xref: /openbmc/linux/fs/btrfs/export.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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 dentry *dentry;
69 	struct inode *inode;
70 	struct btrfs_key key;
71 	int index;
72 	int err = 0;
73 
74 	if (objectid < BTRFS_FIRST_FREE_OBJECTID)
75 		return ERR_PTR(-ESTALE);
76 
77 	key.objectid = root_objectid;
78 	btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
79 	key.offset = (u64)-1;
80 
81 	index = srcu_read_lock(&fs_info->subvol_srcu);
82 
83 	root = btrfs_read_fs_root_no_name(fs_info, &key);
84 	if (IS_ERR(root)) {
85 		err = PTR_ERR(root);
86 		goto fail;
87 	}
88 
89 	if (btrfs_root_refs(&root->root_item) == 0) {
90 		err = -ENOENT;
91 		goto fail;
92 	}
93 
94 	key.objectid = objectid;
95 	btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
96 	key.offset = 0;
97 
98 	inode = btrfs_iget(sb, &key, root);
99 	if (IS_ERR(inode)) {
100 		err = PTR_ERR(inode);
101 		goto fail;
102 	}
103 
104 	srcu_read_unlock(&fs_info->subvol_srcu, index);
105 
106 	if (check_generation && generation != inode->i_generation) {
107 		iput(inode);
108 		return ERR_PTR(-ESTALE);
109 	}
110 
111 	dentry = d_obtain_alias(inode);
112 	if (!IS_ERR(dentry))
113 		dentry->d_op = &btrfs_dentry_operations;
114 	return dentry;
115 fail:
116 	srcu_read_unlock(&fs_info->subvol_srcu, index);
117 	return ERR_PTR(err);
118 }
119 
120 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
121 					 int fh_len, int fh_type)
122 {
123 	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
124 	u64 objectid, root_objectid;
125 	u32 generation;
126 
127 	if (fh_type == FILEID_BTRFS_WITH_PARENT) {
128 		if (fh_len !=  BTRFS_FID_SIZE_CONNECTABLE)
129 			return NULL;
130 		root_objectid = fid->root_objectid;
131 	} else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
132 		if (fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT)
133 			return NULL;
134 		root_objectid = fid->parent_root_objectid;
135 	} else
136 		return NULL;
137 
138 	objectid = fid->parent_objectid;
139 	generation = fid->parent_gen;
140 
141 	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
142 }
143 
144 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
145 					 int fh_len, int fh_type)
146 {
147 	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
148 	u64 objectid, root_objectid;
149 	u32 generation;
150 
151 	if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
152 	     fh_len != BTRFS_FID_SIZE_CONNECTABLE) &&
153 	    (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
154 	     fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
155 	    (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
156 	     fh_len != BTRFS_FID_SIZE_NON_CONNECTABLE))
157 		return NULL;
158 
159 	objectid = fid->objectid;
160 	root_objectid = fid->root_objectid;
161 	generation = fid->gen;
162 
163 	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
164 }
165 
166 static struct dentry *btrfs_get_parent(struct dentry *child)
167 {
168 	struct inode *dir = child->d_inode;
169 	static struct dentry *dentry;
170 	struct btrfs_root *root = BTRFS_I(dir)->root;
171 	struct btrfs_path *path;
172 	struct extent_buffer *leaf;
173 	struct btrfs_root_ref *ref;
174 	struct btrfs_key key;
175 	struct btrfs_key found_key;
176 	int ret;
177 
178 	path = btrfs_alloc_path();
179 
180 	if (dir->i_ino == BTRFS_FIRST_FREE_OBJECTID) {
181 		key.objectid = root->root_key.objectid;
182 		key.type = BTRFS_ROOT_BACKREF_KEY;
183 		key.offset = (u64)-1;
184 		root = root->fs_info->tree_root;
185 	} else {
186 		key.objectid = dir->i_ino;
187 		key.type = BTRFS_INODE_REF_KEY;
188 		key.offset = (u64)-1;
189 	}
190 
191 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
192 	if (ret < 0)
193 		goto fail;
194 
195 	BUG_ON(ret == 0);
196 	if (path->slots[0] == 0) {
197 		ret = -ENOENT;
198 		goto fail;
199 	}
200 
201 	path->slots[0]--;
202 	leaf = path->nodes[0];
203 
204 	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
205 	if (found_key.objectid != key.objectid || found_key.type != key.type) {
206 		ret = -ENOENT;
207 		goto fail;
208 	}
209 
210 	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
211 		ref = btrfs_item_ptr(leaf, path->slots[0],
212 				     struct btrfs_root_ref);
213 		key.objectid = btrfs_root_ref_dirid(leaf, ref);
214 	} else {
215 		key.objectid = found_key.offset;
216 	}
217 	btrfs_free_path(path);
218 
219 	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
220 		return btrfs_get_dentry(root->fs_info->sb, key.objectid,
221 					found_key.offset, 0, 0);
222 	}
223 
224 	key.type = BTRFS_INODE_ITEM_KEY;
225 	key.offset = 0;
226 	dentry = d_obtain_alias(btrfs_iget(root->fs_info->sb, &key, root));
227 	if (!IS_ERR(dentry))
228 		dentry->d_op = &btrfs_dentry_operations;
229 	return dentry;
230 fail:
231 	btrfs_free_path(path);
232 	return ERR_PTR(ret);
233 }
234 
235 const struct export_operations btrfs_export_ops = {
236 	.encode_fh	= btrfs_encode_fh,
237 	.fh_to_dentry	= btrfs_fh_to_dentry,
238 	.fh_to_parent	= btrfs_fh_to_parent,
239 	.get_parent	= btrfs_get_parent,
240 };
241