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