Commit d72d1ce6 authored by Gao Xiang's avatar Gao Xiang Committed by Greg Kroah-Hartman

staging: erofs: add namei functions

This commit adds functions that transfer names to inodes.
Signed-off-by: default avatarMiao Xie <miaoxie@huawei.com>
Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarGao Xiang <gaoxiang25@huawei.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3aa8ec71
// SPDX-License-Identifier: GPL-2.0
/*
* linux/drivers/staging/erofs/namei.c
*
* Copyright (C) 2017-2018 HUAWEI, Inc.
* http://www.huawei.com/
* Created by Gao Xiang <gaoxiang25@huawei.com>
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of the Linux
* distribution for more details.
*/
#include "internal.h"
/* based on the value of qn->len is accurate */
static inline int dirnamecmp(struct qstr *qn,
struct qstr *qd, unsigned *matched)
{
unsigned i = *matched, len = min(qn->len, qd->len);
loop:
if (unlikely(i >= len)) {
*matched = i;
if (qn->len < qd->len) {
/*
* actually (qn->len == qd->len)
* when qd->name[i] == '\0'
*/
return qd->name[i] == '\0' ? 0 : -1;
}
return (qn->len > qd->len);
}
if (qn->name[i] != qd->name[i]) {
*matched = i;
return qn->name[i] > qd->name[i] ? 1 : -1;
}
++i;
goto loop;
}
static struct erofs_dirent *find_target_dirent(
struct qstr *name,
u8 *data, int maxsize)
{
unsigned ndirents, head, back;
unsigned startprfx, endprfx;
struct erofs_dirent *const de = (struct erofs_dirent *)data;
/* make sure that maxsize is valid */
BUG_ON(maxsize < sizeof(struct erofs_dirent));
ndirents = le16_to_cpu(de->nameoff) / sizeof(*de);
/* corrupted dir (may be unnecessary...) */
BUG_ON(!ndirents);
head = 0;
back = ndirents - 1;
startprfx = endprfx = 0;
while (head <= back) {
unsigned mid = head + (back - head) / 2;
unsigned nameoff = le16_to_cpu(de[mid].nameoff);
unsigned matched = min(startprfx, endprfx);
struct qstr dname = QSTR_INIT(data + nameoff,
unlikely(mid >= ndirents - 1) ?
maxsize - nameoff :
le16_to_cpu(de[mid + 1].nameoff) - nameoff);
/* string comparison without already matched prefix */
int ret = dirnamecmp(name, &dname, &matched);
if (unlikely(!ret))
return de + mid;
else if (ret > 0) {
head = mid + 1;
startprfx = matched;
} else if (unlikely(mid < 1)) /* fix "mid" overflow */
break;
else {
back = mid - 1;
endprfx = matched;
}
}
return ERR_PTR(-ENOENT);
}
static struct page *find_target_block_classic(
struct inode *dir,
struct qstr *name, int *_diff)
{
unsigned startprfx, endprfx;
unsigned head, back;
struct address_space *const mapping = dir->i_mapping;
struct page *candidate = ERR_PTR(-ENOENT);
startprfx = endprfx = 0;
head = 0;
back = inode_datablocks(dir) - 1;
while (head <= back) {
unsigned mid = head + (back - head) / 2;
struct page *page = read_mapping_page(mapping, mid, NULL);
if (IS_ERR(page)) {
exact_out:
if (!IS_ERR(candidate)) /* valid candidate */
put_page(candidate);
return page;
} else {
int diff;
unsigned ndirents, matched;
struct qstr dname;
struct erofs_dirent *de = kmap_atomic(page);
unsigned nameoff = le16_to_cpu(de->nameoff);
ndirents = nameoff / sizeof(*de);
/* corrupted dir (should have one entry at least) */
BUG_ON(!ndirents || nameoff > PAGE_SIZE);
matched = min(startprfx, endprfx);
dname.name = (u8 *)de + nameoff;
dname.len = ndirents == 1 ?
/* since the rest of the last page is 0 */
EROFS_BLKSIZ - nameoff
: le16_to_cpu(de[1].nameoff) - nameoff;
/* string comparison without already matched prefix */
diff = dirnamecmp(name, &dname, &matched);
kunmap_atomic(de);
if (unlikely(!diff)) {
*_diff = 0;
goto exact_out;
} else if (diff > 0) {
head = mid + 1;
startprfx = matched;
if (likely(!IS_ERR(candidate)))
put_page(candidate);
candidate = page;
} else {
put_page(page);
if (unlikely(mid < 1)) /* fix "mid" overflow */
break;
back = mid - 1;
endprfx = matched;
}
}
}
*_diff = 1;
return candidate;
}
int erofs_namei(struct inode *dir,
struct qstr *name,
erofs_nid_t *nid, unsigned *d_type)
{
int diff;
struct page *page;
u8 *data;
struct erofs_dirent *de;
if (unlikely(!dir->i_size))
return -ENOENT;
diff = 1;
page = find_target_block_classic(dir, name, &diff);
if (unlikely(IS_ERR(page)))
return PTR_ERR(page);
data = kmap_atomic(page);
/* the target page has been mapped */
de = likely(diff) ?
/* since the rest of the last page is 0 */
find_target_dirent(name, data, EROFS_BLKSIZ) :
(struct erofs_dirent *)data;
if (likely(!IS_ERR(de))) {
*nid = le64_to_cpu(de->nid);
*d_type = de->file_type;
}
kunmap_atomic(data);
put_page(page);
return IS_ERR(de) ? PTR_ERR(de) : 0;
}
/* NOTE: i_mutex is already held by vfs */
static struct dentry *erofs_lookup(struct inode *dir,
struct dentry *dentry, unsigned int flags)
{
int err;
erofs_nid_t nid;
unsigned d_type;
struct inode *inode;
DBG_BUGON(!d_really_is_negative(dentry));
/* dentry must be unhashed in lookup, no need to worry about */
DBG_BUGON(!d_unhashed(dentry));
/* file name exceeds fs limit */
if (unlikely(dentry->d_name.len > EROFS_NAME_LEN))
return ERR_PTR(-ENAMETOOLONG);
/* false uninitialized warnings on gcc 4.8.x */
err = erofs_namei(dir, &dentry->d_name, &nid, &d_type);
if (err == -ENOENT) {
/* negative dentry */
inode = NULL;
goto negative_out;
} else if (unlikely(err))
return ERR_PTR(err);
debugln("%s, %s (nid %llu) found, d_type %u", __func__,
dentry->d_name.name, nid, d_type);
inode = erofs_iget(dir->i_sb, nid, d_type == EROFS_FT_DIR);
if (IS_ERR(inode))
return ERR_CAST(inode);
negative_out:
return d_splice_alias(inode, dentry);
}
const struct inode_operations erofs_dir_iops = {
.lookup = erofs_lookup,
};
const struct inode_operations erofs_dir_xattr_iops = {
.lookup = erofs_lookup,
};
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment