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
  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
 165         BUG_ON(ret == 0); /* Key with offset of -1 found */
 166         if (path->slots[0] == 0) {
 167                 ret = -ENOENT;
 168                 goto fail;
 169         }
 170
 171         path->slots[0]--;
 172         leaf = path->nodes[0];
 173
 174         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 175         if (found_key.objectid != key.objectid || found_key.type != key.type) {
 176                 ret = -ENOENT;
 177                 goto fail;
 178         }
 179
 180         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 181                 ref = btrfs_item_ptr(leaf, path->slots[0],
 182                                      struct btrfs_root_ref);
 183                 key.objectid = btrfs_root_ref_dirid(leaf, ref);
 184         } else {
 185                 key.objectid = found_key.offset;
 186         }
 187         btrfs_free_path(path);
 188
 189         if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
 190                 return btrfs_get_dentry(fs_info->sb, key.objectid,
 191                                         found_key.offset, 0, 0);
 192         }
 193
 194         return d_obtain_alias(btrfs_iget(fs_info->sb, key.objectid, root));
 195 fail:
 196         btrfs_free_path(path);
 197         return ERR_PTR(ret);
 198 }
 199
 200 static int btrfs_get_name(struct dentry *parent, char *name,
 201                           struct dentry *child)
 202 {
 203         struct inode *inode = d_inode(child);
 204         struct inode *dir = d_inode(parent);
 205         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 206         struct btrfs_path *path;
 207         struct btrfs_root *root = BTRFS_I(dir)->root;
 208         struct btrfs_inode_ref *iref;
 209         struct btrfs_root_ref *rref;
 210         struct extent_buffer *leaf;
 211         unsigned long name_ptr;
 212         struct btrfs_key key;
 213         int name_len;
 214         int ret;
 215         u64 ino;
 216
 217         if (!S_ISDIR(dir->i_mode))
 218                 return -EINVAL;
 219
 220         ino = btrfs_ino(BTRFS_I(inode));
 221
 222         path = btrfs_alloc_path();
 223         if (!path)
 224                 return -ENOMEM;
 225
 226         if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 227                 key.objectid = BTRFS_I(inode)->root->root_key.objectid;
 228                 key.type = BTRFS_ROOT_BACKREF_KEY;
 229                 key.offset = (u64)-1;
 230                 root = fs_info->tree_root;
 231         } else {
 232                 key.objectid = ino;
 233                 key.offset = btrfs_ino(BTRFS_I(dir));
 234                 key.type = BTRFS_INODE_REF_KEY;
 235         }
 236
 237         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 238         if (ret < 0) {
 239                 btrfs_free_path(path);
 240                 return ret;
 241         } else if (ret > 0) {
 242                 if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 243                         path->slots[0]--;
 244                 } else {
 245                         btrfs_free_path(path);
 246                         return -ENOENT;
 247                 }
 248         }
 249         leaf = path->nodes[0];
 250
 251         if (ino == BTRFS_FIRST_FREE_OBJECTID) {
 252                 rref = btrfs_item_ptr(leaf, path->slots[0],
 253                                      struct btrfs_root_ref);
 254                 name_ptr = (unsigned long)(rref + 1);
 255                 name_len = btrfs_root_ref_name_len(leaf, rref);
 256         } else {
 257                 iref = btrfs_item_ptr(leaf, path->slots[0],
 258                                       struct btrfs_inode_ref);
 259                 name_ptr = (unsigned long)(iref + 1);
 260                 name_len = btrfs_inode_ref_name_len(leaf, iref);
 261         }
 262
 263         read_extent_buffer(leaf, name, name_ptr, name_len);
 264         btrfs_free_path(path);
 265
 266         /*
 267          * have to add the null termination to make sure that reconnect_path
 268          * gets the right len for strlen
 269          */
 270         name[name_len] = '\0';
 271
 272         return 0;
 273 }
 274
 275 const struct export_operations btrfs_export_ops = {
 276         .encode_fh      = btrfs_encode_fh,
 277         .fh_to_dentry   = btrfs_fh_to_dentry,
 278         .fh_to_parent   = btrfs_fh_to_parent,
 279         .get_parent     = btrfs_get_parent,
 280         .get_name       = btrfs_get_name,
 281 };