xref: /openbmc/linux/fs/btrfs/export.c (revision 4800cd83)
1 #include <linux/fs.h>
2 #include <linux/types.h>
3 #include "ctree.h"
4 #include "disk-io.h"
5 #include "btrfs_inode.h"
6 #include "print-tree.h"
7 #include "export.h"
8 #include "compat.h"
9 
10 #define BTRFS_FID_SIZE_NON_CONNECTABLE (offsetof(struct btrfs_fid, \
11 						 parent_objectid) / 4)
12 #define BTRFS_FID_SIZE_CONNECTABLE (offsetof(struct btrfs_fid, \
13 					     parent_root_objectid) / 4)
14 #define BTRFS_FID_SIZE_CONNECTABLE_ROOT (sizeof(struct btrfs_fid) / 4)
15 
16 static int btrfs_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
17 			   int connectable)
18 {
19 	struct btrfs_fid *fid = (struct btrfs_fid *)fh;
20 	struct inode *inode = dentry->d_inode;
21 	int len = *max_len;
22 	int type;
23 
24 	if ((len < BTRFS_FID_SIZE_NON_CONNECTABLE) ||
25 	    (connectable && len < BTRFS_FID_SIZE_CONNECTABLE))
26 		return 255;
27 
28 	len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
29 	type = FILEID_BTRFS_WITHOUT_PARENT;
30 
31 	fid->objectid = inode->i_ino;
32 	fid->root_objectid = BTRFS_I(inode)->root->objectid;
33 	fid->gen = inode->i_generation;
34 
35 	if (connectable && !S_ISDIR(inode->i_mode)) {
36 		struct inode *parent;
37 		u64 parent_root_id;
38 
39 		spin_lock(&dentry->d_lock);
40 
41 		parent = dentry->d_parent->d_inode;
42 		fid->parent_objectid = BTRFS_I(parent)->location.objectid;
43 		fid->parent_gen = parent->i_generation;
44 		parent_root_id = BTRFS_I(parent)->root->objectid;
45 
46 		spin_unlock(&dentry->d_lock);
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 static struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
63 				       u64 root_objectid, u32 generation,
64 				       int check_generation)
65 {
66 	struct btrfs_fs_info *fs_info = btrfs_sb(sb)->fs_info;
67 	struct btrfs_root *root;
68 	struct inode *inode;
69 	struct btrfs_key key;
70 	int index;
71 	int err = 0;
72 
73 	if (objectid < BTRFS_FIRST_FREE_OBJECTID)
74 		return ERR_PTR(-ESTALE);
75 
76 	key.objectid = root_objectid;
77 	btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
78 	key.offset = (u64)-1;
79 
80 	index = srcu_read_lock(&fs_info->subvol_srcu);
81 
82 	root = btrfs_read_fs_root_no_name(fs_info, &key);
83 	if (IS_ERR(root)) {
84 		err = PTR_ERR(root);
85 		goto fail;
86 	}
87 
88 	if (btrfs_root_refs(&root->root_item) == 0) {
89 		err = -ENOENT;
90 		goto fail;
91 	}
92 
93 	key.objectid = objectid;
94 	btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
95 	key.offset = 0;
96 
97 	inode = btrfs_iget(sb, &key, root, NULL);
98 	if (IS_ERR(inode)) {
99 		err = PTR_ERR(inode);
100 		goto fail;
101 	}
102 
103 	srcu_read_unlock(&fs_info->subvol_srcu, index);
104 
105 	if (check_generation && generation != inode->i_generation) {
106 		iput(inode);
107 		return ERR_PTR(-ESTALE);
108 	}
109 
110 	return d_obtain_alias(inode);
111 fail:
112 	srcu_read_unlock(&fs_info->subvol_srcu, index);
113 	return ERR_PTR(err);
114 }
115 
116 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
117 					 int fh_len, int fh_type)
118 {
119 	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
120 	u64 objectid, root_objectid;
121 	u32 generation;
122 
123 	if (fh_type == FILEID_BTRFS_WITH_PARENT) {
124 		if (fh_len !=  BTRFS_FID_SIZE_CONNECTABLE)
125 			return NULL;
126 		root_objectid = fid->root_objectid;
127 	} else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
128 		if (fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT)
129 			return NULL;
130 		root_objectid = fid->parent_root_objectid;
131 	} else
132 		return NULL;
133 
134 	objectid = fid->parent_objectid;
135 	generation = fid->parent_gen;
136 
137 	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
138 }
139 
140 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
141 					 int fh_len, int fh_type)
142 {
143 	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
144 	u64 objectid, root_objectid;
145 	u32 generation;
146 
147 	if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
148 	     fh_len != BTRFS_FID_SIZE_CONNECTABLE) &&
149 	    (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
150 	     fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
151 	    (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
152 	     fh_len != BTRFS_FID_SIZE_NON_CONNECTABLE))
153 		return NULL;
154 
155 	objectid = fid->objectid;
156 	root_objectid = fid->root_objectid;
157 	generation = fid->gen;
158 
159 	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
160 }
161 
162 static struct dentry *btrfs_get_parent(struct dentry *child)
163 {
164 	struct inode *dir = child->d_inode;
165 	struct btrfs_root *root = BTRFS_I(dir)->root;
166 	struct btrfs_path *path;
167 	struct extent_buffer *leaf;
168 	struct btrfs_root_ref *ref;
169 	struct btrfs_key key;
170 	struct btrfs_key found_key;
171 	int ret;
172 
173 	path = btrfs_alloc_path();
174 	if (!path)
175 		return ERR_PTR(-ENOMEM);
176 
177 	if (dir->i_ino == BTRFS_FIRST_FREE_OBJECTID) {
178 		key.objectid = root->root_key.objectid;
179 		key.type = BTRFS_ROOT_BACKREF_KEY;
180 		key.offset = (u64)-1;
181 		root = root->fs_info->tree_root;
182 	} else {
183 		key.objectid = dir->i_ino;
184 		key.type = BTRFS_INODE_REF_KEY;
185 		key.offset = (u64)-1;
186 	}
187 
188 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
189 	if (ret < 0)
190 		goto fail;
191 
192 	BUG_ON(ret == 0);
193 	if (path->slots[0] == 0) {
194 		ret = -ENOENT;
195 		goto fail;
196 	}
197 
198 	path->slots[0]--;
199 	leaf = path->nodes[0];
200 
201 	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
202 	if (found_key.objectid != key.objectid || found_key.type != key.type) {
203 		ret = -ENOENT;
204 		goto fail;
205 	}
206 
207 	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
208 		ref = btrfs_item_ptr(leaf, path->slots[0],
209 				     struct btrfs_root_ref);
210 		key.objectid = btrfs_root_ref_dirid(leaf, ref);
211 	} else {
212 		key.objectid = found_key.offset;
213 	}
214 	btrfs_free_path(path);
215 
216 	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
217 		return btrfs_get_dentry(root->fs_info->sb, key.objectid,
218 					found_key.offset, 0, 0);
219 	}
220 
221 	key.type = BTRFS_INODE_ITEM_KEY;
222 	key.offset = 0;
223 	return d_obtain_alias(btrfs_iget(root->fs_info->sb, &key, root, NULL));
224 fail:
225 	btrfs_free_path(path);
226 	return ERR_PTR(ret);
227 }
228 
229 static int btrfs_get_name(struct dentry *parent, char *name,
230 			  struct dentry *child)
231 {
232 	struct inode *inode = child->d_inode;
233 	struct inode *dir = parent->d_inode;
234 	struct btrfs_path *path;
235 	struct btrfs_root *root = BTRFS_I(dir)->root;
236 	struct btrfs_inode_ref *iref;
237 	struct btrfs_root_ref *rref;
238 	struct extent_buffer *leaf;
239 	unsigned long name_ptr;
240 	struct btrfs_key key;
241 	int name_len;
242 	int ret;
243 
244 	if (!dir || !inode)
245 		return -EINVAL;
246 
247 	if (!S_ISDIR(dir->i_mode))
248 		return -EINVAL;
249 
250 	path = btrfs_alloc_path();
251 	if (!path)
252 		return -ENOMEM;
253 	path->leave_spinning = 1;
254 
255 	if (inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) {
256 		key.objectid = BTRFS_I(inode)->root->root_key.objectid;
257 		key.type = BTRFS_ROOT_BACKREF_KEY;
258 		key.offset = (u64)-1;
259 		root = root->fs_info->tree_root;
260 	} else {
261 		key.objectid = inode->i_ino;
262 		key.offset = dir->i_ino;
263 		key.type = BTRFS_INODE_REF_KEY;
264 	}
265 
266 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
267 	if (ret < 0) {
268 		btrfs_free_path(path);
269 		return ret;
270 	} else if (ret > 0) {
271 		if (inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) {
272 			path->slots[0]--;
273 		} else {
274 			btrfs_free_path(path);
275 			return -ENOENT;
276 		}
277 	}
278 	leaf = path->nodes[0];
279 
280 	if (inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) {
281 	       rref = btrfs_item_ptr(leaf, path->slots[0],
282 				     struct btrfs_root_ref);
283 	       name_ptr = (unsigned long)(rref + 1);
284 	       name_len = btrfs_root_ref_name_len(leaf, rref);
285 	} else {
286 		iref = btrfs_item_ptr(leaf, path->slots[0],
287 				      struct btrfs_inode_ref);
288 		name_ptr = (unsigned long)(iref + 1);
289 		name_len = btrfs_inode_ref_name_len(leaf, iref);
290 	}
291 
292 	read_extent_buffer(leaf, name, name_ptr, name_len);
293 	btrfs_free_path(path);
294 
295 	/*
296 	 * have to add the null termination to make sure that reconnect_path
297 	 * gets the right len for strlen
298 	 */
299 	name[name_len] = '\0';
300 
301 	return 0;
302 }
303 
304 const struct export_operations btrfs_export_ops = {
305 	.encode_fh	= btrfs_encode_fh,
306 	.fh_to_dentry	= btrfs_fh_to_dentry,
307 	.fh_to_parent	= btrfs_fh_to_parent,
308 	.get_parent	= btrfs_get_parent,
309 	.get_name	= btrfs_get_name,
310 };
311