Return-Path: Received: from userp2130.oracle.com ([156.151.31.86]:43142 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725840AbeJLF4S (ORCPT ); Fri, 12 Oct 2018 01:56:18 -0400 Date: Thu, 11 Oct 2018 15:26:39 -0700 From: "Darrick J. Wong" To: Gabriel Krisman Bertazi Cc: tytso@mit.edu, linux-ext4@vger.kernel.org Subject: Re: [PATCH RESEND v2 20/25] ext4: Include encoding information in the superblock Message-ID: <20181011222639.GC24099@magnolia> References: <20180924215655.3676-1-krisman@collabora.co.uk> <20180924215655.3676-21-krisman@collabora.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180924215655.3676-21-krisman@collabora.co.uk> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Sep 24, 2018 at 05:56:50PM -0400, Gabriel Krisman Bertazi wrote: > Support for encoding is considered an incompatible feature, since it has > potential to create collisions of file names in existing filesystems. > If the feature flag is not enabled, the entire filesystem will operate > on opaque byte sequences, respecting the original behavior. > > The charset data is encoded in a new field in the superblock using a > magic number specific to ext4. This is the easiest way I found to avoid > writing the name of the charset in the superblock. The magic number is > mapped to the exact NLS table, but the mapping is specific to ext4. > Since we don't have any commitment to support old encodings, the only > encodings I am supporting right now is utf8n-10.0.0 and ascii, both > using the NLS abstraction. > > 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. > > Changes since v1: > - Guard code with CONFIG_NLS. > - Use 16 bits for s_ioencoding. > - Split mount option from this patch > > Signed-off-by: Gabriel Krisman Bertazi > --- > fs/ext4/ext4.h | 19 ++++++++++++- > fs/ext4/super.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 91 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > index ac05bd86643a..6bdaba9c6923 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -1190,6 +1190,11 @@ extern void ext4_set_bits(void *bm, int cur, int len); > /* Metadata checksum algorithm codes */ > #define EXT4_CRC32C_CHKSUM 1 > > +/* Be careful when modifying these flags. The lower byte must match the > + * NLS flags. */ > + > +#define EXT4_ENC_NLS_FL_MASK 0x00FF > + > /* > * Structure of the super block > */ > @@ -1316,7 +1321,9 @@ struct ext4_super_block { > __u8 s_first_error_time_hi; > __u8 s_last_error_time_hi; > __u8 s_pad[2]; > - __le32 s_reserved[96]; /* Padding to the end of the block */ > + __le16 s_ioencoding; /* charset encoding */ > + __le16 s_ioencoding_flags; /* charset encoding flags */ > + __le32 s_reserved[95]; /* Padding to the end of the block */ Please update Documentation/filesystems/ext4/super.rst with this when it appears after the merge window. > __le32 s_checksum; /* crc32c(superblock) */ > }; > > @@ -1341,6 +1348,8 @@ struct ext4_super_block { > /* Number of quota types we support */ > #define EXT4_MAXQUOTAS 3 > > +struct ext4_sb_encodings; > + > /* > * fourth extended-fs super-block data in memory > */ > @@ -1390,6 +1399,11 @@ struct ext4_sb_info { > struct kobject s_kobj; > struct completion s_kobj_unregister; > struct super_block *s_sb; > +#ifdef CONFIG_NLS > + const struct ext4_sb_encodings *encoding_info; > + struct nls_table *encoding; > + __u16 encoding_flags; > +#endif > > /* Journaling */ > struct journal_s *s_journal; > @@ -1665,6 +1679,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei) > #define EXT4_FEATURE_INCOMPAT_LARGEDIR 0x4000 /* >2GB or 3-lvl htree */ > #define EXT4_FEATURE_INCOMPAT_INLINE_DATA 0x8000 /* data in inode */ > #define EXT4_FEATURE_INCOMPAT_ENCRYPT 0x10000 > +#define EXT4_FEATURE_INCOMPAT_IOENCODING 0x20000 /me wonders how the 'ioencoding' name came about? We're not encoding disk IO, just directory entries. > > #define EXT4_FEATURE_COMPAT_FUNCS(name, flagname) \ > static inline bool ext4_has_feature_##name(struct super_block *sb) \ > @@ -1753,6 +1768,7 @@ EXT4_FEATURE_INCOMPAT_FUNCS(csum_seed, CSUM_SEED) > EXT4_FEATURE_INCOMPAT_FUNCS(largedir, LARGEDIR) > EXT4_FEATURE_INCOMPAT_FUNCS(inline_data, INLINE_DATA) > EXT4_FEATURE_INCOMPAT_FUNCS(encrypt, ENCRYPT) > +EXT4_FEATURE_INCOMPAT_FUNCS(ioencoding, IOENCODING) > > #define EXT2_FEATURE_COMPAT_SUPP EXT4_FEATURE_COMPAT_EXT_ATTR > #define EXT2_FEATURE_INCOMPAT_SUPP (EXT4_FEATURE_INCOMPAT_FILETYPE| \ > @@ -1780,6 +1796,7 @@ EXT4_FEATURE_INCOMPAT_FUNCS(encrypt, ENCRYPT) > EXT4_FEATURE_INCOMPAT_MMP | \ > EXT4_FEATURE_INCOMPAT_INLINE_DATA | \ > EXT4_FEATURE_INCOMPAT_ENCRYPT | \ > + EXT4_FEATURE_INCOMPAT_IOENCODING | \ > EXT4_FEATURE_INCOMPAT_CSUM_SEED | \ > EXT4_FEATURE_INCOMPAT_LARGEDIR) > #define EXT4_FEATURE_RO_COMPAT_SUPP (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \ > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index a430fb3e9720..ccf4742fea3b 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -42,6 +42,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -1010,6 +1011,10 @@ static void ext4_put_super(struct super_block *sb) > crypto_free_shash(sbi->s_chksum_driver); > kfree(sbi->s_blockgroup_lock); > fs_put_dax(sbi->s_daxdev); > +#ifdef CONFIG_NLS > + unload_nls(sbi->encoding); > + kfree(sbi->encoding_info); > +#endif > kfree(sbi); > } > > @@ -1703,6 +1708,31 @@ static const struct mount_opts { > {Opt_err, 0, 0} > }; > > +#ifdef CONFIG_NLS > +static const struct ext4_sb_encodings { > + char *name; > + char *version; > +} ext4_sb_encoding_map[] = { > + /* 0x0 */ {"ascii", NULL}, > + /* 0x1 */ {"utf8", "10.0.0"}, > +}; > + > +static int > +ext4_sb_read_encoding(const struct ext4_super_block *es, > + const struct ext4_sb_encodings **encoding, __u16 *flags) > +{ > + __u16 magic = le16_to_cpu(es->s_ioencoding); > + > + if (magic >= ARRAY_SIZE(ext4_sb_encoding_map)) > + return -EINVAL; > + > + *encoding = &ext4_sb_encoding_map[magic]; > + *flags = le16_to_cpu(es->s_ioencoding_flags); > + > + return 0; > +} > +#endif > + > static int handle_mount_opt(struct super_block *sb, char *opt, int token, > substring_t *args, unsigned long *journal_devnum, > unsigned int *journal_ioprio, int is_remount) > @@ -3515,6 +3545,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) > int err = 0; > unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO; > ext4_group_t first_not_zeroed; > +#ifdef CONFIG_NLS > + struct nls_table *encoding; > + const struct ext4_sb_encodings *encoding_info; > + __u16 nls_flags; > +#endif > > if ((data && !orig_data) || !sbi) > goto out_free_base; > @@ -3687,6 +3722,39 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) > &journal_ioprio, 0)) > goto failed_mount; > > +#ifdef CONFIG_NLS > + if (ext4_has_feature_ioencoding(sb) && !sbi->encoding) { > + if (ext4_has_feature_encrypt(sb)) { > + ext4_msg(sb, KERN_ERR, > + "Can't mount with both encoding and encryption"); > + goto failed_mount; > + } > + > + if (ext4_sb_read_encoding(es, &encoding_info, &nls_flags)) { > + ext4_msg(sb, KERN_ERR, > + "Encoding requested by superblock is unknown"); > + goto failed_mount; > + } > + > + encoding = load_nls_version(encoding_info->name, > + encoding_info->version, > + nls_flags & EXT4_ENC_NLS_FL_MASK); > + if (IS_ERR(encoding)) { > + ext4_msg(sb, KERN_ERR, "can't mount with superblock charset: " > + "%s-%s not supported by the kernel. flags: 0x%x", > + encoding_info->name, encoding_info->version, > + nls_flags); > + goto failed_mount; > + } > + ext4_msg(sb, KERN_INFO,"Using encoding defined by superblock: " > + "%s-%s with flags 0x%hx", encoding_info->name, > + encoding_info->version?:"\b", nls_flags); > + > + sbi->encoding = encoding; > + sbi->encoding_flags = nls_flags; > + } > +#endif > + > if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) { > printk_once(KERN_WARNING "EXT4-fs: Warning: mounting " > "with data=journal disables delayed " > @@ -4527,6 +4595,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) > failed_mount: > if (sbi->s_chksum_driver) > crypto_free_shash(sbi->s_chksum_driver); > + > +#ifdef CONFIG_NLS > + unload_nls(sbi->encoding); > +#endif > + > #ifdef CONFIG_QUOTA > for (i = 0; i < EXT4_MAXQUOTAS; i++) > kfree(sbi->s_qf_names[i]); > -- > 2.19.0 >