file.c

   1 /*
   2  * Copyright (C) 2014 Fujitsu.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <sys/stat.h>
  20 #include "ctree.h"
  21 #include "utils.h"
  22 #include "disk-io.h"
  23 #include "transaction.h"
  24 #include "kerncompat.h"
  25
  26 /*
  27  * Get the first file extent that covers (part of) the given range
  28  * Unlike kernel using extent_map to handle hole even no-hole is enabled,
  29  * progs don't have such infrastructure, so caller should do extra care
  30  * for no-hole.
  31  *
  32  * return 0 for found, and path points to the file extent.
  33  * return >0 for not found, and path points to the insert position.
  34  * return <0 for error.
  35  */
  36 int btrfs_get_extent(struct btrfs_trans_handle *trans,
  37                      struct btrfs_root *root,
  38                      struct btrfs_path *path,
  39                      u64 ino, u64 offset, u64 len, int ins_len)
  40 {
  41         struct btrfs_key key;
  42         struct btrfs_key found_key;
  43         struct btrfs_file_extent_item *fi_item;
  44         u64 end = 0;
  45         int ret = 0;
  46         int not_found = 1;
  47
  48         key.objectid = ino;
  49         key.type = BTRFS_EXTENT_DATA_KEY;
  50         key.offset = offset;
  51
  52         ret = btrfs_search_slot(trans, root, &key, path, ins_len,
  53                                 ins_len ? 1 : 0);
  54         if (ret <= 0)
  55                 goto out;
  56         if (ret > 0) {
  57                 /* Check previous file extent */
  58                 ret = btrfs_previous_item(root, path, ino,
  59                                           BTRFS_EXTENT_DATA_KEY);
  60                 if (ret < 0)
  61                         goto out;
  62                 if (ret > 0)
  63                         goto check_next;
  64         }
  65         btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
  66         if (found_key.objectid != ino ||
  67             found_key.type != BTRFS_EXTENT_DATA_KEY)
  68                 goto check_next;
  69
  70         fi_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  71                                  struct btrfs_file_extent_item);
  72         end = found_key.offset +
  73               btrfs_file_extent_ram_bytes(path->nodes[0], fi_item);
  74         /*
  75          * existing file extent
  76          * |--------|     |----|
  77          *      |-------|
  78          *      offset + len
  79          * OR
  80          * |---------------|
  81          *      |-------|
  82          */
  83         if (end > offset) {
  84                 not_found = 0;
  85                 goto out;
  86         }
  87 check_next:
  88         ret = btrfs_next_item(root, path);
  89         if (ret)
  90                 goto out;
  91
  92         btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
  93         if (found_key.objectid != ino ||
  94             found_key.type != BTRFS_EXTENT_DATA_KEY) {
  95                 ret = 1;
  96                 goto out;
  97         }
  98         if (found_key.offset < offset + len)
  99                 /*
 100                  * existing file extent
 101                  * |---|        |------|
 102                  *      |-------|
 103                  *      offset + len
 104                  */
 105                 not_found = 0;
 106         else
 107                 /*
 108                  * existing file extent
 109                  * |----|               |----|
 110                  *              |----|
 111                  *              offset + len
 112                  */
 113                 not_found = 1;
 114
 115         /*
 116          * To keep the search behavior consistent with search_slot(),
 117          * we need to go back to the prev leaf's nritem slot if
 118          * we are at the first slot of the leaf.
 119          */
 120         if (path->slots[0] == 0) {
 121                 ret = btrfs_prev_leaf(root, path);
 122                 /* Not possible */
 123                 if (ret)
 124                         goto out;
 125                 path->slots[0] = btrfs_header_nritems(path->nodes[0]);
 126         }
 127
 128 out:
 129         if (ret == 0)
 130                 ret = not_found;
 131         return ret;
 132 }
 133
 134 /*
 135  * Punch hole ranged [offset,len) for the file given by ino and root.
 136  *
 137  * Unlink kernel punch_hole, which will not zero/free existing extent,
 138  * instead it will return -EEXIST if there is any extents in the hole
 139  * range.
 140  */
 141 int btrfs_punch_hole(struct btrfs_trans_handle *trans,
 142                      struct btrfs_root *root,
 143                      u64 ino, u64 offset, u64 len)
 144 {
 145         struct btrfs_path *path;
 146         int ret = 0;
 147
 148         path = btrfs_alloc_path();
 149         if (!path)
 150                 return -ENOMEM;
 151
 152         ret = btrfs_get_extent(NULL, root, path, ino, offset, len, 0);
 153         if (ret < 0)
 154                 goto out;
 155         if (ret == 0) {
 156                 ret = -EEXIST;
 157                 goto out;
 158         }
 159
 160         ret = btrfs_insert_file_extent(trans, root, ino, offset, 0, 0, len);
 161 out:
 162         btrfs_free_path(path);
 163         return ret;
 164 }
 165
 166 /*
 167  * Read out content of one inode.
 168  *
 169  * @root:  fs/subvolume root containing the inode
 170  * @ino:   inode number
 171  * @start: offset inside the file, aligned to sectorsize
 172  * @len:   length to read, aligned to sectorisize
 173  * @dest:  where data will be stored
 174  *
 175  * NOTE:
 176  * 1) compression data is not supported yet
 177  * 2) @start and @len must be aligned to sectorsize
 178  * 3) data read out is also aligned to sectorsize, not truncated to inode size
 179  *
 180  * Return < 0 for fatal error during read.
 181  * Otherwise return the number of succesfully read data in bytes.
 182  */
 183 int btrfs_read_file(struct btrfs_root *root, u64 ino, u64 start, int len,
 184                     char *dest)
 185 {
 186         struct btrfs_fs_info *fs_info = root->fs_info;
 187         struct btrfs_key key;
 188         struct btrfs_path path;
 189         struct extent_buffer *leaf;
 190         struct btrfs_inode_item *ii;
 191         u64 isize;
 192         int no_holes = btrfs_fs_incompat(fs_info, NO_HOLES);
 193         int slot;
 194         int read = 0;
 195         int ret;
 196
 197         if (!IS_ALIGNED(start, fs_info->sectorsize) ||
 198             !IS_ALIGNED(len, fs_info->sectorsize)) {
 199                 warning("@start and @len must be aligned to %u for function %s",
 200                         fs_info->sectorsize, __func__);
 201                 return -EINVAL;
 202         }
 203
 204         btrfs_init_path(&path);
 205         key.objectid = ino;
 206         key.offset = start;
 207         key.type = BTRFS_EXTENT_DATA_KEY;
 208
 209         ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
 210         if (ret < 0)
 211                 goto out;
 212
 213         if (ret > 0) {
 214                 ret = btrfs_previous_item(root, &path, ino, BTRFS_EXTENT_DATA_KEY);
 215                 if (ret > 0) {
 216                         ret = -ENOENT;
 217                         goto out;
 218                 }
 219         }
 220
 221         /*
 222          * Reset @dest to all 0, so we don't need to care about holes in
 223          * no_hole mode, but focus on reading non-hole part.
 224          */
 225         memset(dest, 0, len);
 226         while (1) {
 227                 struct btrfs_file_extent_item *fi;
 228                 u64 extent_start;
 229                 u64 extent_len;
 230                 u64 read_start;
 231                 u64 read_len;
 232                 u64 read_len_ret;
 233                 u64 disk_bytenr;
 234
 235                 leaf = path.nodes[0];
 236                 slot = path.slots[0];
 237
 238                 btrfs_item_key_to_cpu(leaf, &key, slot);
 239                 if (key.objectid > ino)
 240                         break;
 241                 if (key.type != BTRFS_EXTENT_DATA_KEY || key.objectid != ino)
 242                         goto next;
 243
 244                 extent_start = key.offset;
 245                 if (extent_start >= start + len)
 246                         break;
 247
 248                 fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
 249                 if (btrfs_file_extent_compression(leaf, fi) !=
 250                     BTRFS_COMPRESS_NONE) {
 251                         ret = -ENOTTY;
 252                         break;
 253                 }
 254
 255                 /* Inline extent, one inode should only one inline extent */
 256                 if (btrfs_file_extent_type(leaf, fi) ==
 257                     BTRFS_FILE_EXTENT_INLINE) {
 258                         extent_len = btrfs_file_extent_ram_bytes(leaf, fi);
 259                         if (extent_start + extent_len <= start)
 260                                 goto next;
 261                         read_extent_buffer(leaf, dest,
 262                                 btrfs_file_extent_inline_start(fi), extent_len);
 263                         read += round_up(extent_len, fs_info->sectorsize);
 264                         break;
 265                 }
 266
 267                 extent_len = btrfs_file_extent_num_bytes(leaf, fi);
 268                 if (extent_start + extent_len <= start)
 269                         goto next;
 270
 271                 read_start = max(start, extent_start);
 272                 read_len = min(start + len, extent_start + extent_len) -
 273                            read_start;
 274
 275                 /* We have already zeroed @dest, nothing to do */
 276                 if (btrfs_file_extent_type(leaf, fi) ==
 277                     BTRFS_FILE_EXTENT_PREALLOC ||
 278                     btrfs_file_extent_disk_num_bytes(leaf, fi) == 0) {
 279                         read += read_len;
 280                         goto next;
 281                 }
 282
 283                 disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi) +
 284                               btrfs_file_extent_offset(leaf, fi);
 285                 read_len_ret = read_len;
 286                 ret = read_extent_data(fs_info, dest + read_start - start, disk_bytenr,
 287                                        &read_len_ret, 0);
 288                 if (ret < 0)
 289                         break;
 290                 /* Short read, something went wrong */
 291                 if (read_len_ret != read_len)
 292                         return -EIO;
 293                 read += read_len;
 294 next:
 295                 ret = btrfs_next_item(root, &path);
 296                 if (ret > 0) {
 297                         ret = 0;
 298                         break;
 299                 }
 300         }
 301
 302         /*
 303          * Special trick for no_holes, since for no_holes we don't have good
 304          * method to account skipped and tailling holes, we used
 305          * min(inode size, len) as return value
 306          */
 307         if (no_holes) {
 308                 btrfs_release_path(&path);
 309                 key.objectid = ino;
 310                 key.offset = 0;
 311                 key.type = BTRFS_INODE_ITEM_KEY;
 312                 ret = btrfs_lookup_inode(NULL, root, &path, &key, 0);
 313                 if (ret < 0)
 314                         goto out;
 315                 if (ret > 0) {
 316                         ret = -ENOENT;
 317                         goto out;
 318                 }
 319                 ii = btrfs_item_ptr(path.nodes[0], path.slots[0],
 320                                     struct btrfs_inode_item);
 321                 isize = round_up(btrfs_inode_size(path.nodes[0], ii),
 322                                  fs_info->sectorsize);
 323                 read = min_t(u64, isize - start, len);
 324         }
 325 out:
 326         btrfs_release_path(&path);
 327         if (!ret)
 328                 ret = read;
 329         return ret;
 330 }