xref: /openbmc/linux/fs/btrfs/export.c (revision 82df5b73)
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 
11 #define BTRFS_FID_SIZE_NON_CONNECTABLE (offsetof(struct btrfs_fid, \
12 						 parent_objectid) / 4)
13 #define BTRFS_FID_SIZE_CONNECTABLE (offsetof(struct btrfs_fid, \
14 					     parent_root_objectid) / 4)
15 #define BTRFS_FID_SIZE_CONNECTABLE_ROOT (sizeof(struct btrfs_fid) / 4)
16 
17 static int btrfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
18 			   struct inode *parent)
19 {
20 	struct btrfs_fid *fid = (struct btrfs_fid *)fh;
21 	int len = *max_len;
22 	int type;
23 
24 	if (parent && (len < BTRFS_FID_SIZE_CONNECTABLE)) {
25 		*max_len = BTRFS_FID_SIZE_CONNECTABLE;
26 		return FILEID_INVALID;
27 	} else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
28 		*max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;
29 		return FILEID_INVALID;
30 	}
31 
32 	len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
33 	type = FILEID_BTRFS_WITHOUT_PARENT;
34 
35 	fid->objectid = btrfs_ino(BTRFS_I(inode));
36 	fid->root_objectid = BTRFS_I(inode)->root->root_key.objectid;
37 	fid->gen = inode->i_generation;
38 
39 	if (parent) {
40 		u64 parent_root_id;
41 
42 		fid->parent_objectid = BTRFS_I(parent)->location.objectid;
43 		fid->parent_gen = parent->i_generation;
44 		parent_root_id = BTRFS_I(parent)->root->root_key.objectid;
45 
46 		if (parent_root_id != fid->root_objectid) {
47 			fid->parent_root_objectid = parent_root_id;
48 			len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
49 			type = FILEID_BTRFS_WITH_PARENT_ROOT;
50 		} else {
51 			len = BTRFS_FID_SIZE_CONNECTABLE;
52 			type = FILEID_BTRFS_WITH_PARENT;
53 		}
54 	}
55 
56 	*max_len = len;
57 	return type;
58 }
59 
60 struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
61 				u64 root_objectid, u32 generation,
62 				int check_generation)
63 {
64 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
65 	struct btrfs_root *root;
66 	struct inode *inode;
67 
68 	if (objectid < BTRFS_FIRST_FREE_OBJECTID)
69 		return ERR_PTR(-ESTALE);
70 
71 	root = btrfs_get_fs_root(fs_info, root_objectid, true);
72 	if (IS_ERR(root))
73 		return ERR_CAST(root);
74 
75 	inode = btrfs_iget(sb, objectid, root);
76 	btrfs_put_root(root);
77 	if (IS_ERR(inode))
78 		return ERR_CAST(inode);
79 
80 	if (check_generation && generation != inode->i_generation) {
81 		iput(inode);
82 		return ERR_PTR(-ESTALE);
83 	}
84 
85 	return d_obtain_alias(inode);
86 }
87 
88 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
89 					 int fh_len, int fh_type)
90 {
91 	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
92 	u64 objectid, root_objectid;
93 	u32 generation;
94 
95 	if (fh_type == FILEID_BTRFS_WITH_PARENT) {
96 		if (fh_len <  BTRFS_FID_SIZE_CONNECTABLE)
97 			return NULL;
98 		root_objectid = fid->root_objectid;
99 	} else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
100 		if (fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
101 			return NULL;
102 		root_objectid = fid->parent_root_objectid;
103 	} else
104 		return NULL;
105 
106 	objectid = fid->parent_objectid;
107 	generation = fid->parent_gen;
108 
109 	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
110 }
111 
112 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
113 					 int fh_len, int fh_type)
114 {
115 	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
116 	u64 objectid, root_objectid;
117 	u32 generation;
118 
119 	if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
120 	     fh_len < BTRFS_FID_SIZE_CONNECTABLE) &&
121 	    (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
122 	     fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
123 	    (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
124 	     fh_len < BTRFS_FID_SIZE_NON_CONNECTABLE))
125 		return NULL;
126 
127 	objectid = fid->objectid;
128 	root_objectid = fid->root_objectid;
129 	generation = fid->gen;
130 
131 	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
132 }
133 
134 struct dentry *btrfs_get_parent(struct dentry *child)
135 {
136 	struct inode *dir = d_inode(child);
137 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
138 	struct btrfs_root *root = BTRFS_I(dir)->root;
139 	struct btrfs_path *path;
140 	struct extent_buffer *leaf;
141 	struct btrfs_root_ref *ref;
142 	struct btrfs_key key;
143 	struct btrfs_key found_key;
144 	int ret;
145 
146 	path = btrfs_alloc_path();
147 	if (!path)
148 		return ERR_PTR(-ENOMEM);
149 
150 	if (btrfs_ino(BTRFS_I(dir)) == BTRFS_FIRST_FREE_OBJECTID) {
151 		key.objectid = root->root_key.objectid;
152 		key.type = BTRFS_ROOT_BACKREF_KEY;
153 		key.offset = (u64)-1;
154 		root = fs_info->tree_root;
155 	} else {
156 		key.objectid = btrfs_ino(BTRFS_I(dir));
157 		key.type = BTRFS_INODE_REF_KEY;
158 		key.offset = (u64)-1;
159 	}
160 
161 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
162 	if (ret < 0)
163 		goto fail;
164 
165 	BUG_ON(ret == 0); /* Key with offset of -1 found */
166 	if (path->slots[0] == 0) {
167 		ret = -ENOENT;
168 		goto fail;
169 	}
170 
171 	path->slots[0]--;
172 	leaf = path->nodes[0];
173 
174 	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
175 	if (found_key.objectid != key.objectid || found_key.type != key.type) {
176 		ret = -ENOENT;
177 		goto fail;
178 	}
179 
180 	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
181 		ref = btrfs_item_ptr(leaf, path->slots[0],
182 				     struct btrfs_root_ref);
183 		key.objectid = btrfs_root_ref_dirid(leaf, ref);
184 	} else {
185 		key.objectid = found_key.offset;
186 	}
187 	btrfs_free_path(path);
188 
189 	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
190 		return btrfs_get_dentry(fs_info->sb, key.objectid,
191 					found_key.offset, 0, 0);
192 	}
193 
194 	return d_obtain_alias(btrfs_iget(fs_info->sb, key.objectid, root));
195 fail:
196 	btrfs_free_path(path);
197 	return ERR_PTR(ret);
198 }
199 
200 static int btrfs_get_name(struct dentry *parent, char *name,
201 			  struct dentry *child)
202 {
203 	struct inode *inode = d_inode(child);
204 	struct inode *dir = d_inode(parent);
205 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
206 	struct btrfs_path *path;
207 	struct btrfs_root *root = BTRFS_I(dir)->root;
208 	struct btrfs_inode_ref *iref;
209 	struct btrfs_root_ref *rref;
210 	struct extent_buffer *leaf;
211 	unsigned long name_ptr;
212 	struct btrfs_key key;
213 	int name_len;
214 	int ret;
215 	u64 ino;
216 
217 	if (!S_ISDIR(dir->i_mode))
218 		return -EINVAL;
219 
220 	ino = btrfs_ino(BTRFS_I(inode));
221 
222 	path = btrfs_alloc_path();
223 	if (!path)
224 		return -ENOMEM;
225 	path->leave_spinning = 1;
226 
227 	if (ino == BTRFS_FIRST_FREE_OBJECTID) {
228 		key.objectid = BTRFS_I(inode)->root->root_key.objectid;
229 		key.type = BTRFS_ROOT_BACKREF_KEY;
230 		key.offset = (u64)-1;
231 		root = fs_info->tree_root;
232 	} else {
233 		key.objectid = ino;
234 		key.offset = btrfs_ino(BTRFS_I(dir));
235 		key.type = BTRFS_INODE_REF_KEY;
236 	}
237 
238 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
239 	if (ret < 0) {
240 		btrfs_free_path(path);
241 		return ret;
242 	} else if (ret > 0) {
243 		if (ino == BTRFS_FIRST_FREE_OBJECTID) {
244 			path->slots[0]--;
245 		} else {
246 			btrfs_free_path(path);
247 			return -ENOENT;
248 		}
249 	}
250 	leaf = path->nodes[0];
251 
252 	if (ino == BTRFS_FIRST_FREE_OBJECTID) {
253 		rref = btrfs_item_ptr(leaf, path->slots[0],
254 				     struct btrfs_root_ref);
255 		name_ptr = (unsigned long)(rref + 1);
256 		name_len = btrfs_root_ref_name_len(leaf, rref);
257 	} else {
258 		iref = btrfs_item_ptr(leaf, path->slots[0],
259 				      struct btrfs_inode_ref);
260 		name_ptr = (unsigned long)(iref + 1);
261 		name_len = btrfs_inode_ref_name_len(leaf, iref);
262 	}
263 
264 	read_extent_buffer(leaf, name, name_ptr, name_len);
265 	btrfs_free_path(path);
266 
267 	/*
268 	 * have to add the null termination to make sure that reconnect_path
269 	 * gets the right len for strlen
270 	 */
271 	name[name_len] = '\0';
272 
273 	return 0;
274 }
275 
276 const struct export_operations btrfs_export_ops = {
277 	.encode_fh	= btrfs_encode_fh,
278 	.fh_to_dentry	= btrfs_fh_to_dentry,
279 	.fh_to_parent	= btrfs_fh_to_parent,
280 	.get_parent	= btrfs_get_parent,
281 	.get_name	= btrfs_get_name,
282 };
283