Eugen Hristev <eugen.hris...@collabora.com> writes: > On 2/16/24 18:12, Gabriel Krisman Bertazi wrote: >> Eugen Hristev <eugen.hris...@collabora.com> writes: >> >>> From: Gabriel Krisman Bertazi <kris...@collabora.com> >>> >>> generic_ci_match can be used by case-insensitive filesystems to compare >>> strings under lookup with dirents in a case-insensitive way. This >>> function is currently reimplemented by each filesystem supporting >>> casefolding, so this reduces code duplication in filesystem-specific >>> code. >>> >>> Signed-off-by: Gabriel Krisman Bertazi <kris...@collabora.com> >>> [eugen.hris...@collabora.com: rework to first test the exact match] >>> Signed-off-by: Eugen Hristev <eugen.hris...@collabora.com> >>> --- >>> fs/libfs.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++ >>> include/linux/fs.h | 4 +++ >>> 2 files changed, 84 insertions(+) >>> >>> diff --git a/fs/libfs.c b/fs/libfs.c >>> index bb18884ff20e..82871fa1b066 100644 >>> --- a/fs/libfs.c >>> +++ b/fs/libfs.c >>> @@ -1773,6 +1773,86 @@ static const struct dentry_operations >>> generic_ci_dentry_ops = { >>> .d_hash = generic_ci_d_hash, >>> .d_compare = generic_ci_d_compare, >>> }; >>> + >>> +/** >>> + * generic_ci_match() - Match a name (case-insensitively) with a dirent. >>> + * This is a filesystem helper for comparison with directory entries. >>> + * generic_ci_d_compare should be used in VFS' ->d_compare instead. >>> + * >>> + * @parent: Inode of the parent of the dirent under comparison >>> + * @name: name under lookup. >>> + * @folded_name: Optional pre-folded name under lookup >>> + * @de_name: Dirent name. >>> + * @de_name_len: dirent name length. >>> + * >>> + * >> >> Since this need a respin, mind dropping the extra empty line here? >> >>> + * Test whether a case-insensitive directory entry matches the filename >>> + * being searched. If @folded_name is provided, it is used instead of >>> + * recalculating the casefold of @name. >>> + * >>> + * Return: > 0 if the directory entry matches, 0 if it doesn't match, or >>> + * < 0 on error. >>> + */ >>> +int generic_ci_match(const struct inode *parent, >>> + const struct qstr *name, >>> + const struct qstr *folded_name, >>> + const u8 *de_name, u32 de_name_len) >>> +{ >>> + const struct super_block *sb = parent->i_sb; >>> + const struct unicode_map *um = sb->s_encoding; >>> + struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len); >>> + struct qstr dirent = QSTR_INIT(de_name, de_name_len); >>> + int res; >>> + >>> + if (IS_ENCRYPTED(parent)) { >>> + const struct fscrypt_str encrypted_name = >>> + FSTR_INIT((u8 *) de_name, de_name_len); >>> + >>> + if (WARN_ON_ONCE(!fscrypt_has_encryption_key(parent))) >>> + return -EINVAL; >>> + >>> + decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL); >>> + if (!decrypted_name.name) >>> + return -ENOMEM; >>> + res = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name, >>> + &decrypted_name); >>> + if (res < 0) >>> + goto out; >>> + dirent.name = decrypted_name.name; >>> + dirent.len = decrypted_name.len; >>> + } >>> + >>> + /* >>> + * Attempt a case-sensitive match first. It is cheaper and >>> + * should cover most lookups, including all the sane >>> + * applications that expect a case-sensitive filesystem. >>> + * >> >> >>> + * This comparison is safe under RCU because the caller >>> + * guarantees the consistency between str and len. See >>> + * __d_lookup_rcu_op_compare() for details. >>> + */ >> >> This paragraph doesn't really make sense here. It is originally from >> the d_compare hook, which can be called under RCU, but there is no RCU >> here. Also, here we are comparing the dirent with the >> name-under-lookup, name which is already safe. >> >> >>> + if (folded_name->name) { >>> + if (dirent.len == folded_name->len && >>> + !memcmp(folded_name->name, dirent.name, dirent.len)) { >>> + res = 1; >>> + goto out; >>> + } >>> + res = !utf8_strncasecmp_folded(um, folded_name, &dirent); >> >> Hmm, second thought on this. This will ignore errors from utf8_strncasecmp*, >> which CAN happen for the first time here, if the dirent itself is >> corrupted on disk (exactly why we have patch 6). Yes, ext4_match will drop >> the >> error, but we want to propagate it from here, such that the warning on >> patch 6 can trigger. >> >> This is why I did that match dance on the original submission. Sorry >> for suggesting it. We really want to get the error from utf8 and >> propagate it if it is negative. basically: >> >> res > 0: match >> res == 0: no match. >> res < 0: propagate error and let the caller handle it > > In that case I will revert to the original v9 implementation and send a v11 to > handle that.
Please, note that the memcmp optimization is still valid. On match, we know the name is valid utf8. It is just a matter of propagating the error code from utf8 to the caller if we need to call it. -- Gabriel Krisman Bertazi _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel