fs/btrfs/export.c

   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
  17 static 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->root_key.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->root_key.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
  60 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
  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         root = btrfs_get_fs_root(fs_info, &key, true);
  77         if (IS_ERR(root))
  78                 return ERR_CAST(root);
  79
  80         key.objectid = objectid;
  81         key.type = BTRFS_INODE_ITEM_KEY;
  82         key.offset = 0;
  83
  84         inode = btrfs_iget(sb, &key, root);
  85         btrfs_put_root(root);
  86         if (IS_ERR(inode))
  87                 return ERR_CAST(inode);
  88
  89         if (check_generation && generation != inode->i_generation) {
  90                 iput(inode);
  91                 return ERR_PTR(-ESTALE);
  92         }
  93
  94         return d_obtain_alias(inode);
  95 }
  96
  97 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
  98                                          int fh_len, int fh_type)
  99 {
 100         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
 101         u64 objectid, root_objectid;
 102         u32 generation;
 103
 104         if (fh_type == FILEID_BTRFS_WITH_PARENT) {
 105                 if (fh_len <  BTRFS_FID_SIZE_CONNECTABLE)
 106                         return NULL;
 107                 root_objectid = fid->root_objectid;
 108         } else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
 109                 if (fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
 110                         return NULL;
 111                 root_objectid = fid->parent_root_objectid;
 112         } else
 113                 return NULL;
 114
 115         objectid = fid->parent_objectid;
 116         generation = fid->parent_gen;
 117
 118         return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
 119 }
 120
 121 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
 122                                          int fh_len, int fh_type)
 123 {
 124         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
 125         u64 objectid, root_objectid;
 126         u32 generation;
 127
 128         if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
 129              fh_len < BTRFS_FID_SIZE_CONNECTABLE) &&
 130             (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
 131              fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
 132             (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
 133              fh_len < BTRFS_FID_SIZE_NON_CONNECTABLE))
 134                 return NULL;
 135
 136         objectid = fid->objectid;
 137         root_objectid = fid->root_objectid;
 138         generation = fid->gen;
 139
 140         return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
 141 }
 142
 143 struct dentry *btrfs_get_parent(struct dentry *child)
 144 {
 145         struct inode *dir = d_inode(child);
 146         struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 147         struct btrfs_root *root = BTRFS_I(dir)->root;
 148         struct btrfs_path *path;
 149         struct extent_buffer *leaf;
 150         struct btrfs_root_ref *ref;
 151         struct btrfs_key key;
 152         struct btrfs_key found_key;
 153         int ret;
 154
 155         path = btrfs_alloc_path();
 156         if (!path)
 157                 return ERR_PTR(-ENOMEM);
 158
 159         if (btrfs_ino(BTRFS_I(dir)) == BTRFS_FIRST_FREE_OBJECTID) {
 160                 key.objectid = root->root_key.objectid;
 161                 key.type = BTRFS_ROOT_BACKREF_KEY;
 162                 key.offset = (u64)-1;
 163                 root = fs_info->tree_root;
 164         } else {
 165                 key.objectid = btrfs_ino(BTRFS_I(dir));
 166                 key.type = BTRFS_INODE_REF_KEY;
 167                 key.offset = (u64)-1;
 168         }
 169
 170         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 171         if (ret < 0)
 172                 goto fail;
 173
 174         BUG_ON(ret == 0); /* Key with offset of -1 found */
 175         if (path->slots[0] == 0) {
 176                 ret = -ENOENT;
 177                 goto fail;
 178         }
 179
 180         path->slots[0]--;
 181         leaf = path->nodes[0];
 182
 183         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 184         if (found_key.objectid != key.objectid || found_key.type != key.type) {
 185                 ret = -ENOENT;
 186                 goto fail;
 187         }
 188
 189         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 190                 ref = btrfs_item_ptr(leaf, path->slots[0],
 191                                      struct btrfs_root_ref);
 192                 key.objectid = btrfs_root_ref_dirid(leaf, ref);
 193         } else {
 194                 key.objectid = found_key.offset;
 195         }
 196         btrfs_free_path(path);
 197
 198         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 199                 return btrfs_get_dentry(fs_info->sb, key.objectid,
 200                                         found_key.offset, 0, 0);
 201         }
 202
 203         key.type = BTRFS_INODE_ITEM_KEY;
 204         key.offset = 0;
 205         return d_obtain_alias(btrfs_iget(fs_info->sb, &key, root));
 206 fail:
 207         btrfs_free_path(path);
 208         return ERR_PTR(ret);
 209 }
 210
 211 static int btrfs_get_name(struct dentry *parent, char *name,
 212                           struct dentry *child)
 213 {
 214         struct inode *inode = d_inode(child);
 215         struct inode *dir = d_inode(parent);
 216         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 217         struct btrfs_path *path;
 218         struct btrfs_root *root = BTRFS_I(dir)->root;
 219         struct btrfs_inode_ref *iref;
 220         struct btrfs_root_ref *rref;
 221         struct extent_buffer *leaf;
 222         unsigned long name_ptr;
 223         struct btrfs_key key;
 224         int name_len;
 225         int ret;
 226         u64 ino;
 227
 228         if (!S_ISDIR(dir->i_mode))
 229                 return -EINVAL;
 230
 231         ino = btrfs_ino(BTRFS_I(inode));
 232
 233         path = btrfs_alloc_path();
 234         if (!path)
 235                 return -ENOMEM;
 236         path->leave_spinning = 1;
 237
 238         if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 239                 key.objectid = BTRFS_I(inode)->root->root_key.objectid;
 240                 key.type = BTRFS_ROOT_BACKREF_KEY;
 241                 key.offset = (u64)-1;
 242                 root = fs_info->tree_root;
 243         } else {
 244                 key.objectid = ino;
 245                 key.offset = btrfs_ino(BTRFS_I(dir));
 246                 key.type = BTRFS_INODE_REF_KEY;
 247         }
 248
 249         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 250         if (ret < 0) {
 251                 btrfs_free_path(path);
 252                 return ret;
 253         } else if (ret > 0) {
 254                 if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 255                         path->slots[0]--;
 256                 } else {
 257                         btrfs_free_path(path);
 258                         return -ENOENT;
 259                 }
 260         }
 261         leaf = path->nodes[0];
 262
 263         if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 264                 rref = btrfs_item_ptr(leaf, path->slots[0],
 265                                      struct btrfs_root_ref);
 266                 name_ptr = (unsigned long)(rref + 1);
 267                 name_len = btrfs_root_ref_name_len(leaf, rref);
 268         } else {
 269                 iref = btrfs_item_ptr(leaf, path->slots[0],
 270                                       struct btrfs_inode_ref);
 271                 name_ptr = (unsigned long)(iref + 1);
 272                 name_len = btrfs_inode_ref_name_len(leaf, iref);
 273         }
 274
 275         read_extent_buffer(leaf, name, name_ptr, name_len);
 276         btrfs_free_path(path);
 277
 278         /*
 279          * have to add the null termination to make sure that reconnect_path
 280          * gets the right len for strlen
 281          */
 282         name[name_len] = '\0';
 283
 284         return 0;
 285 }
 286
 287 const struct export_operations btrfs_export_ops = {
 288         .encode_fh      = btrfs_encode_fh,
 289         .fh_to_dentry   = btrfs_fh_to_dentry,
 290         .fh_to_parent   = btrfs_fh_to_parent,
 291         .get_parent     = btrfs_get_parent,
 292         .get_name       = btrfs_get_name,
 293 };