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, u64 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
  68         if (objectid < BTRFS_FIRST_FREE_OBJECTID)
  69                 return ERR_PTR(-ESTALE);
  70
  71         root = btrfs_get_fs_root(fs_info, root_objectid, true);
  72         if (IS_ERR(root))
  73                 return ERR_CAST(root);
  74
  75         inode = btrfs_iget(sb, objectid, root);
  76         btrfs_put_root(root);
  77         if (IS_ERR(inode))
  78                 return ERR_CAST(inode);
  79
  80         if (check_generation && generation != inode->i_generation) {
  81                 iput(inode);
  82                 return ERR_PTR(-ESTALE);
  83         }
  84
  85         return d_obtain_alias(inode);
  86 }
  87
  88 static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
  89                                          int fh_len, int fh_type)
  90 {
  91         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
  92         u64 objectid, root_objectid;
  93         u32 generation;
  94
  95         if (fh_type == FILEID_BTRFS_WITH_PARENT) {
  96                 if (fh_len <  BTRFS_FID_SIZE_CONNECTABLE)
  97                         return NULL;
  98                 root_objectid = fid->root_objectid;
  99         } else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
 100                 if (fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
 101                         return NULL;
 102                 root_objectid = fid->parent_root_objectid;
 103         } else
 104                 return NULL;
 105
 106         objectid = fid->parent_objectid;
 107         generation = fid->parent_gen;
 108
 109         return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
 110 }
 111
 112 static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
 113                                          int fh_len, int fh_type)
 114 {
 115         struct btrfs_fid *fid = (struct btrfs_fid *) fh;
 116         u64 objectid, root_objectid;
 117         u32 generation;
 118
 119         if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
 120              fh_len < BTRFS_FID_SIZE_CONNECTABLE) &&
 121             (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
 122              fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
 123             (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
 124              fh_len < BTRFS_FID_SIZE_NON_CONNECTABLE))
 125                 return NULL;
 126
 127         objectid = fid->objectid;
 128         root_objectid = fid->root_objectid;
 129         generation = fid->gen;
 130
 131         return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
 132 }
 133
 134 struct dentry *btrfs_get_parent(struct dentry *child)
 135 {
 136         struct inode *dir = d_inode(child);
 137         struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 138         struct btrfs_root *root = BTRFS_I(dir)->root;
 139         struct btrfs_path *path;
 140         struct extent_buffer *leaf;
 141         struct btrfs_root_ref *ref;
 142         struct btrfs_key key;
 143         struct btrfs_key found_key;
 144         int ret;
 145
 146         path = btrfs_alloc_path();
 147         if (!path)
 148                 return ERR_PTR(-ENOMEM);
 149
 150         if (btrfs_ino(BTRFS_I(dir)) == BTRFS_FIRST_FREE_OBJECTID) {
 151                 key.objectid = root->root_key.objectid;
 152                 key.type = BTRFS_ROOT_BACKREF_KEY;
 153                 key.offset = (u64)-1;
 154                 root = fs_info->tree_root;
 155         } else {
 156                 key.objectid = btrfs_ino(BTRFS_I(dir));
 157                 key.type = BTRFS_INODE_REF_KEY;
 158                 key.offset = (u64)-1;
 159         }
 160
 161         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 162         if (ret < 0)
 163                 goto fail;
 164         if (ret == 0) {
 165                 /*
 166                  * Key with offset of -1 found, there would have to exist an
 167                  * inode with such number or a root with such id.
 168                  */
 169                 ret = -EUCLEAN;
 170                 goto fail;
 171         }
 172
 173         if (path->slots[0] == 0) {
 174                 ret = -ENOENT;
 175                 goto fail;
 176         }
 177
 178         path->slots[0]--;
 179         leaf = path->nodes[0];
 180
 181         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 182         if (found_key.objectid != key.objectid || found_key.type != key.type) {
 183                 ret = -ENOENT;
 184                 goto fail;
 185         }
 186
 187         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 188                 ref = btrfs_item_ptr(leaf, path->slots[0],
 189                                      struct btrfs_root_ref);
 190                 key.objectid = btrfs_root_ref_dirid(leaf, ref);
 191         } else {
 192                 key.objectid = found_key.offset;
 193         }
 194         btrfs_free_path(path);
 195
 196         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 197                 return btrfs_get_dentry(fs_info->sb, key.objectid,
 198                                         found_key.offset, 0, 0);
 199         }
 200
 201         return d_obtain_alias(btrfs_iget(fs_info->sb, key.objectid, root));
 202 fail:
 203         btrfs_free_path(path);
 204         return ERR_PTR(ret);
 205 }
 206
 207 static int btrfs_get_name(struct dentry *parent, char *name,
 208                           struct dentry *child)
 209 {
 210         struct inode *inode = d_inode(child);
 211         struct inode *dir = d_inode(parent);
 212         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 213         struct btrfs_path *path;
 214         struct btrfs_root *root = BTRFS_I(dir)->root;
 215         struct btrfs_inode_ref *iref;
 216         struct btrfs_root_ref *rref;
 217         struct extent_buffer *leaf;
 218         unsigned long name_ptr;
 219         struct btrfs_key key;
 220         int name_len;
 221         int ret;
 222         u64 ino;
 223
 224         if (!S_ISDIR(dir->i_mode))
 225                 return -EINVAL;
 226
 227         ino = btrfs_ino(BTRFS_I(inode));
 228
 229         path = btrfs_alloc_path();
 230         if (!path)
 231                 return -ENOMEM;
 232
 233         if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 234                 key.objectid = BTRFS_I(inode)->root->root_key.objectid;
 235                 key.type = BTRFS_ROOT_BACKREF_KEY;
 236                 key.offset = (u64)-1;
 237                 root = fs_info->tree_root;
 238         } else {
 239                 key.objectid = ino;
 240                 key.offset = btrfs_ino(BTRFS_I(dir));
 241                 key.type = BTRFS_INODE_REF_KEY;
 242         }
 243
 244         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 245         if (ret < 0) {
 246                 btrfs_free_path(path);
 247                 return ret;
 248         } else if (ret > 0) {
 249                 if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 250                         path->slots[0]--;
 251                 } else {
 252                         btrfs_free_path(path);
 253                         return -ENOENT;
 254                 }
 255         }
 256         leaf = path->nodes[0];
 257
 258         if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 259                 rref = btrfs_item_ptr(leaf, path->slots[0],
 260                                      struct btrfs_root_ref);
 261                 name_ptr = (unsigned long)(rref + 1);
 262                 name_len = btrfs_root_ref_name_len(leaf, rref);
 263         } else {
 264                 iref = btrfs_item_ptr(leaf, path->slots[0],
 265                                       struct btrfs_inode_ref);
 266                 name_ptr = (unsigned long)(iref + 1);
 267                 name_len = btrfs_inode_ref_name_len(leaf, iref);
 268         }
 269
 270         read_extent_buffer(leaf, name, name_ptr, name_len);
 271         btrfs_free_path(path);
 272
 273         /*
 274          * have to add the null termination to make sure that reconnect_path
 275          * gets the right len for strlen
 276          */
 277         name[name_len] = '\0';
 278
 279         return 0;
 280 }
 281
 282 const struct export_operations btrfs_export_ops = {
 283         .encode_fh      = btrfs_encode_fh,
 284         .fh_to_dentry   = btrfs_fh_to_dentry,
 285         .fh_to_parent   = btrfs_fh_to_parent,
 286         .get_parent     = btrfs_get_parent,
 287         .get_name       = btrfs_get_name,
 288 };