fs/squashfs/block.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Squashfs - a compressed read only filesystem for Linux
   4  *
   5  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   6  * Phillip Lougher <phillip@squashfs.org.uk>
   7  *
   8  * block.c
   9  */
  10
  11 /*
  12  * This file implements the low-level routines to read and decompress
  13  * datablocks and metadata blocks.
  14  */
  15
  16 #include <linux/blkdev.h>
  17 #include <linux/fs.h>
  18 #include <linux/vfs.h>
  19 #include <linux/slab.h>
  20 #include <linux/string.h>
  21 #include <linux/buffer_head.h>
  22 #include <linux/bio.h>
  23
  24 #include "squashfs_fs.h"
  25 #include "squashfs_fs_sb.h"
  26 #include "squashfs.h"
  27 #include "decompressor.h"
  28 #include "page_actor.h"
  29
  30 /*
  31  * Returns the amount of bytes copied to the page actor.
  32  */
  33 static int copy_bio_to_actor(struct bio *bio,
  34                              struct squashfs_page_actor *actor,
  35                              int offset, int req_length)
  36 {
  37         void *actor_addr = squashfs_first_page(actor);
  38         struct bvec_iter_all iter_all = {};
  39         struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
  40         int copied_bytes = 0;
  41         int actor_offset = 0;
  42
  43         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
  44                 return 0;
  45
  46         while (copied_bytes < req_length) {
  47                 int bytes_to_copy = min_t(int, bvec->bv_len - offset,
  48                                           PAGE_SIZE - actor_offset);
  49
  50                 bytes_to_copy = min_t(int, bytes_to_copy,
  51                                       req_length - copied_bytes);
  52                 memcpy(actor_addr + actor_offset,
  53                        page_address(bvec->bv_page) + bvec->bv_offset + offset,
  54                        bytes_to_copy);
  55
  56                 actor_offset += bytes_to_copy;
  57                 copied_bytes += bytes_to_copy;
  58                 offset += bytes_to_copy;
  59
  60                 if (actor_offset >= PAGE_SIZE) {
  61                         actor_addr = squashfs_next_page(actor);
  62                         if (!actor_addr)
  63                                 break;
  64                         actor_offset = 0;
  65                 }
  66                 if (offset >= bvec->bv_len) {
  67                         if (!bio_next_segment(bio, &iter_all))
  68                                 break;
  69                         offset = 0;
  70                 }
  71         }
  72         squashfs_finish_page(actor);
  73         return copied_bytes;
  74 }
  75
  76 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
  77                              struct bio **biop, int *block_offset)
  78 {
  79         struct squashfs_sb_info *msblk = sb->s_fs_info;
  80         const u64 read_start = round_down(index, msblk->devblksize);
  81         const sector_t block = read_start >> msblk->devblksize_log2;
  82         const u64 read_end = round_up(index + length, msblk->devblksize);
  83         const sector_t block_end = read_end >> msblk->devblksize_log2;
  84         int offset = read_start - round_down(index, PAGE_SIZE);
  85         int total_len = (block_end - block) << msblk->devblksize_log2;
  86         const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
  87         int error, i;
  88         struct bio *bio;
  89
  90         bio = bio_alloc(GFP_NOIO, page_count);
  91         if (!bio)
  92                 return -ENOMEM;
  93
  94         bio_set_dev(bio, sb->s_bdev);
  95         bio->bi_opf = READ;
  96         bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
  97
  98         for (i = 0; i < page_count; ++i) {
  99                 unsigned int len =
 100                         min_t(unsigned int, PAGE_SIZE - offset, total_len);
 101                 struct page *page = alloc_page(GFP_NOIO);
 102
 103                 if (!page) {
 104                         error = -ENOMEM;
 105                         goto out_free_bio;
 106                 }
 107                 if (!bio_add_page(bio, page, len, offset)) {
 108                         error = -EIO;
 109                         goto out_free_bio;
 110                 }
 111                 offset = 0;
 112                 total_len -= len;
 113         }
 114
 115         error = submit_bio_wait(bio);
 116         if (error)
 117                 goto out_free_bio;
 118
 119         *biop = bio;
 120         *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
 121         return 0;
 122
 123 out_free_bio:
 124         bio_free_pages(bio);
 125         bio_put(bio);
 126         return error;
 127 }
 128
 129 /*
 130  * Read and decompress a metadata block or datablock.  Length is non-zero
 131  * if a datablock is being read (the size is stored elsewhere in the
 132  * filesystem), otherwise the length is obtained from the first two bytes of
 133  * the metadata block.  A bit in the length field indicates if the block
 134  * is stored uncompressed in the filesystem (usually because compression
 135  * generated a larger block - this does occasionally happen with compression
 136  * algorithms).
 137  */
 138 int squashfs_read_data(struct super_block *sb, u64 index, int length,
 139                        u64 *next_index, struct squashfs_page_actor *output)
 140 {
 141         struct squashfs_sb_info *msblk = sb->s_fs_info;
 142         struct bio *bio = NULL;
 143         int compressed;
 144         int res;
 145         int offset;
 146
 147         if (length) {
 148                 /*
 149                  * Datablock.
 150                  */
 151                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
 152                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
 153                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
 154                         index, compressed ? "" : "un", length, output->length);
 155         } else {
 156                 /*
 157                  * Metadata block.
 158                  */
 159                 const u8 *data;
 160                 struct bvec_iter_all iter_all = {};
 161                 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
 162
 163                 if (index + 2 > msblk->bytes_used) {
 164                         res = -EIO;
 165                         goto out;
 166                 }
 167                 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
 168                 if (res)
 169                         goto out;
 170
 171                 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 172                         res = -EIO;
 173                         goto out_free_bio;
 174                 }
 175                 /* Extract the length of the metadata block */
 176                 data = page_address(bvec->bv_page) + bvec->bv_offset;
 177                 length = data[offset];
 178                 if (offset <= bvec->bv_len - 1) {
 179                         length |= data[offset + 1] << 8;
 180                 } else {
 181                         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 182                                 res = -EIO;
 183                                 goto out_free_bio;
 184                         }
 185                         data = page_address(bvec->bv_page) + bvec->bv_offset;
 186                         length |= data[0] << 8;
 187                 }
 188                 bio_free_pages(bio);
 189                 bio_put(bio);
 190
 191                 compressed = SQUASHFS_COMPRESSED(length);
 192                 length = SQUASHFS_COMPRESSED_SIZE(length);
 193                 index += 2;
 194
 195                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
 196                       compressed ? "" : "un", length);
 197         }
 198         if (next_index)
 199                 *next_index = index + length;
 200
 201         res = squashfs_bio_read(sb, index, length, &bio, &offset);
 202         if (res)
 203                 goto out;
 204
 205         if (compressed) {
 206                 if (!msblk->stream) {
 207                         res = -EIO;
 208                         goto out_free_bio;
 209                 }
 210                 res = squashfs_decompress(msblk, bio, offset, length, output);
 211         } else {
 212                 res = copy_bio_to_actor(bio, output, offset, length);
 213         }
 214
 215 out_free_bio:
 216         bio_free_pages(bio);
 217         bio_put(bio);
 218 out:
 219         if (res < 0)
 220                 ERROR("Failed to read block 0x%llx: %d\n", index, res);
 221
 222         return res;
 223 }