Commit c843843e authored by Daniel Rosenberg's avatar Daniel Rosenberg Committed by Jaegeuk Kim
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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 the use of utf8_casefold_hash to
avoid an allocation.

By providing a common implementation, all users can benefit from any
optimizations without needing to port over improvements.

Signed-off-by: default avatarDaniel Rosenberg <drosen@google.com>
Reviewed-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent 3d7bfea8

fs/libfs.c

+87 −0
Original line number Diff line number Diff line
@@ -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 +1365,88 @@ 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.

 *

 * Return: if names will need casefolding

 */

static bool needs_casefold(const struct inode *dir)

{

	return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;

}



/**

 * 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 *dir = 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 (!dir || !needs_casefold(dir))

		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 of the parent directory

 * @str:	qstr of name whose hash we should fill in

 *

 * Return: 0 if hash was successful or unchanged, and -EINVAL on error

 */

int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)

{

	const struct inode *dir = READ_ONCE(dentry->d_inode);

	struct super_block *sb = dentry->d_sb;

	const struct unicode_map *um = sb->s_encoding;

	int ret = 0;



	if (!dir || !needs_casefold(dir))

		return 0;



	ret = utf8_casefold_hash(um, dentry, str);

	if (ret < 0 && sb_has_strict_encoding(sb))

		return -EINVAL;

	return 0;

}

EXPORT_SYMBOL(generic_ci_d_hash);

#endif

include/linux/fs.h

+16 −0
Original line number Diff line number Diff line
@@ -1371,6 +1371,12 @@ 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

 */
@@ -1440,6 +1446,10 @@ 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 */
@@ -3262,6 +3272,12 @@ 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 *,

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