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Message-Id: <20200707113123.3429337-3-drosen@google.com> Date: Tue, 7 Jul 2020 04:31:21 -0700 From: Daniel Rosenberg <drosen@...gle.com> To: "Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org, Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>, linux-f2fs-devel@...ts.sourceforge.net, Eric Biggers <ebiggers@...nel.org>, linux-fscrypt@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk> Cc: Andreas Dilger <adilger.kernel@...ger.ca>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, Gabriel Krisman Bertazi <krisman@...labora.com>, kernel-team@...roid.com, Daniel Rosenberg <drosen@...gle.com> Subject: [PATCH v10 2/4] fs: Add standard casefolding support This adds general supporting functions for filesystems that use utf8 casefolding. It provides standard dentry_operations and adds the necessary structures in struct super_block to allow this standardization. The new dentry operations are functionally equivalent to the existing operations in ext4 and f2fs, apart from ths use of utf8_casefold_hash to avoid an allocation, and dealing with casefolding and encryption. It doesn't make sense to casefold the no-key token for the encrypted name, so we don't casefold in that case. By providing a common implementation, all users can benefit from any optimizations without needing to port over improvements. Signed-off-by: Daniel Rosenberg <drosen@...gle.com> --- fs/libfs.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 16 ++++++++ 2 files changed, 112 insertions(+) diff --git a/fs/libfs.c b/fs/libfs.c index 4d08edf19c78..f7df13806f36 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -20,6 +20,8 @@ #include <linux/fs_context.h> #include <linux/pseudo_fs.h> #include <linux/fsnotify.h> +#include <linux/unicode.h> +#include <linux/fscrypt.h> #include <linux/uaccess.h> @@ -1363,3 +1365,97 @@ bool is_empty_dir_inode(struct inode *inode) return (inode->i_fop == &empty_dir_operations) && (inode->i_op == &empty_dir_inode_operations); } + +#ifdef CONFIG_UNICODE +/* + * Determine if the name of a dentry should be casefolded. It does not make + * sense to casefold the no-key token of an encrypted filename. + * + * Return: if names will need casefolding + */ +static bool needs_casefold(const struct inode *dir, const struct dentry *dentry) +{ + return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding && + !(dentry->d_flags & DCACHE_ENCRYPTED_NAME); +} + +/** + * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems + * @dentry: dentry whose name we are checking against + * @len: len of name of dentry + * @str: str pointer to name of dentry + * @name: Name to compare against + * + * Return: 0 if names match, 1 if mismatch, or -ERRNO + */ +int generic_ci_d_compare(const struct dentry *dentry, unsigned int len, + const char *str, const struct qstr *name) +{ + const struct dentry *parent = READ_ONCE(dentry->d_parent); + const struct inode *inode = READ_ONCE(parent->d_inode); + const struct super_block *sb = dentry->d_sb; + const struct unicode_map *um = sb->s_encoding; + struct qstr qstr = QSTR_INIT(str, len); + char strbuf[DNAME_INLINE_LEN]; + int ret; + + if (!inode || !needs_casefold(inode, dentry)) + goto fallback; + /* + * If the dentry name is stored in-line, then it may be concurrently + * modified by a rename. If this happens, the VFS will eventually retry + * the lookup, so it doesn't matter what ->d_compare() returns. + * However, it's unsafe to call utf8_strncasecmp() with an unstable + * string. Therefore, we have to copy the name into a temporary buffer. + */ + if (len <= DNAME_INLINE_LEN - 1) { + memcpy(strbuf, str, len); + strbuf[len] = 0; + qstr.name = strbuf; + /* prevent compiler from optimizing out the temporary buffer */ + barrier(); + } + ret = utf8_strncasecmp(um, name, &qstr); + if (ret >= 0) + return ret; + + if (sb_has_strict_encoding(sb)) + return -EINVAL; +fallback: + if (len != name->len) + return 1; + return !!memcmp(str, name->name, len); +} +EXPORT_SYMBOL(generic_ci_d_compare); + +/** + * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems + * @dentry: dentry whose name we are hashing + * @str: qstr of name whose hash we should fill in + * + * Return: 0 if hash was successful, or -ERRNO + */ +int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str) +{ + const struct inode *inode = READ_ONCE(dentry->d_inode); + struct super_block *sb = dentry->d_sb; + const struct unicode_map *um = sb->s_encoding; + int ret = 0; + + if (!inode || !needs_casefold(inode, dentry)) + return 0; + + ret = utf8_casefold_hash(um, dentry, str); + if (ret < 0) + goto err; + + return 0; +err: + if (sb_has_strict_encoding(sb)) + ret = -EINVAL; + else + ret = 0; + return ret; +} +EXPORT_SYMBOL(generic_ci_d_hash); +#endif diff --git a/include/linux/fs.h b/include/linux/fs.h index 3f881a892ea7..af8f2ecec8ff 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1392,6 +1392,12 @@ extern int send_sigurg(struct fown_struct *fown); #define SB_ACTIVE (1<<30) #define SB_NOUSER (1<<31) +/* These flags relate to encoding and casefolding */ +#define SB_ENC_STRICT_MODE_FL (1 << 0) + +#define sb_has_strict_encoding(sb) \ + (sb->s_encoding_flags & SB_ENC_STRICT_MODE_FL) + /* * Umount options */ @@ -1461,6 +1467,10 @@ struct super_block { #endif #ifdef CONFIG_FS_VERITY const struct fsverity_operations *s_vop; +#endif +#ifdef CONFIG_UNICODE + struct unicode_map *s_encoding; + __u16 s_encoding_flags; #endif struct hlist_bl_head s_roots; /* alternate root dentries for NFS */ struct list_head s_mounts; /* list of mounts; _not_ for fs use */ @@ -3385,6 +3395,12 @@ extern int generic_file_fsync(struct file *, loff_t, loff_t, int); extern int generic_check_addressable(unsigned, u64); +#ifdef CONFIG_UNICODE +extern int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str); +extern int generic_ci_d_compare(const struct dentry *dentry, unsigned int len, + const char *str, const struct qstr *name); +#endif + #ifdef CONFIG_MIGRATION extern int buffer_migrate_page(struct address_space *, struct page *, struct page *, -- 2.27.0.212.ge8ba1cc988-goog
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