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 = BTRFS_I(inode)->location.objectid;
  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 {
  65         struct btrfs_root *root;
  66         struct inode *inode;
  67         struct btrfs_key key;
  68
  69         key.objectid = root_objectid;
  70         btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
  71         key.offset = (u64)-1;
  72
  73         root = btrfs_read_fs_root_no_name(btrfs_sb(sb)->fs_info, &key);
  74         if (IS_ERR(root))
  75                 return ERR_CAST(root);
  76
  77         key.objectid = objectid;
  78         btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
  79         key.offset = 0;
  80
  81         inode = btrfs_iget(sb, &key, root, NULL);
  82         if (IS_ERR(inode))
  83                 return (void *)inode;
  84
  85         if (generation != inode->i_generation) {
  86                 iput(inode);
  87                 return ERR_PTR(-ESTALE);
  88         }
  89
  90         return d_obtain_alias(inode);
  91 }
  92
  93 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
  94                                          int fh_len, int fh_type)
  95 {
  96         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
  97         u64 objectid, root_objectid;
  98         u32 generation;
  99
 100         if (fh_type == FILEID_BTRFS_WITH_PARENT) {
 101                 if (fh_len !=  BTRFS_FID_SIZE_CONNECTABLE)
 102                         return NULL;
 103                 root_objectid = fid->root_objectid;
 104         } else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
 105                 if (fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT)
 106                         return NULL;
 107                 root_objectid = fid->parent_root_objectid;
 108         } else
 109                 return NULL;
 110
 111         objectid = fid->parent_objectid;
 112         generation = fid->parent_gen;
 113
 114         return btrfs_get_dentry(sb, objectid, root_objectid, generation);
 115 }
 116
 117 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
 118                                          int fh_len, int fh_type)
 119 {
 120         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
 121         u64 objectid, root_objectid;
 122         u32 generation;
 123
 124         if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
 125              fh_len != BTRFS_FID_SIZE_CONNECTABLE) &&
 126             (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
 127              fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
 128             (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
 129              fh_len != BTRFS_FID_SIZE_NON_CONNECTABLE))
 130                 return NULL;
 131
 132         objectid = fid->objectid;
 133         root_objectid = fid->root_objectid;
 134         generation = fid->gen;
 135
 136         return btrfs_get_dentry(sb, objectid, root_objectid, generation);
 137 }
 138
 139 static struct dentry *btrfs_get_parent(struct dentry *child)
 140 {
 141         struct inode *dir = child->d_inode;
 142         struct btrfs_root *root = BTRFS_I(dir)->root;
 143         struct btrfs_key key;
 144         struct btrfs_path *path;
 145         struct extent_buffer *leaf;
 146         int slot;
 147         u64 objectid;
 148         int ret;
 149
 150         path = btrfs_alloc_path();
 151
 152         key.objectid = dir->i_ino;
 153         btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
 154         key.offset = (u64)-1;
 155
 156         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 157         if (ret < 0) {
 158                 /* Error */
 159                 btrfs_free_path(path);
 160                 return ERR_PTR(ret);
 161         }
 162         leaf = path->nodes[0];
 163         slot = path->slots[0];
 164         if (ret) {
 165                 /* btrfs_search_slot() returns the slot where we'd want to
 166                    insert a backref for parent inode #0xFFFFFFFFFFFFFFFF.
 167                    The _real_ backref, telling us what the parent inode
 168                    _actually_ is, will be in the slot _before_ the one
 169                    that btrfs_search_slot() returns. */
 170                 if (!slot) {
 171                         /* Unless there is _no_ key in the tree before... */
 172                         btrfs_free_path(path);
 173                         return ERR_PTR(-EIO);
 174                 }
 175                 slot--;
 176         }
 177
 178         btrfs_item_key_to_cpu(leaf, &key, slot);
 179         btrfs_free_path(path);
 180
 181         if (key.objectid != dir->i_ino || key.type != BTRFS_INODE_REF_KEY)
 182                 return ERR_PTR(-EINVAL);
 183
 184         objectid = key.offset;
 185
 186         /* If we are already at the root of a subvol, return the real root */
 187         if (objectid == dir->i_ino)
 188                 return dget(dir->i_sb->s_root);
 189
 190         /* Build a new key for the inode item */
 191         key.objectid = objectid;
 192         btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
 193         key.offset = 0;
 194
 195         return d_obtain_alias(btrfs_iget(root->fs_info->sb, &key, root, NULL));
 196 }
 197
 198 const struct export_operations btrfs_export_ops = {
 199         .encode_fh      = btrfs_encode_fh,
 200         .fh_to_dentry   = btrfs_fh_to_dentry,
 201         .fh_to_parent   = btrfs_fh_to_parent,
 202         .get_parent     = btrfs_get_parent,
 203 };