forked from Minki/linux
staging: erofs: add namei functions
This commit adds functions that transfer names to inodes. Signed-off-by: Miao Xie <miaoxie@huawei.com> Signed-off-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gao Xiang
Greg Kroah-Hartman
parent
3aa8ec716e
commit
d72d1ce601
243
drivers/staging/erofs/namei.c
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243
drivers/staging/erofs/namei.c
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@ -0,0 +1,243 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/drivers/staging/erofs/namei.c
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*
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* Copyright (C) 2017-2018 HUAWEI, Inc.
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* http://www.huawei.com/
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* Created by Gao Xiang <gaoxiang25@huawei.com>
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file COPYING in the main directory of the Linux
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* distribution for more details.
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*/
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#include "internal.h"
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/* based on the value of qn->len is accurate */
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static inline int dirnamecmp(struct qstr *qn,
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struct qstr *qd, unsigned *matched)
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{
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unsigned i = *matched, len = min(qn->len, qd->len);
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loop:
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if (unlikely(i >= len)) {
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*matched = i;
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if (qn->len < qd->len) {
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/*
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* actually (qn->len == qd->len)
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* when qd->name[i] == '\0'
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*/
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return qd->name[i] == '\0' ? 0 : -1;
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}
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return (qn->len > qd->len);
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}
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if (qn->name[i] != qd->name[i]) {
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*matched = i;
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return qn->name[i] > qd->name[i] ? 1 : -1;
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}
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++i;
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goto loop;
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}
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static struct erofs_dirent *find_target_dirent(
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struct qstr *name,
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u8 *data, int maxsize)
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{
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unsigned ndirents, head, back;
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unsigned startprfx, endprfx;
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struct erofs_dirent *const de = (struct erofs_dirent *)data;
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/* make sure that maxsize is valid */
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BUG_ON(maxsize < sizeof(struct erofs_dirent));
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ndirents = le16_to_cpu(de->nameoff) / sizeof(*de);
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/* corrupted dir (may be unnecessary...) */
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BUG_ON(!ndirents);
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head = 0;
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back = ndirents - 1;
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startprfx = endprfx = 0;
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while (head <= back) {
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unsigned mid = head + (back - head) / 2;
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unsigned nameoff = le16_to_cpu(de[mid].nameoff);
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unsigned matched = min(startprfx, endprfx);
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struct qstr dname = QSTR_INIT(data + nameoff,
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unlikely(mid >= ndirents - 1) ?
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maxsize - nameoff :
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le16_to_cpu(de[mid + 1].nameoff) - nameoff);
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/* string comparison without already matched prefix */
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int ret = dirnamecmp(name, &dname, &matched);
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if (unlikely(!ret))
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return de + mid;
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else if (ret > 0) {
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head = mid + 1;
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startprfx = matched;
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} else if (unlikely(mid < 1)) /* fix "mid" overflow */
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break;
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else {
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back = mid - 1;
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endprfx = matched;
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}
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}
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return ERR_PTR(-ENOENT);
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}
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static struct page *find_target_block_classic(
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struct inode *dir,
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struct qstr *name, int *_diff)
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{
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unsigned startprfx, endprfx;
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unsigned head, back;
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struct address_space *const mapping = dir->i_mapping;
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struct page *candidate = ERR_PTR(-ENOENT);
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startprfx = endprfx = 0;
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head = 0;
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back = inode_datablocks(dir) - 1;
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while (head <= back) {
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unsigned mid = head + (back - head) / 2;
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struct page *page = read_mapping_page(mapping, mid, NULL);
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if (IS_ERR(page)) {
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exact_out:
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if (!IS_ERR(candidate)) /* valid candidate */
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put_page(candidate);
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return page;
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} else {
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int diff;
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unsigned ndirents, matched;
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struct qstr dname;
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struct erofs_dirent *de = kmap_atomic(page);
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unsigned nameoff = le16_to_cpu(de->nameoff);
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ndirents = nameoff / sizeof(*de);
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/* corrupted dir (should have one entry at least) */
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BUG_ON(!ndirents || nameoff > PAGE_SIZE);
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matched = min(startprfx, endprfx);
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dname.name = (u8 *)de + nameoff;
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dname.len = ndirents == 1 ?
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/* since the rest of the last page is 0 */
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EROFS_BLKSIZ - nameoff
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: le16_to_cpu(de[1].nameoff) - nameoff;
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/* string comparison without already matched prefix */
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diff = dirnamecmp(name, &dname, &matched);
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kunmap_atomic(de);
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if (unlikely(!diff)) {
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*_diff = 0;
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goto exact_out;
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} else if (diff > 0) {
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head = mid + 1;
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startprfx = matched;
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if (likely(!IS_ERR(candidate)))
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put_page(candidate);
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candidate = page;
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} else {
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put_page(page);
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if (unlikely(mid < 1)) /* fix "mid" overflow */
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break;
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back = mid - 1;
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endprfx = matched;
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}
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}
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}
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*_diff = 1;
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return candidate;
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}
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int erofs_namei(struct inode *dir,
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struct qstr *name,
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erofs_nid_t *nid, unsigned *d_type)
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{
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int diff;
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struct page *page;
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u8 *data;
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struct erofs_dirent *de;
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if (unlikely(!dir->i_size))
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return -ENOENT;
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diff = 1;
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page = find_target_block_classic(dir, name, &diff);
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if (unlikely(IS_ERR(page)))
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return PTR_ERR(page);
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data = kmap_atomic(page);
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/* the target page has been mapped */
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de = likely(diff) ?
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/* since the rest of the last page is 0 */
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find_target_dirent(name, data, EROFS_BLKSIZ) :
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(struct erofs_dirent *)data;
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if (likely(!IS_ERR(de))) {
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*nid = le64_to_cpu(de->nid);
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*d_type = de->file_type;
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}
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kunmap_atomic(data);
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put_page(page);
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return IS_ERR(de) ? PTR_ERR(de) : 0;
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}
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/* NOTE: i_mutex is already held by vfs */
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static struct dentry *erofs_lookup(struct inode *dir,
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struct dentry *dentry, unsigned int flags)
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{
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int err;
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erofs_nid_t nid;
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unsigned d_type;
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struct inode *inode;
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DBG_BUGON(!d_really_is_negative(dentry));
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/* dentry must be unhashed in lookup, no need to worry about */
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DBG_BUGON(!d_unhashed(dentry));
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/* file name exceeds fs limit */
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if (unlikely(dentry->d_name.len > EROFS_NAME_LEN))
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return ERR_PTR(-ENAMETOOLONG);
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/* false uninitialized warnings on gcc 4.8.x */
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err = erofs_namei(dir, &dentry->d_name, &nid, &d_type);
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if (err == -ENOENT) {
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/* negative dentry */
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inode = NULL;
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goto negative_out;
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} else if (unlikely(err))
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return ERR_PTR(err);
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debugln("%s, %s (nid %llu) found, d_type %u", __func__,
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dentry->d_name.name, nid, d_type);
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inode = erofs_iget(dir->i_sb, nid, d_type == EROFS_FT_DIR);
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if (IS_ERR(inode))
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return ERR_CAST(inode);
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negative_out:
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return d_splice_alias(inode, dentry);
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}
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const struct inode_operations erofs_dir_iops = {
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.lookup = erofs_lookup,
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};
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const struct inode_operations erofs_dir_xattr_iops = {
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.lookup = erofs_lookup,
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};
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