On Thu, Oct 17, 2024 at 06:14:16PM -0300, André Almeida wrote: > Enable casefold lookup in tmpfs, based on the encoding defined by > userspace. That means that instead of comparing byte per byte a file > name, it compares to a case-insensitive equivalent of the Unicode > string. > > * Dcache handling > > There's a special need when dealing with case-insensitive dentries. > First of all, we currently invalidated every negative casefold dentries. > That happens because currently VFS code has no proper support to deal > with that, giving that it could incorrectly reuse a previous filename > for a new file that has a casefold match. For instance, this could > happen: > > $ mkdir DIR > $ rm -r DIR > $ mkdir dir > $ ls > DIR/ > > And would be perceived as inconsistency from userspace point of view, > because even that we match files in a case-insensitive manner, we still > honor whatever is the initial filename. > > Along with that, tmpfs stores only the first equivalent name dentry used > in the dcache, preventing duplications of dentries in the dcache. The > d_compare() version for casefold files uses a normalized string, so the > filename under lookup will be compared to another normalized string for > the existing file, achieving a casefolded lookup. > > * Enabling casefold via mount options > > Most filesystems have their data stored in disk, so casefold option need > to be enabled when building a filesystem on a device (via mkfs). > However, as tmpfs is a RAM backed filesystem, there's no disk > information and thus no mkfs to store information about casefold. > > For tmpfs, create casefold options for mounting. Userspace can then > enable casefold support for a mount point using: > > $ mount -t tmpfs -o casefold=utf8-12.1.0 fs_name mount_dir/ > > Userspace must set what Unicode standard is aiming to. The available > options depends on what the kernel Unicode subsystem supports. > > And for strict encoding: > > $ mount -t tmpfs -o casefold=utf8-12.1.0,strict_encoding fs_name mount_dir/ > > Strict encoding means that tmpfs will refuse to create invalid UTF-8 > sequences. When this option is not enabled, any invalid sequence will be > treated as an opaque byte sequence, ignoring the encoding thus not being > able to be looked up in a case-insensitive way. > > * Check for casefold dirs on simple_lookup() > > On simple_lookup(), do not create dentries for casefold directories. > Currently, VFS does not support case-insensitive negative dentries and > can create inconsistencies in the filesystem. Prevent such dentries to > being created in the first place. > > Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxx> > --- > Changes from v7: > - Dropped patch "tmpfs: Always set simple_dentry_operations as dentry ops" > - Re-place generic_ci_validate_strict_name() before inode creation > > Changes from v4: > - Squash commit Check for casefold dirs on simple_lookup() here > - Fails to mount if strict_encoding is used without encoding > - tmpfs doesn't support fscrypt, so I dropped d_revalidate line > > Changes from v3: > - Simplified shmem_parse_opt_casefold() > - sb->s_d_op is set to shmem_ci_dentry_ops during mount time > - got rid of shmem_lookup(), modified simple_lookup() > > Changes from v2: > - simple_lookup() now sets d_ops > - reworked shmem_parse_opt_casefold() > - if `mount -o casefold` has no param, load latest UTF-8 version > - using (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir) when possible > --- > fs/libfs.c | 4 +++ > mm/shmem.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--- > 2 files changed, 119 insertions(+), 4 deletions(-) > > diff --git a/fs/libfs.c b/fs/libfs.c > index 7b290404c5f9901010ada2f921a214dbc94eb5fa..a168ece5cc61b74114f537f5b7b8a07f2d48b2aa 100644 > --- a/fs/libfs.c > +++ b/fs/libfs.c > @@ -77,6 +77,10 @@ struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned > return ERR_PTR(-ENAMETOOLONG); > if (!dentry->d_sb->s_d_op) > d_set_d_op(dentry, &simple_dentry_operations); > + > + if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) > + return NULL; > + > d_add(dentry, NULL); > return NULL; > } > diff --git a/mm/shmem.c b/mm/shmem.c > index 4f11b55063631976af81e4221c7366b768db6690..ea4eff41eef35c9c253092f39402db142baa741b 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -40,6 +40,7 @@ > #include <linux/fs_parser.h> > #include <linux/swapfile.h> > #include <linux/iversion.h> > +#include <linux/unicode.h> > #include "swap.h" > > static struct vfsmount *shm_mnt __ro_after_init; > @@ -123,6 +124,8 @@ struct shmem_options { > bool noswap; > unsigned short quota_types; > struct shmem_quota_limits qlimits; > + struct unicode_map *encoding; > + bool strict_encoding; I'm a bit confused here because there seem to be codepaths where access to these fields is guarded by IS_ENABLED(CONFIG_UNICODE) and then theres one where it's not. Can't you make this consistent so that all access and the definition of the members are guarded by CONFIG_UNICODE? > #define SHMEM_SEEN_BLOCKS 1 > #define SHMEM_SEEN_INODES 2 > #define SHMEM_SEEN_HUGE 4 > @@ -3570,6 +3573,9 @@ shmem_mknod(struct mnt_idmap *idmap, struct inode *dir, > struct inode *inode; > int error; > > + if (!generic_ci_validate_strict_name(dir, &dentry->d_name)) > + return -EINVAL; > + > inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, dev, VM_NORESERVE); > if (IS_ERR(inode)) > return PTR_ERR(inode); > @@ -3589,7 +3595,12 @@ shmem_mknod(struct mnt_idmap *idmap, struct inode *dir, > dir->i_size += BOGO_DIRENT_SIZE; > inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); > inode_inc_iversion(dir); > - d_instantiate(dentry, inode); > + > + if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) > + d_add(dentry, inode); > + else > + d_instantiate(dentry, inode); > + > dget(dentry); /* Extra count - pin the dentry in core */ > return error; > > @@ -3680,7 +3691,10 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir, > inc_nlink(inode); > ihold(inode); /* New dentry reference */ > dget(dentry); /* Extra pinning count for the created dentry */ > - d_instantiate(dentry, inode); > + if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) > + d_add(dentry, inode); > + else > + d_instantiate(dentry, inode); > out: > return ret; > } > @@ -3700,6 +3714,14 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry) > inode_inc_iversion(dir); > drop_nlink(inode); > dput(dentry); /* Undo the count from "create" - does all the work */ > + > + /* > + * For now, VFS can't deal with case-insensitive negative dentries, so > + * we invalidate them > + */ > + if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) > + d_invalidate(dentry); > + > return 0; > } > > @@ -3844,7 +3866,10 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir, > dir->i_size += BOGO_DIRENT_SIZE; > inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); > inode_inc_iversion(dir); > - d_instantiate(dentry, inode); > + if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) > + d_add(dentry, inode); > + else > + d_instantiate(dentry, inode); > dget(dentry); > return 0; > > @@ -4197,6 +4222,9 @@ enum shmem_param { > Opt_usrquota_inode_hardlimit, > Opt_grpquota_block_hardlimit, > Opt_grpquota_inode_hardlimit, > + Opt_casefold_version, > + Opt_casefold, > + Opt_strict_encoding, > }; > > static const struct constant_table shmem_param_enums_huge[] = { > @@ -4228,9 +4256,54 @@ const struct fs_parameter_spec shmem_fs_parameters[] = { > fsparam_string("grpquota_block_hardlimit", Opt_grpquota_block_hardlimit), > fsparam_string("grpquota_inode_hardlimit", Opt_grpquota_inode_hardlimit), > #endif > + fsparam_string("casefold", Opt_casefold_version), > + fsparam_flag ("casefold", Opt_casefold), > + fsparam_flag ("strict_encoding", Opt_strict_encoding), > {} > }; > > +#if IS_ENABLED(CONFIG_UNICODE) > +static int shmem_parse_opt_casefold(struct fs_context *fc, struct fs_parameter *param, > + bool latest_version) > +{ > + struct shmem_options *ctx = fc->fs_private; > + unsigned int version = UTF8_LATEST; > + struct unicode_map *encoding; > + char *version_str = param->string + 5; > + > + if (!latest_version) { > + if (strncmp(param->string, "utf8-", 5)) > + return invalfc(fc, "Only UTF-8 encodings are supported " > + "in the format: utf8-<version number>"); > + > + version = utf8_parse_version(version_str); > + if (version < 0) > + return invalfc(fc, "Invalid UTF-8 version: %s", version_str); > + } > + > + encoding = utf8_load(version); > + > + if (IS_ERR(encoding)) { > + return invalfc(fc, "Failed loading UTF-8 version: utf8-%u.%u.%u\n", > + unicode_major(version), unicode_minor(version), > + unicode_rev(version)); > + } > + > + pr_info("tmpfs: Using encoding : utf8-%u.%u.%u\n", > + unicode_major(version), unicode_minor(version), unicode_rev(version)); > + > + ctx->encoding = encoding; > + > + return 0; > +} > +#else > +static int shmem_parse_opt_casefold(struct fs_context *fc, struct fs_parameter *param, > + bool latest_version) > +{ > + return invalfc(fc, "tmpfs: Kernel not built with CONFIG_UNICODE\n"); > +} > +#endif > + > static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param) > { > struct shmem_options *ctx = fc->fs_private; > @@ -4389,6 +4462,13 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param) > "Group quota inode hardlimit too large."); > ctx->qlimits.grpquota_ihardlimit = size; > break; > + case Opt_casefold_version: > + return shmem_parse_opt_casefold(fc, param, false); > + case Opt_casefold: > + return shmem_parse_opt_casefold(fc, param, true); > + case Opt_strict_encoding: > + ctx->strict_encoding = true; > + break; > } > return 0; > > @@ -4618,6 +4698,11 @@ static void shmem_put_super(struct super_block *sb) > { > struct shmem_sb_info *sbinfo = SHMEM_SB(sb); > > +#if IS_ENABLED(CONFIG_UNICODE) > + if (sb->s_encoding) > + utf8_unload(sb->s_encoding); > +#endif > + > #ifdef CONFIG_TMPFS_QUOTA > shmem_disable_quotas(sb); > #endif > @@ -4628,6 +4713,14 @@ static void shmem_put_super(struct super_block *sb) > sb->s_fs_info = NULL; > } > > +#if IS_ENABLED(CONFIG_UNICODE) && defined(CONFIG_TMPFS) > +static const struct dentry_operations shmem_ci_dentry_ops = { > + .d_hash = generic_ci_d_hash, > + .d_compare = generic_ci_d_compare, > + .d_delete = always_delete_dentry, > +}; > +#endif > + > static int shmem_fill_super(struct super_block *sb, struct fs_context *fc) > { > struct shmem_options *ctx = fc->fs_private; > @@ -4662,9 +4755,25 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc) > } > sb->s_export_op = &shmem_export_ops; > sb->s_flags |= SB_NOSEC | SB_I_VERSION; > + > + if (!ctx->encoding && ctx->strict_encoding) { > + pr_err("tmpfs: strict_encoding option without encoding is forbidden\n"); > + error = -EINVAL; > + goto failed; > + } > + > +#if IS_ENABLED(CONFIG_UNICODE) > + if (ctx->encoding) { > + sb->s_encoding = ctx->encoding; > + sb->s_d_op = &shmem_ci_dentry_ops; > + if (ctx->strict_encoding) > + sb->s_encoding_flags = SB_ENC_STRICT_MODE_FL; > + } > +#endif > + > #else > sb->s_flags |= SB_NOUSER; > -#endif > +#endif /* CONFIG_TMPFS */ > sbinfo->max_blocks = ctx->blocks; > sbinfo->max_inodes = ctx->inodes; > sbinfo->free_ispace = sbinfo->max_inodes * BOGO_INODE_SIZE; > @@ -4938,6 +5047,8 @@ int shmem_init_fs_context(struct fs_context *fc) > ctx->uid = current_fsuid(); > ctx->gid = current_fsgid(); > > + ctx->encoding = NULL; > + > fc->fs_private = ctx; > fc->ops = &shmem_fs_context_ops; > return 0; > > -- > 2.47.0 >