1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2017-2018 HUAWEI, Inc.
4 * https://www.huawei.com/
5 */
6 #include "xattr.h"
7
8 #include <trace/events/erofs.h>
9
10 struct erofs_qstr {
11 const unsigned char *name;
12 const unsigned char *end;
13 };
14
15 /* based on the end of qn is accurate and it must have the trailing '\0' */
erofs_dirnamecmp(const struct erofs_qstr * qn,const struct erofs_qstr * qd,unsigned int * matched)16 static inline int erofs_dirnamecmp(const struct erofs_qstr *qn,
17 const struct erofs_qstr *qd,
18 unsigned int *matched)
19 {
20 unsigned int i = *matched;
21
22 /*
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).
26 */
27 DBG_BUGON(qd->name > qd->end);
28
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]) {
33 *matched = i;
34 return qn->name[i] > qd->name[i] ? 1 : -1;
35 }
36 ++i;
37 }
38 *matched = i;
39 /* See comments in __d_alloc on the terminating NUL character */
40 return qn->name[i] == '\0' ? 0 : 1;
41 }
42
43 #define nameoff_from_disk(off, sz) (le16_to_cpu(off) & ((sz) - 1))
44
find_target_dirent(struct erofs_qstr * name,u8 * data,unsigned int dirblksize,const int ndirents)45 static struct erofs_dirent *find_target_dirent(struct erofs_qstr *name,
46 u8 *data,
47 unsigned int dirblksize,
48 const int ndirents)
49 {
50 int head, back;
51 unsigned int startprfx, endprfx;
52 struct erofs_dirent *const de = (struct erofs_dirent *)data;
53
54 /* since the 1st dirent has been evaluated previously */
55 head = 1;
56 back = ndirents - 1;
57 startprfx = endprfx = 0;
58
59 while (head <= back) {
60 const int mid = head + (back - head) / 2;
61 const int nameoff = nameoff_from_disk(de[mid].nameoff,
62 dirblksize);
63 unsigned int matched = min(startprfx, endprfx);
64 struct erofs_qstr dname = {
65 .name = data + nameoff,
66 .end = mid >= ndirents - 1 ?
67 data + dirblksize :
68 data + nameoff_from_disk(de[mid + 1].nameoff,
69 dirblksize)
70 };
71
72 /* string comparison without already matched prefix */
73 int ret = erofs_dirnamecmp(name, &dname, &matched);
74
75 if (!ret) {
76 return de + mid;
77 } else if (ret > 0) {
78 head = mid + 1;
79 startprfx = matched;
80 } else {
81 back = mid - 1;
82 endprfx = matched;
83 }
84 }
85
86 return ERR_PTR(-ENOENT);
87 }
88
find_target_block_classic(struct inode * dir,struct erofs_qstr * name,int * _ndirents)89 static struct page *find_target_block_classic(struct inode *dir,
90 struct erofs_qstr *name,
91 int *_ndirents)
92 {
93 unsigned int startprfx, endprfx;
94 int head, back;
95 struct address_space *const mapping = dir->i_mapping;
96 struct page *candidate = ERR_PTR(-ENOENT);
97
98 startprfx = endprfx = 0;
99 head = 0;
100 back = erofs_inode_datablocks(dir) - 1;
101
102 while (head <= back) {
103 const int mid = head + (back - head) / 2;
104 struct page *page = read_mapping_page(mapping, mid, NULL);
105
106 if (!IS_ERR(page)) {
107 struct erofs_dirent *de = kmap_atomic(page);
108 const int nameoff = nameoff_from_disk(de->nameoff,
109 EROFS_BLKSIZ);
110 const int ndirents = nameoff / sizeof(*de);
111 int diff;
112 unsigned int matched;
113 struct erofs_qstr dname;
114
115 if (!ndirents) {
116 kunmap_atomic(de);
117 put_page(page);
118 erofs_err(dir->i_sb,
119 "corrupted dir block %d @ nid %llu",
120 mid, EROFS_I(dir)->nid);
121 DBG_BUGON(1);
122 page = ERR_PTR(-EFSCORRUPTED);
123 goto out;
124 }
125
126 matched = min(startprfx, endprfx);
127
128 dname.name = (u8 *)de + nameoff;
129 if (ndirents == 1)
130 dname.end = (u8 *)de + EROFS_BLKSIZ;
131 else
132 dname.end = (u8 *)de +
133 nameoff_from_disk(de[1].nameoff,
134 EROFS_BLKSIZ);
135
136 /* string comparison without already matched prefix */
137 diff = erofs_dirnamecmp(name, &dname, &matched);
138 kunmap_atomic(de);
139
140 if (!diff) {
141 *_ndirents = 0;
142 goto out;
143 } else if (diff > 0) {
144 head = mid + 1;
145 startprfx = matched;
146
147 if (!IS_ERR(candidate))
148 put_page(candidate);
149 candidate = page;
150 *_ndirents = ndirents;
151 } else {
152 put_page(page);
153
154 back = mid - 1;
155 endprfx = matched;
156 }
157 continue;
158 }
159 out: /* free if the candidate is valid */
160 if (!IS_ERR(candidate))
161 put_page(candidate);
162 return page;
163 }
164 return candidate;
165 }
166
erofs_namei(struct inode * dir,struct qstr * name,erofs_nid_t * nid,unsigned int * d_type)167 int erofs_namei(struct inode *dir,
168 struct qstr *name,
169 erofs_nid_t *nid, unsigned int *d_type)
170 {
171 int ndirents;
172 struct page *page;
173 void *data;
174 struct erofs_dirent *de;
175 struct erofs_qstr qn;
176
177 if (!dir->i_size)
178 return -ENOENT;
179
180 qn.name = name->name;
181 qn.end = name->name + name->len;
182
183 ndirents = 0;
184 page = find_target_block_classic(dir, &qn, &ndirents);
185
186 if (IS_ERR(page))
187 return PTR_ERR(page);
188
189 data = kmap_atomic(page);
190 /* the target page has been mapped */
191 if (ndirents)
192 de = find_target_dirent(&qn, data, EROFS_BLKSIZ, ndirents);
193 else
194 de = (struct erofs_dirent *)data;
195
196 if (!IS_ERR(de)) {
197 *nid = le64_to_cpu(de->nid);
198 *d_type = de->file_type;
199 }
200
201 kunmap_atomic(data);
202 put_page(page);
203
204 return PTR_ERR_OR_ZERO(de);
205 }
206
207 /* NOTE: i_mutex is already held by vfs */
erofs_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)208 static struct dentry *erofs_lookup(struct inode *dir,
209 struct dentry *dentry,
210 unsigned int flags)
211 {
212 int err;
213 erofs_nid_t nid;
214 unsigned int d_type;
215 struct inode *inode;
216
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));
220
221 trace_erofs_lookup(dir, dentry, flags);
222
223 /* file name exceeds fs limit */
224 if (dentry->d_name.len > EROFS_NAME_LEN)
225 return ERR_PTR(-ENAMETOOLONG);
226
227 /* false uninitialized warnings on gcc 4.8.x */
228 err = erofs_namei(dir, &dentry->d_name, &nid, &d_type);
229
230 if (err == -ENOENT) {
231 /* negative dentry */
232 inode = NULL;
233 } else if (err) {
234 inode = ERR_PTR(err);
235 } else {
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);
239 }
240 return d_splice_alias(inode, dentry);
241 }
242
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,
249 };
250