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