1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/fs.h>
4 #include <linux/types.h>
5 #include "ctree.h"
6 #include "disk-io.h"
7 #include "btrfs_inode.h"
8 #include "export.h"
9 #include "accessors.h"
10 #include "super.h"
11
12 #define BTRFS_FID_SIZE_NON_CONNECTABLE (offsetof(struct btrfs_fid, \
13 parent_objectid) / 4)
14 #define BTRFS_FID_SIZE_CONNECTABLE (offsetof(struct btrfs_fid, \
15 parent_root_objectid) / 4)
16 #define BTRFS_FID_SIZE_CONNECTABLE_ROOT (sizeof(struct btrfs_fid) / 4)
17
18 static int btrfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
19 struct inode *parent)
20 {
21 struct btrfs_fid *fid = (struct btrfs_fid *)fh;
22 int len = *max_len;
23 int type;
24
25 if (parent && (len < BTRFS_FID_SIZE_CONNECTABLE)) {
26 *max_len = BTRFS_FID_SIZE_CONNECTABLE;
27 return FILEID_INVALID;
28 } else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
29 *max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;
30 return FILEID_INVALID;
31 }
32
33 len = BTRFS_FID_SIZE_NON_CONNECTABLE;
34 type = FILEID_BTRFS_WITHOUT_PARENT;
35
36 fid->objectid = btrfs_ino(BTRFS_I(inode));
37 fid->root_objectid = btrfs_root_id(BTRFS_I(inode)->root);
38 fid->gen = inode->i_generation;
39
40 if (parent) {
41 u64 parent_root_id;
42
43 fid->parent_objectid = btrfs_ino(BTRFS_I(parent));
44 fid->parent_gen = parent->i_generation;
45 parent_root_id = btrfs_root_id(BTRFS_I(parent)->root);
46
47 if (parent_root_id != fid->root_objectid) {
48 fid->parent_root_objectid = parent_root_id;
49 len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
50 type = FILEID_BTRFS_WITH_PARENT_ROOT;
51 } else {
52 len = BTRFS_FID_SIZE_CONNECTABLE;
53 type = FILEID_BTRFS_WITH_PARENT;
54 }
55 }
56
57 *max_len = len;
58 return type;
59 }
60
61 /*
62 * Read dentry of inode with @objectid from filesystem root @root_objectid.
63 *
64 * @sb: the filesystem super block
65 * @objectid: inode objectid
66 * @root_objectid: object id of the subvolume root where to look up the inode
67 * @generation: optional, if not zero, verify that the found inode
68 * generation matches
69 *
70 * Return dentry alias for the inode, otherwise an error. In case the
71 * generation does not match return ESTALE.
72 */
73 struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
74 u64 root_objectid, u64 generation)
75 {
76 struct btrfs_fs_info *fs_info = btrfs_sb(sb);
77 struct btrfs_root *root;
78 struct inode *inode;
79
80 if (objectid < BTRFS_FIRST_FREE_OBJECTID)
81 return ERR_PTR(-ESTALE);
82
83 root = btrfs_get_fs_root(fs_info, root_objectid, true);
84 if (IS_ERR(root))
85 return ERR_CAST(root);
86
87 inode = btrfs_iget(objectid, root);
88 btrfs_put_root(root);
89 if (IS_ERR(inode))
90 return ERR_CAST(inode);
91
92 if (generation != 0 && generation != inode->i_generation) {
93 iput(inode);
94 return ERR_PTR(-ESTALE);
95 }
96
97 return d_obtain_alias(inode);
98 }
99
100 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
101 int fh_len, int fh_type)
102 {
103 struct btrfs_fid *fid = (struct btrfs_fid *) fh;
104 u64 objectid, root_objectid;
105 u32 generation;
106
107 if (fh_type == FILEID_BTRFS_WITH_PARENT) {
108 if (fh_len < BTRFS_FID_SIZE_CONNECTABLE)
109 return NULL;
110 root_objectid = fid->root_objectid;
111 } else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
112 if (fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
113 return NULL;
114 root_objectid = fid->parent_root_objectid;
115 } else
116 return NULL;
117
118 objectid = fid->parent_objectid;
119 generation = fid->parent_gen;
120
121 return btrfs_get_dentry(sb, objectid, root_objectid, generation);
122 }
123
124 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
125 int fh_len, int fh_type)
126 {
127 struct btrfs_fid *fid = (struct btrfs_fid *) fh;
128 u64 objectid, root_objectid;
129 u32 generation;
130
131 if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
132 fh_len < BTRFS_FID_SIZE_CONNECTABLE) &&
133 (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
134 fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
135 (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
136 fh_len < BTRFS_FID_SIZE_NON_CONNECTABLE))
137 return NULL;
138
139 objectid = fid->objectid;
140 root_objectid = fid->root_objectid;
141 generation = fid->gen;
142
143 return btrfs_get_dentry(sb, objectid, root_objectid, generation);
144 }
145
146 struct dentry *btrfs_get_parent(struct dentry *child)
147 {
148 struct inode *dir = d_inode(child);
149 struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
150 struct btrfs_root *root = BTRFS_I(dir)->root;
151 struct btrfs_path *path;
152 struct extent_buffer *leaf;
153 struct btrfs_root_ref *ref;
154 struct btrfs_key key;
155 struct btrfs_key found_key;
156 int ret;
157
158 path = btrfs_alloc_path();
159 if (!path)
160 return ERR_PTR(-ENOMEM);
161
162 if (btrfs_ino(BTRFS_I(dir)) == BTRFS_FIRST_FREE_OBJECTID) {
163 key.objectid = btrfs_root_id(root);
164 key.type = BTRFS_ROOT_BACKREF_KEY;
165 key.offset = (u64)-1;
166 root = fs_info->tree_root;
167 } else {
168 key.objectid = btrfs_ino(BTRFS_I(dir));
169 key.type = BTRFS_INODE_REF_KEY;
170 key.offset = (u64)-1;
171 }
172
173 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
174 if (ret < 0)
175 goto fail;
176 if (ret == 0) {
177 /*
178 * Key with offset of -1 found, there would have to exist an
179 * inode with such number or a root with such id.
180 */
181 ret = -EUCLEAN;
182 goto fail;
183 }
184
185 if (path->slots[0] == 0) {
186 ret = -ENOENT;
187 goto fail;
188 }
189
190 path->slots[0]--;
191 leaf = path->nodes[0];
192
193 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
194 if (found_key.objectid != key.objectid || found_key.type != key.type) {
195 ret = -ENOENT;
196 goto fail;
197 }
198
199 if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
200 ref = btrfs_item_ptr(leaf, path->slots[0],
201 struct btrfs_root_ref);
202 key.objectid = btrfs_root_ref_dirid(leaf, ref);
203 } else {
204 key.objectid = found_key.offset;
205 }
206 btrfs_free_path(path);
207
208 if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
209 return btrfs_get_dentry(fs_info->sb, key.objectid,
210 found_key.offset, 0);
211 }
212
213 return d_obtain_alias(btrfs_iget(key.objectid, root));
214 fail:
215 btrfs_free_path(path);
216 return ERR_PTR(ret);
217 }
218
219 static int btrfs_get_name(struct dentry *parent, char *name,
220 struct dentry *child)
221 {
222 struct inode *inode = d_inode(child);
223 struct inode *dir = d_inode(parent);
224 struct btrfs_fs_info *fs_info = inode_to_fs_info(inode);
225 struct btrfs_path *path;
226 struct btrfs_root *root = BTRFS_I(dir)->root;
227 struct btrfs_inode_ref *iref;
228 struct btrfs_root_ref *rref;
229 struct extent_buffer *leaf;
230 unsigned long name_ptr;
231 struct btrfs_key key;
232 int name_len;
233 int ret;
234 u64 ino;
235
236 if (!S_ISDIR(dir->i_mode))
237 return -EINVAL;
238
239 ino = btrfs_ino(BTRFS_I(inode));
240
241 path = btrfs_alloc_path();
242 if (!path)
243 return -ENOMEM;
244
245 if (ino == BTRFS_FIRST_FREE_OBJECTID) {
246 key.objectid = btrfs_root_id(BTRFS_I(inode)->root);
247 key.type = BTRFS_ROOT_BACKREF_KEY;
248 key.offset = (u64)-1;
249 root = fs_info->tree_root;
250 } else {
251 key.objectid = ino;
252 key.offset = btrfs_ino(BTRFS_I(dir));
253 key.type = BTRFS_INODE_REF_KEY;
254 }
255
256 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
257 if (ret < 0) {
258 btrfs_free_path(path);
259 return ret;
260 } else if (ret > 0) {
261 if (ino == BTRFS_FIRST_FREE_OBJECTID) {
262 path->slots[0]--;
263 } else {
264 btrfs_free_path(path);
265 return -ENOENT;
266 }
267 }
268 leaf = path->nodes[0];
269
270 if (ino == BTRFS_FIRST_FREE_OBJECTID) {
271 rref = btrfs_item_ptr(leaf, path->slots[0],
272 struct btrfs_root_ref);
273 name_ptr = (unsigned long)(rref + 1);
274 name_len = btrfs_root_ref_name_len(leaf, rref);
275 } else {
276 iref = btrfs_item_ptr(leaf, path->slots[0],
277 struct btrfs_inode_ref);
278 name_ptr = (unsigned long)(iref + 1);
279 name_len = btrfs_inode_ref_name_len(leaf, iref);
280 }
281
282 read_extent_buffer(leaf, name, name_ptr, name_len);
283 btrfs_free_path(path);
284
285 /*
286 * have to add the null termination to make sure that reconnect_path
287 * gets the right len for strlen
288 */
289 name[name_len] = '\0';
290
291 return 0;
292 }
293
294 const struct export_operations btrfs_export_ops = {
295 .encode_fh = btrfs_encode_fh,
296 .fh_to_dentry = btrfs_fh_to_dentry,
297 .fh_to_parent = btrfs_fh_to_parent,
298 .get_parent = btrfs_get_parent,
299 .get_name = btrfs_get_name,
300 };
301
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