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