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Message-ID: <20210823035150.h3dor7hanhzua7lh@kari-VirtualBox>
Date: Mon, 23 Aug 2021 06:51:50 +0300
From: Kari Argillander <kari.argillander@...il.com>
To: Pali Rohár <pali@...nel.org>
Cc: linux-fsdevel@...r.kernel.org,
linux-ntfs-dev@...ts.sourceforge.net, linux-cifs@...r.kernel.org,
jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
Jan Kara <jack@...e.cz>,
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
"Theodore Y . Ts'o" <tytso@....edu>,
Luis de Bethencourt <luisbg@...nel.org>,
Salah Triki <salah.triki@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Kleikamp <shaggy@...nel.org>,
Anton Altaparmakov <anton@...era.com>,
Pavel Machek <pavel@....cz>,
Marek Behún <marek.behun@....cz>,
Christoph Hellwig <hch@...radead.org>
Subject: Re: [RFC PATCH 01/20] fat: Fix iocharset=utf8 mount option
On Sun, Aug 08, 2021 at 06:24:34PM +0200, Pali Rohár wrote:
> Currently iocharset=utf8 mount option is broken and error is printed to
> dmesg when it is used. To use UTF-8 as iocharset, it is required to use
> utf8=1 mount option.
>
> Fix iocharset=utf8 mount option to use be equivalent to the utf8=1 mount
> option and remove printing error from dmesg.
>
> FAT by definition is case-insensitive but current Linux implementation is
> case-sensitive for non-ASCII characters when UTF-8 is used. This patch does
> not change this UTF-8 behavior. Only more comments in fat_utf8_strnicmp()
> function are added about it.
>
> After this patch iocharset=utf8 starts working, so there is no need to have
> separate config option FAT_DEFAULT_UTF8 as FAT_DEFAULT_IOCHARSET for utf8
> also starts working. So remove redundant config option FAT_DEFAULT_UTF8.
>
> Signed-off-by: Pali Rohár <pali@...nel.org>
> ---
> fs/fat/Kconfig | 15 ---------------
> fs/fat/dir.c | 17 +++++++----------
> fs/fat/fat.h | 22 ++++++++++++++++++++++
> fs/fat/inode.c | 28 +++++++++++-----------------
> fs/fat/namei_vfat.c | 26 +++++++++++++++++++-------
> 5 files changed, 59 insertions(+), 49 deletions(-)
>
> diff --git a/fs/fat/Kconfig b/fs/fat/Kconfig
> index 66532a71e8fd..a31594137d5e 100644
> --- a/fs/fat/Kconfig
> +++ b/fs/fat/Kconfig
> @@ -100,18 +100,3 @@ config FAT_DEFAULT_IOCHARSET
>
> Enable any character sets you need in File Systems/Native Language
> Support.
> -
> -config FAT_DEFAULT_UTF8
> - bool "Enable FAT UTF-8 option by default"
> - depends on VFAT_FS
> - default n
> - help
> - Set this if you would like to have "utf8" mount option set
> - by default when mounting FAT filesystems.
> -
> - Even if you say Y here can always disable UTF-8 for
> - particular mount by adding "utf8=0" to mount options.
> -
> - Say Y if you use UTF-8 encoding for file names, N otherwise.
> -
> - See <file:Documentation/filesystems/vfat.rst> for more information.
> diff --git a/fs/fat/dir.c b/fs/fat/dir.c
> index c4a274285858..49fe8dc6e5f0 100644
> --- a/fs/fat/dir.c
> +++ b/fs/fat/dir.c
> @@ -33,11 +33,6 @@
> #define FAT_MAX_UNI_CHARS ((MSDOS_SLOTS - 1) * 13 + 1)
> #define FAT_MAX_UNI_SIZE (FAT_MAX_UNI_CHARS * sizeof(wchar_t))
>
> -static inline unsigned char fat_tolower(unsigned char c)
> -{
> - return ((c >= 'A') && (c <= 'Z')) ? c+32 : c;
> -}
> -
> static inline loff_t fat_make_i_pos(struct super_block *sb,
> struct buffer_head *bh,
> struct msdos_dir_entry *de)
> @@ -258,10 +253,12 @@ static inline int fat_name_match(struct msdos_sb_info *sbi,
> if (a_len != b_len)
> return 0;
>
> - if (sbi->options.name_check != 's')
> - return !nls_strnicmp(sbi->nls_io, a, b, a_len);
> - else
> + if (sbi->options.name_check == 's')
> return !memcmp(a, b, a_len);
> + else if (sbi->options.utf8)
> + return !fat_utf8_strnicmp(a, b, a_len);
> + else
> + return !nls_strnicmp(sbi->nls_io, a, b, a_len);
> }
>
> enum { PARSE_INVALID = 1, PARSE_NOT_LONGNAME, PARSE_EOF, };
> @@ -384,7 +381,7 @@ static int fat_parse_short(struct super_block *sb,
> de->lcase & CASE_LOWER_BASE);
> if (chl <= 1) {
> if (!isvfat)
> - ptname[i] = nocase ? c : fat_tolower(c);
> + ptname[i] = nocase ? c : fat_ascii_to_lower(c);
> i++;
> if (c != ' ') {
> name_len = i;
> @@ -421,7 +418,7 @@ static int fat_parse_short(struct super_block *sb,
> if (chl <= 1) {
> k++;
> if (!isvfat)
> - ptname[i] = nocase ? c : fat_tolower(c);
> + ptname[i] = nocase ? c : fat_ascii_to_lower(c);
> i++;
> if (c != ' ') {
> name_len = i;
> diff --git a/fs/fat/fat.h b/fs/fat/fat.h
> index 02d4d4234956..0cd15fb3b042 100644
> --- a/fs/fat/fat.h
> +++ b/fs/fat/fat.h
> @@ -310,6 +310,28 @@ static inline void fatwchar_to16(__u8 *dst, const wchar_t *src, size_t len)
> #endif
> }
>
> +static inline unsigned char fat_ascii_to_lower(unsigned char c)
> +{
> + return ((c >= 'A') && (c <= 'Z')) ? c+32 : c;
> +}
> +
> +static inline int fat_utf8_strnicmp(const unsigned char *a,
> + const unsigned char *b,
> + int len)
> +{
> + int i;
> +
> + /*
> + * FIXME: UTF-8 doesn't provide FAT semantics
> + * Case-insensitive support is only for 7-bit ASCII characters
> + */
> + for (i = 0; i < len; i++) {
> + if (fat_ascii_to_lower(a[i]) != fat_ascii_to_lower(b[i]))
> + return 1;
> + }
> + return 0;
> +}
> +
> /* fat/cache.c */
> extern void fat_cache_inval_inode(struct inode *inode);
> extern int fat_get_cluster(struct inode *inode, int cluster,
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index de0c9b013a85..f8c8a739f8f0 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -957,7 +957,9 @@ static int fat_show_options(struct seq_file *m, struct dentry *root)
> /* strip "cp" prefix from displayed option */
> seq_printf(m, ",codepage=%s", &sbi->nls_disk->charset[2]);
> if (isvfat) {
> - if (sbi->nls_io)
> + if (opts->utf8)
> + seq_printf(m, ",iocharset=utf8");
checkpatch will probably warn you about this.
WARNING: Prefer seq_puts to seq_printf
> + else if (sbi->nls_io)
> seq_printf(m, ",iocharset=%s", sbi->nls_io->charset);
>
> switch (opts->shortname) {
> @@ -994,8 +996,6 @@ static int fat_show_options(struct seq_file *m, struct dentry *root)
> if (opts->nocase)
> seq_puts(m, ",nocase");
> } else {
> - if (opts->utf8)
> - seq_puts(m, ",utf8");
> if (opts->unicode_xlate)
> seq_puts(m, ",uni_xlate");
> if (!opts->numtail)
> @@ -1157,8 +1157,6 @@ static int parse_options(struct super_block *sb, char *options, int is_vfat,
> opts->errors = FAT_ERRORS_RO;
> *debug = 0;
>
> - opts->utf8 = IS_ENABLED(CONFIG_FAT_DEFAULT_UTF8) && is_vfat;
> -
> if (!options)
> goto out;
>
> @@ -1319,10 +1317,14 @@ static int parse_options(struct super_block *sb, char *options, int is_vfat,
> | VFAT_SFN_CREATE_WIN95;
> break;
> case Opt_utf8_no: /* 0 or no or false */
> - opts->utf8 = 0;
> + fat_reset_iocharset(opts);
> break;
> case Opt_utf8_yes: /* empty or 1 or yes or true */
> - opts->utf8 = 1;
> + fat_reset_iocharset(opts);
> + iocharset = kstrdup("utf8", GFP_KERNEL);
> + if (!iocharset)
> + return -ENOMEM;
> + opts->iocharset = iocharset;
> break;
> case Opt_uni_xl_no: /* 0 or no or false */
> opts->unicode_xlate = 0;
> @@ -1360,18 +1362,11 @@ static int parse_options(struct super_block *sb, char *options, int is_vfat,
> }
>
> out:
> - /* UTF-8 doesn't provide FAT semantics */
> - if (!strcmp(opts->iocharset, "utf8")) {
> - fat_msg(sb, KERN_WARNING, "utf8 is not a recommended IO charset"
> - " for FAT filesystems, filesystem will be "
> - "case sensitive!");
> - }
> + opts->utf8 = !strcmp(opts->iocharset, "utf8") && is_vfat;
>
> /* If user doesn't specify allow_utime, it's initialized from dmask. */
> if (opts->allow_utime == (unsigned short)-1)
> opts->allow_utime = ~opts->fs_dmask & (S_IWGRP | S_IWOTH);
> - if (opts->unicode_xlate)
> - opts->utf8 = 0;
> if (opts->nfs == FAT_NFS_NOSTALE_RO) {
> sb->s_flags |= SB_RDONLY;
> sb->s_export_op = &fat_export_ops_nostale;
> @@ -1832,8 +1827,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
> goto out_fail;
> }
>
> - /* FIXME: utf8 is using iocharset for upper/lower conversion */
> - if (sbi->options.isvfat) {
> + if (sbi->options.isvfat && !sbi->options.utf8) {
> sbi->nls_io = load_nls(sbi->options.iocharset);
> if (!sbi->nls_io) {
> fat_msg(sb, KERN_ERR, "IO charset %s not found",
> diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
> index 5369d82e0bfb..efb3cb9ea8a8 100644
> --- a/fs/fat/namei_vfat.c
> +++ b/fs/fat/namei_vfat.c
> @@ -134,6 +134,7 @@ static int vfat_hash(const struct dentry *dentry, struct qstr *qstr)
> static int vfat_hashi(const struct dentry *dentry, struct qstr *qstr)
> {
> struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
> + int utf8 = MSDOS_SB(dentry->d_sb)->options.utf8;
> const unsigned char *name;
> unsigned int len;
> unsigned long hash;
> @@ -142,8 +143,17 @@ static int vfat_hashi(const struct dentry *dentry, struct qstr *qstr)
> len = vfat_striptail_len(qstr);
>
> hash = init_name_hash(dentry);
> - while (len--)
> - hash = partial_name_hash(nls_tolower(t, *name++), hash);
> + if (utf8) {
> + /*
> + * FIXME: UTF-8 doesn't provide FAT semantics
> + * Case-insensitive support is only for 7-bit ASCII characters
> + */
> + while (len--)
> + hash = partial_name_hash(fat_ascii_to_lower(*name++), hash);
> + } else {
> + while (len--)
> + hash = partial_name_hash(nls_tolower(t, *name++), hash);
> + }
> qstr->hash = end_name_hash(hash);
>
> return 0;
> @@ -156,16 +166,18 @@ static int vfat_cmpi(const struct dentry *dentry,
> unsigned int len, const char *str, const struct qstr *name)
> {
> struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
> + int utf8 = MSDOS_SB(dentry->d_sb)->options.utf8;
> unsigned int alen, blen;
>
> /* A filename cannot end in '.' or we treat it like it has none */
> alen = vfat_striptail_len(name);
> blen = __vfat_striptail_len(len, str);
> - if (alen == blen) {
> - if (nls_strnicmp(t, name->name, str, alen) == 0)
> - return 0;
> - }
> - return 1;
> + if (alen != blen)
> + return 1;
> + else if (utf8)
> + return fat_utf8_strnicmp(name->name, str, alen);
> + else
> + return nls_strnicmp(t, name->name, str, alen);
> }
>
> /*
> --
> 2.20.1
>
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