1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2017-2018 HUAWEI, Inc. 4 * https://www.huawei.com/ 5 * Created by Gao Xiang <gaoxiang25@huawei.com> 6 */ 7 #include "xattr.h" 8 9 #include <trace/events/erofs.h> 10 11 struct erofs_qstr { 12 const unsigned char *name; 13 const unsigned char *end; 14 }; 15 16 /* based on the end of qn is accurate and it must have the trailing '\0' */ 17 static inline int erofs_dirnamecmp(const struct erofs_qstr *qn, 18 const struct erofs_qstr *qd, 19 unsigned int *matched) 20 { 21 unsigned int i = *matched; 22 23 /* 24 * on-disk error, let's only BUG_ON in the debugging mode. 25 * otherwise, it will return 1 to just skip the invalid name 26 * and go on (in consideration of the lookup performance). 27 */ 28 DBG_BUGON(qd->name > qd->end); 29 30 /* qd could not have trailing '\0' */ 31 /* However it is absolutely safe if < qd->end */ 32 while (qd->name + i < qd->end && qd->name[i] != '\0') { 33 if (qn->name[i] != qd->name[i]) { 34 *matched = i; 35 return qn->name[i] > qd->name[i] ? 1 : -1; 36 } 37 ++i; 38 } 39 *matched = i; 40 /* See comments in __d_alloc on the terminating NUL character */ 41 return qn->name[i] == '\0' ? 0 : 1; 42 } 43 44 #define nameoff_from_disk(off, sz) (le16_to_cpu(off) & ((sz) - 1)) 45 46 static struct erofs_dirent *find_target_dirent(struct erofs_qstr *name, 47 u8 *data, 48 unsigned int dirblksize, 49 const int ndirents) 50 { 51 int head, back; 52 unsigned int startprfx, endprfx; 53 struct erofs_dirent *const de = (struct erofs_dirent *)data; 54 55 /* since the 1st dirent has been evaluated previously */ 56 head = 1; 57 back = ndirents - 1; 58 startprfx = endprfx = 0; 59 60 while (head <= back) { 61 const int mid = head + (back - head) / 2; 62 const int nameoff = nameoff_from_disk(de[mid].nameoff, 63 dirblksize); 64 unsigned int matched = min(startprfx, endprfx); 65 struct erofs_qstr dname = { 66 .name = data + nameoff, 67 .end = mid >= ndirents - 1 ? 68 data + dirblksize : 69 data + nameoff_from_disk(de[mid + 1].nameoff, 70 dirblksize) 71 }; 72 73 /* string comparison without already matched prefix */ 74 int ret = erofs_dirnamecmp(name, &dname, &matched); 75 76 if (!ret) { 77 return de + mid; 78 } else if (ret > 0) { 79 head = mid + 1; 80 startprfx = matched; 81 } else { 82 back = mid - 1; 83 endprfx = matched; 84 } 85 } 86 87 return ERR_PTR(-ENOENT); 88 } 89 90 static struct page *find_target_block_classic(struct inode *dir, 91 struct erofs_qstr *name, 92 int *_ndirents) 93 { 94 unsigned int startprfx, endprfx; 95 int head, back; 96 struct address_space *const mapping = dir->i_mapping; 97 struct page *candidate = ERR_PTR(-ENOENT); 98 99 startprfx = endprfx = 0; 100 head = 0; 101 back = erofs_inode_datablocks(dir) - 1; 102 103 while (head <= back) { 104 const int mid = head + (back - head) / 2; 105 struct page *page = read_mapping_page(mapping, mid, NULL); 106 107 if (!IS_ERR(page)) { 108 struct erofs_dirent *de = kmap_atomic(page); 109 const int nameoff = nameoff_from_disk(de->nameoff, 110 EROFS_BLKSIZ); 111 const int ndirents = nameoff / sizeof(*de); 112 int diff; 113 unsigned int matched; 114 struct erofs_qstr dname; 115 116 if (!ndirents) { 117 kunmap_atomic(de); 118 put_page(page); 119 erofs_err(dir->i_sb, 120 "corrupted dir block %d @ nid %llu", 121 mid, EROFS_I(dir)->nid); 122 DBG_BUGON(1); 123 page = ERR_PTR(-EFSCORRUPTED); 124 goto out; 125 } 126 127 matched = min(startprfx, endprfx); 128 129 dname.name = (u8 *)de + nameoff; 130 if (ndirents == 1) 131 dname.end = (u8 *)de + EROFS_BLKSIZ; 132 else 133 dname.end = (u8 *)de + 134 nameoff_from_disk(de[1].nameoff, 135 EROFS_BLKSIZ); 136 137 /* string comparison without already matched prefix */ 138 diff = erofs_dirnamecmp(name, &dname, &matched); 139 kunmap_atomic(de); 140 141 if (!diff) { 142 *_ndirents = 0; 143 goto out; 144 } else if (diff > 0) { 145 head = mid + 1; 146 startprfx = matched; 147 148 if (!IS_ERR(candidate)) 149 put_page(candidate); 150 candidate = page; 151 *_ndirents = ndirents; 152 } else { 153 put_page(page); 154 155 back = mid - 1; 156 endprfx = matched; 157 } 158 continue; 159 } 160 out: /* free if the candidate is valid */ 161 if (!IS_ERR(candidate)) 162 put_page(candidate); 163 return page; 164 } 165 return candidate; 166 } 167 168 int erofs_namei(struct inode *dir, 169 struct qstr *name, 170 erofs_nid_t *nid, unsigned int *d_type) 171 { 172 int ndirents; 173 struct page *page; 174 void *data; 175 struct erofs_dirent *de; 176 struct erofs_qstr qn; 177 178 if (!dir->i_size) 179 return -ENOENT; 180 181 qn.name = name->name; 182 qn.end = name->name + name->len; 183 184 ndirents = 0; 185 page = find_target_block_classic(dir, &qn, &ndirents); 186 187 if (IS_ERR(page)) 188 return PTR_ERR(page); 189 190 data = kmap_atomic(page); 191 /* the target page has been mapped */ 192 if (ndirents) 193 de = find_target_dirent(&qn, data, EROFS_BLKSIZ, ndirents); 194 else 195 de = (struct erofs_dirent *)data; 196 197 if (!IS_ERR(de)) { 198 *nid = le64_to_cpu(de->nid); 199 *d_type = de->file_type; 200 } 201 202 kunmap_atomic(data); 203 put_page(page); 204 205 return PTR_ERR_OR_ZERO(de); 206 } 207 208 /* NOTE: i_mutex is already held by vfs */ 209 static struct dentry *erofs_lookup(struct inode *dir, 210 struct dentry *dentry, 211 unsigned int flags) 212 { 213 int err; 214 erofs_nid_t nid; 215 unsigned int d_type; 216 struct inode *inode; 217 218 DBG_BUGON(!d_really_is_negative(dentry)); 219 /* dentry must be unhashed in lookup, no need to worry about */ 220 DBG_BUGON(!d_unhashed(dentry)); 221 222 trace_erofs_lookup(dir, dentry, flags); 223 224 /* file name exceeds fs limit */ 225 if (dentry->d_name.len > EROFS_NAME_LEN) 226 return ERR_PTR(-ENAMETOOLONG); 227 228 /* false uninitialized warnings on gcc 4.8.x */ 229 err = erofs_namei(dir, &dentry->d_name, &nid, &d_type); 230 231 if (err == -ENOENT) { 232 /* negative dentry */ 233 inode = NULL; 234 } else if (err) { 235 inode = ERR_PTR(err); 236 } else { 237 erofs_dbg("%s, %pd (nid %llu) found, d_type %u", __func__, 238 dentry, nid, d_type); 239 inode = erofs_iget(dir->i_sb, nid, d_type == FT_DIR); 240 } 241 return d_splice_alias(inode, dentry); 242 } 243 244 const struct inode_operations erofs_dir_iops = { 245 .lookup = erofs_lookup, 246 .getattr = erofs_getattr, 247 .listxattr = erofs_listxattr, 248 .get_acl = erofs_get_acl, 249 }; 250 251