> +			 encoding_info->version, encoding_flags);
>  
>  		sb->s_encoding = encoding;
>  		sb->s_encoding_flags = encoding_flags;
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index af63ae009582..d107480f88a3 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -255,9 +255,9 @@ void f2fs_printk(struct f2fs_sb_info *sbi, const char *fmt, ...)
>  static const struct f2fs_sb_encodings {
>  	__u16 magic;
>  	char *name;
> -	char *version;
> +	unsigned int version;
>  } f2fs_sb_encoding_map[] = {
> -	{F2FS_ENC_UTF8_12_1, "utf8", "12.1.0"},
> +	{F2FS_ENC_UTF8_12_1, "utf8", UNICODE_AGE(12, 1, 0)},
>  };
>  
>  static const struct f2fs_sb_encodings *
> @@ -3734,15 +3734,15 @@ static int f2fs_setup_casefold(struct f2fs_sb_info *sbi)
>  		encoding = utf8_load(encoding_info->version);
>  		if (IS_ERR(encoding)) {
>  			f2fs_err(sbi,
> -				 "can't mount with superblock charset: %s-%s "
> +				 "can't mount with superblock charset: %s-0x%x "
>  				 "not supported by the kernel. flags: 0x%x.",
>  				 encoding_info->name, encoding_info->version,
>  				 encoding_flags);
>  			return PTR_ERR(encoding);
>  		}
>  		f2fs_info(sbi, "Using encoding defined by superblock: "
> -			 "%s-%s with flags 0x%hx", encoding_info->name,
> -			 encoding_info->version?:"\b", encoding_flags);
> +			 "%s-0x%x with flags 0x%hx", encoding_info->name,
> +			 encoding_info->version, encoding_flags);
>  
>  		sbi->sb->s_encoding = encoding;
>  		sbi->sb->s_encoding_flags = encoding_flags;
> diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
> index 86f42a078d99..dca2865c3bee 100644
> --- a/fs/unicode/utf8-core.c
> +++ b/fs/unicode/utf8-core.c
> @@ -167,59 +167,19 @@ int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
>  	}
>  	return -EINVAL;
>  }
> -
>  EXPORT_SYMBOL(utf8_normalize);
>  
> -static int utf8_parse_version(const char *version, unsigned int *maj,
> -			      unsigned int *min, unsigned int *rev)
> +struct unicode_map *utf8_load(unsigned int version)
>  {
> -	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;
> +	struct unicode_map *um;
>  
> -	return 0;
> -}
> -
> -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));
> -	}
> +	if (!utf8version_is_supported(version))
> +		return ERR_PTR(-EINVAL);
>  
>  	um = kzalloc(sizeof(struct unicode_map), GFP_KERNEL);
>  	if (!um)
>  		return ERR_PTR(-ENOMEM);
> -	um->version = unicode_version;
> +	um->version = version;
>  	return um;
>  }
>  EXPORT_SYMBOL(utf8_load);
> diff --git a/fs/unicode/utf8-norm.c b/fs/unicode/utf8-norm.c
> index 1d2d2e5b906a..12abf89ae6ec 100644
> --- a/fs/unicode/utf8-norm.c
> +++ b/fs/unicode/utf8-norm.c
> @@ -15,13 +15,12 @@ struct utf8data {
>  #include "utf8data.h"
>  #undef __INCLUDED_FROM_UTF8NORM_C__
>  
> -int utf8version_is_supported(u8 maj, u8 min, u8 rev)
> +int utf8version_is_supported(unsigned int version)
>  {
>  	int i = ARRAY_SIZE(utf8agetab) - 1;
> -	unsigned int sb_utf8version = UNICODE_AGE(maj, min, rev);
>  
>  	while (i >= 0 && utf8agetab[i] != 0) {
> -		if (sb_utf8version == utf8agetab[i])
> +		if (version == utf8agetab[i])
>  			return 1;
>  		i--;
>  	}
> @@ -29,12 +28,6 @@ int utf8version_is_supported(u8 maj, u8 min, u8 rev)
>  }
>  EXPORT_SYMBOL(utf8version_is_supported);
>  
> -int utf8version_latest(void)
> -{
> -	return utf8vers;
> -}
> -EXPORT_SYMBOL(utf8version_latest);
> -
>  /*
>   * UTF-8 valid ranges.
>   *
> diff --git a/fs/unicode/utf8-selftest.c b/fs/unicode/utf8-selftest.c
> index 6fe8af7edccb..37f33890e012 100644
> --- a/fs/unicode/utf8-selftest.c
> +++ b/fs/unicode/utf8-selftest.c
> @@ -235,7 +235,7 @@ static void check_utf8_nfdicf(void)
>  static void check_utf8_comparisons(void)
>  {
>  	int i;
> -	struct unicode_map *table = utf8_load("12.1.0");
> +	struct unicode_map *table = utf8_load(UNICODE_AGE(12, 1, 0));
>  
>  	if (IS_ERR(table)) {
>  		pr_err("%s: Unable to load utf8 %d.%d.%d. Skipping.\n",
> @@ -269,18 +269,19 @@ static void check_utf8_comparisons(void)
>  static void check_supported_versions(void)
>  {
>  	/* Unicode 7.0.0 should be supported. */
> -	test(utf8version_is_supported(7, 0, 0));
> +	test(utf8version_is_supported(UNICODE_AGE(7, 0, 0)));
>  
>  	/* Unicode 9.0.0 should be supported. */
> -	test(utf8version_is_supported(9, 0, 0));
> +	test(utf8version_is_supported(UNICODE_AGE(9, 0, 0)));
>  
>  	/* Unicode 1x.0.0 (the latest version) should be supported. */
> -	test(utf8version_is_supported(latest_maj, latest_min, latest_rev));
> +	test(utf8version_is_supported(
> +		UNICODE_AGE(latest_maj, latest_min, latest_rev)));
>  
>  	/* Next versions don't exist. */
> -	test(!utf8version_is_supported(13, 0, 0));
> -	test(!utf8version_is_supported(0, 0, 0));
> -	test(!utf8version_is_supported(-1, -1, -1));
> +	test(!utf8version_is_supported(UNICODE_AGE(13, 0, 0)));
> +	test(!utf8version_is_supported(UNICODE_AGE(0, 0, 0)));
> +	test(!utf8version_is_supported(UNICODE_AGE(-1, -1, -1)));
>  }
>  
>  static int __init init_test_ucd(void)
> diff --git a/fs/unicode/utf8n.h b/fs/unicode/utf8n.h
> index 0acd530c2c79..85a7bebf6927 100644
> --- a/fs/unicode/utf8n.h
> +++ b/fs/unicode/utf8n.h
> @@ -11,19 +11,9 @@
>  #include <linux/export.h>
>  #include <linux/string.h>
>  #include <linux/module.h>
> +#include <linux/unicode.h>
>  
> -/* Encoding a unicode version number as a single unsigned int. */
> -#define UNICODE_MAJ_SHIFT		(16)
> -#define UNICODE_MIN_SHIFT		(8)
> -
> -#define UNICODE_AGE(MAJ, MIN, REV)			\
> -	(((unsigned int)(MAJ) << UNICODE_MAJ_SHIFT) |	\
> -	 ((unsigned int)(MIN) << UNICODE_MIN_SHIFT) |	\
> -	 ((unsigned int)(REV)))
> -
> -/* Highest unicode version supported by the data tables. */
> -extern int utf8version_is_supported(u8 maj, u8 min, u8 rev);
> -extern int utf8version_latest(void);
> +int utf8version_is_supported(unsigned int version);
>  
>  /*
>   * Look for the correct const struct utf8data for a unicode version.
> diff --git a/include/linux/unicode.h b/include/linux/unicode.h
> index 0744f81c4b5f..a5cc44a8f90c 100644
> --- a/include/linux/unicode.h
> +++ b/include/linux/unicode.h
> @@ -5,6 +5,15 @@
>  #include <linux/init.h>
>  #include <linux/dcache.h>
>  
> +/* Encoding a unicode version number as a single unsigned int. */
> +#define UNICODE_MAJ_SHIFT		(16)
> +#define UNICODE_MIN_SHIFT		(8)
> +
> +#define UNICODE_AGE(MAJ, MIN, REV)			\
> +	(((unsigned int)(MAJ) << UNICODE_MAJ_SHIFT) |	\
> +	 ((unsigned int)(MIN) << UNICODE_MIN_SHIFT) |	\
> +	 ((unsigned int)(REV)))
> +
>  struct unicode_map {
>  	unsigned int version;
>  };
> @@ -29,7 +38,7 @@ int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
>  int utf8_casefold_hash(const struct unicode_map *um, const void *salt,
>  		       struct qstr *str);
>  
> -struct unicode_map *utf8_load(const char *version);
> +struct unicode_map *utf8_load(unsigned int version);
>  void utf8_unload(struct unicode_map *um);
>  
>  #endif /* _LINUX_UNICODE_H */

-- 
Gabriel Krisman Bertazi

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