1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017-2018 HUAWEI, Inc.
* https://www.huawei.com/
* Copyright (C) 2022, Alibaba Cloud
*/
#include "xattr.h"
#include <trace/events/erofs.h>
struct erofs_qstr {
const unsigned char *name;
const unsigned char *end;
};
/* based on the end of qn is accurate and it must have the trailing '\0' */
static inline int erofs_dirnamecmp(const struct erofs_qstr *qn,
const struct erofs_qstr *qd,
unsigned int *matched)
{
unsigned int i = *matched;
/*
* on-disk error, let's only BUG_ON in the debugging mode.
* otherwise, it will return 1 to just skip the invalid name
* and go on (in consideration of the lookup performance).
*/
DBG_BUGON(qd->name > qd->end);
/* qd could not have trailing '\0' */
/* However it is absolutely safe if < qd->end */
while (qd->name + i < qd->end && qd->name[i] != '\0') {
if (qn->name[i] != qd->name[i]) {
*matched = i;
return qn->name[i] > qd->name[i] ? 1 : -1;
}
++i;
}
*matched = i;
/* See comments in __d_alloc on the terminating NUL character */
return qn->name[i] == '\0' ? 0 : 1;
}
#define nameoff_from_disk(off, sz) (le16_to_cpu(off) & ((sz) - 1))
static struct erofs_dirent *find_target_dirent(struct erofs_qstr *name,
u8 *data,
unsigned int dirblksize,
const int ndirents)
{
int head, back;
unsigned int startprfx, endprfx;
struct erofs_dirent *const de = (struct erofs_dirent *)data;
/* since the 1st dirent has been evaluated previously */
head = 1;
back = ndirents - 1;
startprfx = endprfx = 0;
while (head <= back) {
const int mid = head + (back - head) / 2;
const int nameoff = nameoff_from_disk(de[mid].nameoff,
dirblksize);
unsigned int matched = min(startprfx, endprfx);
struct erofs_qstr dname = {
.name = data + nameoff,
.end = mid >= ndirents - 1 ?
data + dirblksize :
data + nameoff_from_disk(de[mid + 1].nameoff,
dirblksize)
};
/* string comparison without already matched prefix */
int ret = erofs_dirnamecmp(name, &dname, &matched);
if (!ret) {
return de + mid;
} else if (ret > 0) {
head = mid + 1;
startprfx = matched;
} else {
back = mid - 1;
endprfx = matched;
}
}
return ERR_PTR(-ENOENT);
}
static void *erofs_find_target_block(struct erofs_buf *target,
struct inode *dir, struct erofs_qstr *name, int *_ndirents)
{
unsigned int bsz = i_blocksize(dir);
int head = 0, back = erofs_iblks(dir) - 1;
unsigned int startprfx = 0, endprfx = 0;
void *candidate = ERR_PTR(-ENOENT);
while (head <= back) {
const int mid = head + (back - head) / 2;
struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
struct erofs_dirent *de;
buf.inode = dir;
de = erofs_bread(&buf, mid, EROFS_KMAP);
if (!IS_ERR(de)) {
const int nameoff = nameoff_from_disk(de->nameoff, bsz);
const int ndirents = nameoff / sizeof(*de);
int diff;
unsigned int matched;
struct erofs_qstr dname;
if (!ndirents) {
erofs_put_metabuf(&buf);
erofs_err(dir->i_sb,
"corrupted dir block %d @ nid %llu",
mid, EROFS_I(dir)->nid);
DBG_BUGON(1);
de = ERR_PTR(-EFSCORRUPTED);
goto out;
}
matched = min(startprfx, endprfx);
dname.name = (u8 *)de + nameoff;
if (ndirents == 1)
dname.end = (u8 *)de + bsz;
else
dname.end = (u8 *)de +
nameoff_from_disk(de[1].nameoff, bsz);
/* string comparison without already matched prefix */
diff = erofs_dirnamecmp(name, &dname, &matched);
if (diff < 0) {
erofs_put_metabuf(&buf);
back = mid - 1;
endprfx = matched;
continue;
}
if (!IS_ERR(candidate))
erofs_put_metabuf(target);
*target = buf;
if (!diff) {
*_ndirents = 0;
return de;
}
head = mid + 1;
startprfx = matched;
candidate = de;
*_ndirents = ndirents;
continue;
}
out: /* free if the candidate is valid */
if (!IS_ERR(candidate))
erofs_put_metabuf(target);
return de;
}
return candidate;
}
int erofs_namei(struct inode *dir, const struct qstr *name, erofs_nid_t *nid,
unsigned int *d_type)
{
int ndirents;
struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
struct erofs_dirent *de;
struct erofs_qstr qn;
if (!dir->i_size)
return -ENOENT;
qn.name = name->name;
qn.end = name->name + name->len;
buf.inode = dir;
ndirents = 0;
de = erofs_find_target_block(&buf, dir, &qn, &ndirents);
if (IS_ERR(de))
return PTR_ERR(de);
if (ndirents)
de = find_target_dirent(&qn, (u8 *)de, i_blocksize(dir),
ndirents);
if (!IS_ERR(de)) {
*nid = le64_to_cpu(de->nid);
*d_type = de->file_type;
}
erofs_put_metabuf(&buf);
return PTR_ERR_OR_ZERO(de);
}
static struct dentry *erofs_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
int err;
erofs_nid_t nid;
unsigned int d_type;
struct inode *inode;
trace_erofs_lookup(dir, dentry, flags);
if (dentry->d_name.len > EROFS_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);
err = erofs_namei(dir, &dentry->d_name, &nid, &d_type);
if (err == -ENOENT)
/* negative dentry */
inode = NULL;
else if (err)
inode = ERR_PTR(err);
else
inode = erofs_iget(dir->i_sb, nid);
return d_splice_alias(inode, dentry);
}
const struct inode_operations erofs_dir_iops = {
.lookup = erofs_lookup,
.getattr = erofs_getattr,
.listxattr = erofs_listxattr,
.get_inode_acl = erofs_get_acl,
.fiemap = erofs_fiemap,
};
|
