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
  16 static 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
  62 static 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;
 115 fail:
 116         srcu_read_unlock(&fs_info->subvol_srcu, index);
 117         return ERR_PTR(err);
 118 }
 119
 120 static 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
 144 static 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
 166 static 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;
 230 fail:
 231         btrfs_free_path(path);
 232         return ERR_PTR(ret);
 233 }
 234
 235 const 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 };