fs/btrfs/export.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/fs.h>
   3 #include <linux/types.h>
   4 #include "ctree.h"
   5 #include "disk-io.h"
   6 #include "btrfs_inode.h"
   7 #include "print-tree.h"
   8 #include "export.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 inode *inode, u32 *fh, int *max_len,
  17                            struct inode *parent)
  18 {
  19         struct btrfs_fid *fid = (struct btrfs_fid *)fh;
  20         int len = *max_len;
  21         int type;
  22
  23         if (parent && (len < BTRFS_FID_SIZE_CONNECTABLE)) {
  24                 *max_len = BTRFS_FID_SIZE_CONNECTABLE;
  25                 return FILEID_INVALID;
  26         } else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
  27                 *max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;
  28                 return FILEID_INVALID;
  29         }
  30
  31         len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
  32         type = FILEID_BTRFS_WITHOUT_PARENT;
  33
  34         fid->objectid = btrfs_ino(BTRFS_I(inode));
  35         fid->root_objectid = BTRFS_I(inode)->root->objectid;
  36         fid->gen = inode->i_generation;
  37
  38         if (parent) {
  39                 u64 parent_root_id;
  40
  41                 fid->parent_objectid = BTRFS_I(parent)->location.objectid;
  42                 fid->parent_gen = parent->i_generation;
  43                 parent_root_id = BTRFS_I(parent)->root->objectid;
  44
  45                 if (parent_root_id != fid->root_objectid) {
  46                         fid->parent_root_objectid = parent_root_id;
  47                         len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
  48                         type = FILEID_BTRFS_WITH_PARENT_ROOT;
  49                 } else {
  50                         len = BTRFS_FID_SIZE_CONNECTABLE;
  51                         type = FILEID_BTRFS_WITH_PARENT;
  52                 }
  53         }
  54
  55         *max_len = len;
  56         return type;
  57 }
  58
  59 static struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
  60                                        u64 root_objectid, u32 generation,
  61                                        int check_generation)
  62 {
  63         struct btrfs_fs_info *fs_info = btrfs_sb(sb);
  64         struct btrfs_root *root;
  65         struct inode *inode;
  66         struct btrfs_key key;
  67         int index;
  68         int err = 0;
  69
  70         if (objectid < BTRFS_FIRST_FREE_OBJECTID)
  71                 return ERR_PTR(-ESTALE);
  72
  73         key.objectid = root_objectid;
  74         key.type = BTRFS_ROOT_ITEM_KEY;
  75         key.offset = (u64)-1;
  76
  77         index = srcu_read_lock(&fs_info->subvol_srcu);
  78
  79         root = btrfs_read_fs_root_no_name(fs_info, &key);
  80         if (IS_ERR(root)) {
  81                 err = PTR_ERR(root);
  82                 goto fail;
  83         }
  84
  85         key.objectid = objectid;
  86         key.type = BTRFS_INODE_ITEM_KEY;
  87         key.offset = 0;
  88
  89         inode = btrfs_iget(sb, &key, root, NULL);
  90         if (IS_ERR(inode)) {
  91                 err = PTR_ERR(inode);
  92                 goto fail;
  93         }
  94
  95         srcu_read_unlock(&fs_info->subvol_srcu, index);
  96
  97         if (check_generation && generation != inode->i_generation) {
  98                 iput(inode);
  99                 return ERR_PTR(-ESTALE);
 100         }
 101
 102         return d_obtain_alias(inode);
 103 fail:
 104         srcu_read_unlock(&fs_info->subvol_srcu, index);
 105         return ERR_PTR(err);
 106 }
 107
 108 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
 109                                          int fh_len, int fh_type)
 110 {
 111         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
 112         u64 objectid, root_objectid;
 113         u32 generation;
 114
 115         if (fh_type == FILEID_BTRFS_WITH_PARENT) {
 116                 if (fh_len <  BTRFS_FID_SIZE_CONNECTABLE)
 117                         return NULL;
 118                 root_objectid = fid->root_objectid;
 119         } else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
 120                 if (fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
 121                         return NULL;
 122                 root_objectid = fid->parent_root_objectid;
 123         } else
 124                 return NULL;
 125
 126         objectid = fid->parent_objectid;
 127         generation = fid->parent_gen;
 128
 129         return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
 130 }
 131
 132 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
 133                                          int fh_len, int fh_type)
 134 {
 135         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
 136         u64 objectid, root_objectid;
 137         u32 generation;
 138
 139         if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
 140              fh_len < BTRFS_FID_SIZE_CONNECTABLE) &&
 141             (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
 142              fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
 143             (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
 144              fh_len < BTRFS_FID_SIZE_NON_CONNECTABLE))
 145                 return NULL;
 146
 147         objectid = fid->objectid;
 148         root_objectid = fid->root_objectid;
 149         generation = fid->gen;
 150
 151         return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
 152 }
 153
 154 static struct dentry *btrfs_get_parent(struct dentry *child)
 155 {
 156         struct inode *dir = d_inode(child);
 157         struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 158         struct btrfs_root *root = BTRFS_I(dir)->root;
 159         struct btrfs_path *path;
 160         struct extent_buffer *leaf;
 161         struct btrfs_root_ref *ref;
 162         struct btrfs_key key;
 163         struct btrfs_key found_key;
 164         int ret;
 165
 166         path = btrfs_alloc_path();
 167         if (!path)
 168                 return ERR_PTR(-ENOMEM);
 169
 170         if (btrfs_ino(BTRFS_I(dir)) == BTRFS_FIRST_FREE_OBJECTID) {
 171                 key.objectid = root->root_key.objectid;
 172                 key.type = BTRFS_ROOT_BACKREF_KEY;
 173                 key.offset = (u64)-1;
 174                 root = fs_info->tree_root;
 175         } else {
 176                 key.objectid = btrfs_ino(BTRFS_I(dir));
 177                 key.type = BTRFS_INODE_REF_KEY;
 178                 key.offset = (u64)-1;
 179         }
 180
 181         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 182         if (ret < 0)
 183                 goto fail;
 184
 185         BUG_ON(ret == 0); /* Key with offset of -1 found */
 186         if (path->slots[0] == 0) {
 187                 ret = -ENOENT;
 188                 goto fail;
 189         }
 190
 191         path->slots[0]--;
 192         leaf = path->nodes[0];
 193
 194         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 195         if (found_key.objectid != key.objectid || found_key.type != key.type) {
 196                 ret = -ENOENT;
 197                 goto fail;
 198         }
 199
 200         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 201                 ref = btrfs_item_ptr(leaf, path->slots[0],
 202                                      struct btrfs_root_ref);
 203                 key.objectid = btrfs_root_ref_dirid(leaf, ref);
 204         } else {
 205                 key.objectid = found_key.offset;
 206         }
 207         btrfs_free_path(path);
 208
 209         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 210                 return btrfs_get_dentry(fs_info->sb, key.objectid,
 211                                         found_key.offset, 0, 0);
 212         }
 213
 214         key.type = BTRFS_INODE_ITEM_KEY;
 215         key.offset = 0;
 216         return d_obtain_alias(btrfs_iget(fs_info->sb, &key, root, NULL));
 217 fail:
 218         btrfs_free_path(path);
 219         return ERR_PTR(ret);
 220 }
 221
 222 static int btrfs_get_name(struct dentry *parent, char *name,
 223                           struct dentry *child)
 224 {
 225         struct inode *inode = d_inode(child);
 226         struct inode *dir = d_inode(parent);
 227         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 228         struct btrfs_path *path;
 229         struct btrfs_root *root = BTRFS_I(dir)->root;
 230         struct btrfs_inode_ref *iref;
 231         struct btrfs_root_ref *rref;
 232         struct extent_buffer *leaf;
 233         unsigned long name_ptr;
 234         struct btrfs_key key;
 235         int name_len;
 236         int ret;
 237         u64 ino;
 238
 239         if (!S_ISDIR(dir->i_mode))
 240                 return -EINVAL;
 241
 242         ino = btrfs_ino(BTRFS_I(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 = fs_info->tree_root;
 254         } else {
 255                 key.objectid = ino;
 256                 key.offset = btrfs_ino(BTRFS_I(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
 298 const 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 };