xref: /openbmc/linux/fs/btrfs/export.c (revision 051d4420)
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  
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   */
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  
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  
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  
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  
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