Root/fs/btrfs/export.c

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
16static 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
62static 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, NULL);
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;
115fail:
116    srcu_read_unlock(&fs_info->subvol_srcu, index);
117    return ERR_PTR(err);
118}
119
120static 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
144static 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
166static 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, NULL));
227    if (!IS_ERR(dentry))
228        dentry->d_op = &btrfs_dentry_operations;
229    return dentry;
230fail:
231    btrfs_free_path(path);
232    return ERR_PTR(ret);
233}
234
235const 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

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