export.c

  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 "export.h"
  9#include "accessors.h"
 10#include "super.h"
 11
 12#define BTRFS_FID_SIZE_NON_CONNECTABLE (offsetof(struct btrfs_fid, \
 13						 parent_objectid) / 4)
 14#define BTRFS_FID_SIZE_CONNECTABLE (offsetof(struct btrfs_fid, \
 15					     parent_root_objectid) / 4)
 16#define BTRFS_FID_SIZE_CONNECTABLE_ROOT (sizeof(struct btrfs_fid) / 4)
 17
 18static int btrfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
 19			   struct inode *parent)
 20{
 21	struct btrfs_fid *fid = (struct btrfs_fid *)fh;
 22	int len = *max_len;
 23	int type;
 24
 25	if (parent && (len < BTRFS_FID_SIZE_CONNECTABLE)) {
 26		if (btrfs_root_id(BTRFS_I(inode)->root) !=
 27		    btrfs_root_id(BTRFS_I(parent)->root))
 28			*max_len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
 29		else
 30			*max_len = BTRFS_FID_SIZE_CONNECTABLE;
 31		return FILEID_INVALID;
 32	} else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
 33		*max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;
 34		return FILEID_INVALID;
 35	}
 36
 37	len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
 38	type = FILEID_BTRFS_WITHOUT_PARENT;
 39
 40	fid->objectid = btrfs_ino(BTRFS_I(inode));
 41	fid->root_objectid = btrfs_root_id(BTRFS_I(inode)->root);
 42	fid->gen = inode->i_generation;
 43
 44	if (parent) {
 45		u64 parent_root_id;
 46
 47		fid->parent_objectid = btrfs_ino(BTRFS_I(parent));
 48		fid->parent_gen = parent->i_generation;
 49		parent_root_id = btrfs_root_id(BTRFS_I(parent)->root);
 50
 51		if (parent_root_id != fid->root_objectid) {
 52			if (*max_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
 53				return FILEID_INVALID;
 54			fid->parent_root_objectid = parent_root_id;
 55			len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
 56			type = FILEID_BTRFS_WITH_PARENT_ROOT;
 57		} else {
 58			len = BTRFS_FID_SIZE_CONNECTABLE;
 59			type = FILEID_BTRFS_WITH_PARENT;
 60		}
 61	}
 62
 63	*max_len = len;
 64	return type;
 65}
 66
 67/*
 68 * Read dentry of inode with @objectid from filesystem root @root_objectid.
 69 *
 70 * @sb:             the filesystem super block
 71 * @objectid:       inode objectid
 72 * @root_objectid:  object id of the subvolume root where to look up the inode
 73 * @generation:     optional, if not zero, verify that the found inode
 74 *                  generation matches
 75 *
 76 * Return dentry alias for the inode, otherwise an error. In case the
 77 * generation does not match return ESTALE.
 78 */
 79struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
 80				u64 root_objectid, u64 generation)
 81{
 82	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
 83	struct btrfs_root *root;
 84	struct btrfs_inode *inode;
 85
 86	if (objectid < BTRFS_FIRST_FREE_OBJECTID)
 87		return ERR_PTR(-ESTALE);
 88
 89	root = btrfs_get_fs_root(fs_info, root_objectid, true);
 90	if (IS_ERR(root))
 91		return ERR_CAST(root);
 92
 93	inode = btrfs_iget(objectid, root);
 94	btrfs_put_root(root);
 95	if (IS_ERR(inode))
 96		return ERR_CAST(inode);
 97
 98	if (generation != 0 && generation != inode->vfs_inode.i_generation) {
 99		iput(&inode->vfs_inode);
100		return ERR_PTR(-ESTALE);
101	}
102
103	return d_obtain_alias(&inode->vfs_inode);
104}
105
106static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
107					 int fh_len, int fh_type)
108{
109	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
110	u64 objectid, root_objectid;
111	u32 generation;
112
113	if (fh_type == FILEID_BTRFS_WITH_PARENT) {
114		if (fh_len <  BTRFS_FID_SIZE_CONNECTABLE)
115			return NULL;
116		root_objectid = fid->root_objectid;
117	} else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
118		if (fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
119			return NULL;
120		root_objectid = fid->parent_root_objectid;
121	} else
122		return NULL;
123
124	objectid = fid->parent_objectid;
125	generation = fid->parent_gen;
126
127	return btrfs_get_dentry(sb, objectid, root_objectid, generation);
128}
129
130static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
131					 int fh_len, int fh_type)
132{
133	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
134	u64 objectid, root_objectid;
135	u32 generation;
136
137	if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
138	     fh_len < BTRFS_FID_SIZE_CONNECTABLE) &&
139	    (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
140	     fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
141	    (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
142	     fh_len < BTRFS_FID_SIZE_NON_CONNECTABLE))
143		return NULL;
144
145	objectid = fid->objectid;
146	root_objectid = fid->root_objectid;
147	generation = fid->gen;
148
149	return btrfs_get_dentry(sb, objectid, root_objectid, generation);
150}
151
152struct dentry *btrfs_get_parent(struct dentry *child)
153{
154	struct btrfs_inode *dir = BTRFS_I(d_inode(child));
155	struct btrfs_inode *inode;
156	struct btrfs_root *root = dir->root;
157	struct btrfs_fs_info *fs_info = root->fs_info;
158	struct btrfs_path *path;
159	struct extent_buffer *leaf;
160	struct btrfs_root_ref *ref;
161	struct btrfs_key key;
162	struct btrfs_key found_key;
163	int ret;
164
165	path = btrfs_alloc_path();
166	if (!path)
167		return ERR_PTR(-ENOMEM);
168
169	if (btrfs_ino(dir) == BTRFS_FIRST_FREE_OBJECTID) {
170		key.objectid = btrfs_root_id(root);
171		key.type = BTRFS_ROOT_BACKREF_KEY;
172		key.offset = (u64)-1;
173		root = fs_info->tree_root;
174	} else {
175		key.objectid = btrfs_ino(dir);
176		key.type = BTRFS_INODE_REF_KEY;
177		key.offset = (u64)-1;
178	}
179
180	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
181	if (ret < 0)
182		goto fail;
183	if (unlikely(ret == 0)) {
184		/*
185		 * Key with offset of -1 found, there would have to exist an
186		 * inode with such number or a root with such id.
187		 */
188		ret = -EUCLEAN;
189		goto fail;
190	}
191
192	if (path->slots[0] == 0) {
193		ret = -ENOENT;
194		goto fail;
195	}
196
197	path->slots[0]--;
198	leaf = path->nodes[0];
199
200	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
201	if (found_key.objectid != key.objectid || found_key.type != key.type) {
202		ret = -ENOENT;
203		goto fail;
204	}
205
206	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
207		ref = btrfs_item_ptr(leaf, path->slots[0],
208				     struct btrfs_root_ref);
209		key.objectid = btrfs_root_ref_dirid(leaf, ref);
210	} else {
211		key.objectid = found_key.offset;
212	}
213	btrfs_free_path(path);
214
215	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
216		return btrfs_get_dentry(fs_info->sb, key.objectid,
217					found_key.offset, 0);
218	}
219
220	inode = btrfs_iget(key.objectid, root);
221	if (IS_ERR(inode))
222		return ERR_CAST(inode);
223
224	return d_obtain_alias(&inode->vfs_inode);
225fail:
226	btrfs_free_path(path);
227	return ERR_PTR(ret);
228}
229
230static int btrfs_get_name(struct dentry *parent, char *name,
231			  struct dentry *child)
232{
233	struct btrfs_inode *inode = BTRFS_I(d_inode(child));
234	struct btrfs_inode *dir = BTRFS_I(d_inode(parent));
235	struct btrfs_root *root = dir->root;
236	struct btrfs_fs_info *fs_info = root->fs_info;
237	BTRFS_PATH_AUTO_FREE(path);
238	struct btrfs_inode_ref *iref;
239	struct btrfs_root_ref *rref;
240	struct extent_buffer *leaf;
241	unsigned long name_ptr;
242	struct btrfs_key key;
243	int name_len;
244	int ret;
245	u64 ino;
246
247	if (!S_ISDIR(dir->vfs_inode.i_mode))
248		return -EINVAL;
249
250	ino = btrfs_ino(inode);
251
252	path = btrfs_alloc_path();
253	if (!path)
254		return -ENOMEM;
255
256	if (ino == BTRFS_FIRST_FREE_OBJECTID) {
257		key.objectid = btrfs_root_id(inode->root);
258		key.type = BTRFS_ROOT_BACKREF_KEY;
259		key.offset = (u64)-1;
260		root = fs_info->tree_root;
261	} else {
262		key.objectid = ino;
263		key.type = BTRFS_INODE_REF_KEY;
264		key.offset = btrfs_ino(dir);
265	}
266
267	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
268	if (ret < 0) {
269		return ret;
270	} else if (ret > 0) {
271		if (ino == BTRFS_FIRST_FREE_OBJECTID)
272			path->slots[0]--;
273		else
274			return -ENOENT;
275	}
276	leaf = path->nodes[0];
277
278	if (ino == BTRFS_FIRST_FREE_OBJECTID) {
279		rref = btrfs_item_ptr(leaf, path->slots[0],
280				     struct btrfs_root_ref);
281		name_ptr = (unsigned long)(rref + 1);
282		name_len = btrfs_root_ref_name_len(leaf, rref);
283	} else {
284		iref = btrfs_item_ptr(leaf, path->slots[0],
285				      struct btrfs_inode_ref);
286		name_ptr = (unsigned long)(iref + 1);
287		name_len = btrfs_inode_ref_name_len(leaf, iref);
288	}
289
290	read_extent_buffer(leaf, name, name_ptr, name_len);
291
292	/*
293	 * have to add the null termination to make sure that reconnect_path
294	 * gets the right len for strlen
295	 */
296	name[name_len] = '\0';
297
298	return 0;
299}
300
301const struct export_operations btrfs_export_ops = {
302	.encode_fh	= btrfs_encode_fh,
303	.fh_to_dentry	= btrfs_fh_to_dentry,
304	.fh_to_parent	= btrfs_fh_to_parent,
305	.get_parent	= btrfs_get_parent,
306	.get_name	= btrfs_get_name,
307};