Commit c843843e authored by Daniel Rosenberg's avatar Daniel Rosenberg Committed by Jaegeuk Kim

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
......@@ -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
......@@ -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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