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         if (page_count <= BIO_MAX_PAGES)
  91                 bio = bio_alloc(GFP_NOIO, page_count);
  92         else
  93                 bio = bio_kmalloc(GFP_NOIO, page_count);
  94
  95         if (!bio)
  96                 return -ENOMEM;
  97
  98         bio_set_dev(bio, sb->s_bdev);
  99         bio->bi_opf = READ;
 100         bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
 101
 102         for (i = 0; i < page_count; ++i) {
 103                 unsigned int len =
 104                         min_t(unsigned int, PAGE_SIZE - offset, total_len);
 105                 struct page *page = alloc_page(GFP_NOIO);
 106
 107                 if (!page) {
 108                         error = -ENOMEM;
 109                         goto out_free_bio;
 110                 }
 111                 if (!bio_add_page(bio, page, len, offset)) {
 112                         error = -EIO;
 113                         goto out_free_bio;
 114                 }
 115                 offset = 0;
 116                 total_len -= len;
 117         }
 118
 119         error = submit_bio_wait(bio);
 120         if (error)
 121                 goto out_free_bio;
 122
 123         *biop = bio;
 124         *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
 125         return 0;
 126
 127 out_free_bio:
 128         bio_free_pages(bio);
 129         bio_put(bio);
 130         return error;
 131 }
 132
 133 /*
 134  * Read and decompress a metadata block or datablock.  Length is non-zero
 135  * if a datablock is being read (the size is stored elsewhere in the
 136  * filesystem), otherwise the length is obtained from the first two bytes of
 137  * the metadata block.  A bit in the length field indicates if the block
 138  * is stored uncompressed in the filesystem (usually because compression
 139  * generated a larger block - this does occasionally happen with compression
 140  * algorithms).
 141  */
 142 int squashfs_read_data(struct super_block *sb, u64 index, int length,
 143                        u64 *next_index, struct squashfs_page_actor *output)
 144 {
 145         struct squashfs_sb_info *msblk = sb->s_fs_info;
 146         struct bio *bio = NULL;
 147         int compressed;
 148         int res;
 149         int offset;
 150
 151         if (length) {
 152                 /*
 153                  * Datablock.
 154                  */
 155                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
 156                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
 157                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
 158                         index, compressed ? "" : "un", length, output->length);
 159         } else {
 160                 /*
 161                  * Metadata block.
 162                  */
 163                 const u8 *data;
 164                 struct bvec_iter_all iter_all = {};
 165                 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
 166
 167                 if (index + 2 > msblk->bytes_used) {
 168                         res = -EIO;
 169                         goto out;
 170                 }
 171                 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
 172                 if (res)
 173                         goto out;
 174
 175                 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 176                         res = -EIO;
 177                         goto out_free_bio;
 178                 }
 179                 /* Extract the length of the metadata block */
 180                 data = page_address(bvec->bv_page) + bvec->bv_offset;
 181                 length = data[offset];
 182                 if (offset < bvec->bv_len - 1) {
 183                         length |= data[offset + 1] << 8;
 184                 } else {
 185                         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 186                                 res = -EIO;
 187                                 goto out_free_bio;
 188                         }
 189                         data = page_address(bvec->bv_page) + bvec->bv_offset;
 190                         length |= data[0] << 8;
 191                 }
 192                 bio_free_pages(bio);
 193                 bio_put(bio);
 194
 195                 compressed = SQUASHFS_COMPRESSED(length);
 196                 length = SQUASHFS_COMPRESSED_SIZE(length);
 197                 index += 2;
 198
 199                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
 200                       compressed ? "" : "un", length);
 201         }
 202         if (next_index)
 203                 *next_index = index + length;
 204
 205         res = squashfs_bio_read(sb, index, length, &bio, &offset);
 206         if (res)
 207                 goto out;
 208
 209         if (compressed) {
 210                 if (!msblk->stream) {
 211                         res = -EIO;
 212                         goto out_free_bio;
 213                 }
 214                 res = squashfs_decompress(msblk, bio, offset, length, output);
 215         } else {
 216                 res = copy_bio_to_actor(bio, output, offset, length);
 217         }
 218
 219 out_free_bio:
 220         bio_free_pages(bio);
 221         bio_put(bio);
 222 out:
 223         if (res < 0)
 224                 ERROR("Failed to read block 0x%llx: %d\n", index, res);
 225
 226         return res;
 227 }