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' */ 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 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 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 } 166 167 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 */ 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 }; 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