1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright (C) 2017-2018 HUAWEI, Inc.
4 * https://www.huawei.com/
8 #include <trace/events/erofs.h>
11 const unsigned char *name;
12 const unsigned char *end;
15 /* based on the end of qn is accurate and it must have the trailing '\0' */
16 static inline int erofs_dirnamecmp(const struct erofs_qstr *qn,
17 const struct erofs_qstr *qd,
18 unsigned int *matched)
20 unsigned int i = *matched;
23 * on-disk error, let's only BUG_ON in the debugging mode.
24 * otherwise, it will return 1 to just skip the invalid name
25 * and go on (in consideration of the lookup performance).
27 DBG_BUGON(qd->name > qd->end);
29 /* qd could not have trailing '\0' */
30 /* However it is absolutely safe if < qd->end */
31 while (qd->name + i < qd->end && qd->name[i] != '\0') {
32 if (qn->name[i] != qd->name[i]) {
34 return qn->name[i] > qd->name[i] ? 1 : -1;
39 /* See comments in __d_alloc on the terminating NUL character */
40 return qn->name[i] == '\0' ? 0 : 1;
43 #define nameoff_from_disk(off, sz) (le16_to_cpu(off) & ((sz) - 1))
45 static struct erofs_dirent *find_target_dirent(struct erofs_qstr *name,
47 unsigned int dirblksize,
51 unsigned int startprfx, endprfx;
52 struct erofs_dirent *const de = (struct erofs_dirent *)data;
54 /* since the 1st dirent has been evaluated previously */
57 startprfx = endprfx = 0;
59 while (head <= back) {
60 const int mid = head + (back - head) / 2;
61 const int nameoff = nameoff_from_disk(de[mid].nameoff,
63 unsigned int matched = min(startprfx, endprfx);
64 struct erofs_qstr dname = {
65 .name = data + nameoff,
66 .end = mid >= ndirents - 1 ?
68 data + nameoff_from_disk(de[mid + 1].nameoff,
72 /* string comparison without already matched prefix */
73 int ret = erofs_dirnamecmp(name, &dname, &matched);
86 return ERR_PTR(-ENOENT);
89 static struct page *find_target_block_classic(struct inode *dir,
90 struct erofs_qstr *name,
93 unsigned int startprfx, endprfx;
95 struct address_space *const mapping = dir->i_mapping;
96 struct page *candidate = ERR_PTR(-ENOENT);
98 startprfx = endprfx = 0;
100 back = erofs_inode_datablocks(dir) - 1;
102 while (head <= back) {
103 const int mid = head + (back - head) / 2;
104 struct page *page = read_mapping_page(mapping, mid, NULL);
107 struct erofs_dirent *de = kmap_atomic(page);
108 const int nameoff = nameoff_from_disk(de->nameoff,
110 const int ndirents = nameoff / sizeof(*de);
112 unsigned int matched;
113 struct erofs_qstr dname;
119 "corrupted dir block %d @ nid %llu",
120 mid, EROFS_I(dir)->nid);
122 page = ERR_PTR(-EFSCORRUPTED);
126 matched = min(startprfx, endprfx);
128 dname.name = (u8 *)de + nameoff;
130 dname.end = (u8 *)de + EROFS_BLKSIZ;
132 dname.end = (u8 *)de +
133 nameoff_from_disk(de[1].nameoff,
136 /* string comparison without already matched prefix */
137 diff = erofs_dirnamecmp(name, &dname, &matched);
143 } else if (diff > 0) {
147 if (!IS_ERR(candidate))
150 *_ndirents = ndirents;
159 out: /* free if the candidate is valid */
160 if (!IS_ERR(candidate))
167 int erofs_namei(struct inode *dir,
169 erofs_nid_t *nid, unsigned int *d_type)
174 struct erofs_dirent *de;
175 struct erofs_qstr qn;
180 qn.name = name->name;
181 qn.end = name->name + name->len;
184 page = find_target_block_classic(dir, &qn, &ndirents);
187 return PTR_ERR(page);
189 data = kmap_atomic(page);
190 /* the target page has been mapped */
192 de = find_target_dirent(&qn, data, EROFS_BLKSIZ, ndirents);
194 de = (struct erofs_dirent *)data;
197 *nid = le64_to_cpu(de->nid);
198 *d_type = de->file_type;
204 return PTR_ERR_OR_ZERO(de);
207 /* NOTE: i_mutex is already held by vfs */
208 static struct dentry *erofs_lookup(struct inode *dir,
209 struct dentry *dentry,
217 DBG_BUGON(!d_really_is_negative(dentry));
218 /* dentry must be unhashed in lookup, no need to worry about */
219 DBG_BUGON(!d_unhashed(dentry));
221 trace_erofs_lookup(dir, dentry, flags);
223 /* file name exceeds fs limit */
224 if (dentry->d_name.len > EROFS_NAME_LEN)
225 return ERR_PTR(-ENAMETOOLONG);
227 /* false uninitialized warnings on gcc 4.8.x */
228 err = erofs_namei(dir, &dentry->d_name, &nid, &d_type);
230 if (err == -ENOENT) {
231 /* negative dentry */
234 inode = ERR_PTR(err);
236 erofs_dbg("%s, %pd (nid %llu) found, d_type %u", __func__,
237 dentry, nid, d_type);
238 inode = erofs_iget(dir->i_sb, nid, d_type == FT_DIR);
240 return d_splice_alias(inode, dentry);
243 const struct inode_operations erofs_dir_iops = {
244 .lookup = erofs_lookup,
245 .getattr = erofs_getattr,
246 .listxattr = erofs_listxattr,
247 .get_acl = erofs_get_acl,
248 .fiemap = erofs_fiemap,