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-rw-r--r--fs/squashfs/block.c359
1 files changed, 359 insertions, 0 deletions
diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
new file mode 100644
index 0000000000..581ce95193
--- /dev/null
+++ b/fs/squashfs/block.c
@@ -0,0 +1,359 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ *
+ * block.c
+ */
+
+/*
+ * This file implements the low-level routines to read and decompress
+ * datablocks and metadata blocks.
+ */
+
+#include <linux/blkdev.h>
+#include <linux/fs.h>
+#include <linux/vfs.h>
+#include <linux/slab.h>
+#include <linux/pagemap.h>
+#include <linux/string.h>
+#include <linux/bio.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+#include "page_actor.h"
+
+/*
+ * Returns the amount of bytes copied to the page actor.
+ */
+static int copy_bio_to_actor(struct bio *bio,
+ struct squashfs_page_actor *actor,
+ int offset, int req_length)
+{
+ void *actor_addr;
+ struct bvec_iter_all iter_all = {};
+ struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
+ int copied_bytes = 0;
+ int actor_offset = 0;
+
+ squashfs_actor_nobuff(actor);
+ actor_addr = squashfs_first_page(actor);
+
+ if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
+ return 0;
+
+ while (copied_bytes < req_length) {
+ int bytes_to_copy = min_t(int, bvec->bv_len - offset,
+ PAGE_SIZE - actor_offset);
+
+ bytes_to_copy = min_t(int, bytes_to_copy,
+ req_length - copied_bytes);
+ if (!IS_ERR(actor_addr))
+ memcpy(actor_addr + actor_offset, bvec_virt(bvec) +
+ offset, bytes_to_copy);
+
+ actor_offset += bytes_to_copy;
+ copied_bytes += bytes_to_copy;
+ offset += bytes_to_copy;
+
+ if (actor_offset >= PAGE_SIZE) {
+ actor_addr = squashfs_next_page(actor);
+ if (!actor_addr)
+ break;
+ actor_offset = 0;
+ }
+ if (offset >= bvec->bv_len) {
+ if (!bio_next_segment(bio, &iter_all))
+ break;
+ offset = 0;
+ }
+ }
+ squashfs_finish_page(actor);
+ return copied_bytes;
+}
+
+static int squashfs_bio_read_cached(struct bio *fullbio,
+ struct address_space *cache_mapping, u64 index, int length,
+ u64 read_start, u64 read_end, int page_count)
+{
+ struct page *head_to_cache = NULL, *tail_to_cache = NULL;
+ struct block_device *bdev = fullbio->bi_bdev;
+ int start_idx = 0, end_idx = 0;
+ struct bvec_iter_all iter_all;
+ struct bio *bio = NULL;
+ struct bio_vec *bv;
+ int idx = 0;
+ int err = 0;
+
+ bio_for_each_segment_all(bv, fullbio, iter_all) {
+ struct page *page = bv->bv_page;
+
+ if (page->mapping == cache_mapping) {
+ idx++;
+ continue;
+ }
+
+ /*
+ * We only use this when the device block size is the same as
+ * the page size, so read_start and read_end cover full pages.
+ *
+ * Compare these to the original required index and length to
+ * only cache pages which were requested partially, since these
+ * are the ones which are likely to be needed when reading
+ * adjacent blocks.
+ */
+ if (idx == 0 && index != read_start)
+ head_to_cache = page;
+ else if (idx == page_count - 1 && index + length != read_end)
+ tail_to_cache = page;
+
+ if (!bio || idx != end_idx) {
+ struct bio *new = bio_alloc_clone(bdev, fullbio,
+ GFP_NOIO, &fs_bio_set);
+
+ if (bio) {
+ bio_trim(bio, start_idx * PAGE_SECTORS,
+ (end_idx - start_idx) * PAGE_SECTORS);
+ bio_chain(bio, new);
+ submit_bio(bio);
+ }
+
+ bio = new;
+ start_idx = idx;
+ }
+
+ idx++;
+ end_idx = idx;
+ }
+
+ if (bio) {
+ bio_trim(bio, start_idx * PAGE_SECTORS,
+ (end_idx - start_idx) * PAGE_SECTORS);
+ err = submit_bio_wait(bio);
+ bio_put(bio);
+ }
+
+ if (err)
+ return err;
+
+ if (head_to_cache) {
+ int ret = add_to_page_cache_lru(head_to_cache, cache_mapping,
+ read_start >> PAGE_SHIFT,
+ GFP_NOIO);
+
+ if (!ret) {
+ SetPageUptodate(head_to_cache);
+ unlock_page(head_to_cache);
+ }
+
+ }
+
+ if (tail_to_cache) {
+ int ret = add_to_page_cache_lru(tail_to_cache, cache_mapping,
+ (read_end >> PAGE_SHIFT) - 1,
+ GFP_NOIO);
+
+ if (!ret) {
+ SetPageUptodate(tail_to_cache);
+ unlock_page(tail_to_cache);
+ }
+ }
+
+ return 0;
+}
+
+static struct page *squashfs_get_cache_page(struct address_space *mapping,
+ pgoff_t index)
+{
+ struct page *page;
+
+ if (!mapping)
+ return NULL;
+
+ page = find_get_page(mapping, index);
+ if (!page)
+ return NULL;
+
+ if (!PageUptodate(page)) {
+ put_page(page);
+ return NULL;
+ }
+
+ return page;
+}
+
+static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
+ struct bio **biop, int *block_offset)
+{
+ struct squashfs_sb_info *msblk = sb->s_fs_info;
+ struct address_space *cache_mapping = msblk->cache_mapping;
+ const u64 read_start = round_down(index, msblk->devblksize);
+ const sector_t block = read_start >> msblk->devblksize_log2;
+ const u64 read_end = round_up(index + length, msblk->devblksize);
+ const sector_t block_end = read_end >> msblk->devblksize_log2;
+ int offset = read_start - round_down(index, PAGE_SIZE);
+ int total_len = (block_end - block) << msblk->devblksize_log2;
+ const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
+ int error, i;
+ struct bio *bio;
+
+ bio = bio_kmalloc(page_count, GFP_NOIO);
+ if (!bio)
+ return -ENOMEM;
+ bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);
+ bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
+
+ for (i = 0; i < page_count; ++i) {
+ unsigned int len =
+ min_t(unsigned int, PAGE_SIZE - offset, total_len);
+ pgoff_t index = (read_start >> PAGE_SHIFT) + i;
+ struct page *page;
+
+ page = squashfs_get_cache_page(cache_mapping, index);
+ if (!page)
+ page = alloc_page(GFP_NOIO);
+
+ if (!page) {
+ error = -ENOMEM;
+ goto out_free_bio;
+ }
+
+ /*
+ * Use the __ version to avoid merging since we need each page
+ * to be separate when we check for and avoid cached pages.
+ */
+ __bio_add_page(bio, page, len, offset);
+ offset = 0;
+ total_len -= len;
+ }
+
+ if (cache_mapping)
+ error = squashfs_bio_read_cached(bio, cache_mapping, index,
+ length, read_start, read_end,
+ page_count);
+ else
+ error = submit_bio_wait(bio);
+ if (error)
+ goto out_free_bio;
+
+ *biop = bio;
+ *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
+ return 0;
+
+out_free_bio:
+ bio_free_pages(bio);
+ bio_uninit(bio);
+ kfree(bio);
+ return error;
+}
+
+/*
+ * Read and decompress a metadata block or datablock. Length is non-zero
+ * if a datablock is being read (the size is stored elsewhere in the
+ * filesystem), otherwise the length is obtained from the first two bytes of
+ * the metadata block. A bit in the length field indicates if the block
+ * is stored uncompressed in the filesystem (usually because compression
+ * generated a larger block - this does occasionally happen with compression
+ * algorithms).
+ */
+int squashfs_read_data(struct super_block *sb, u64 index, int length,
+ u64 *next_index, struct squashfs_page_actor *output)
+{
+ struct squashfs_sb_info *msblk = sb->s_fs_info;
+ struct bio *bio = NULL;
+ int compressed;
+ int res;
+ int offset;
+
+ if (length) {
+ /*
+ * Datablock.
+ */
+ compressed = SQUASHFS_COMPRESSED_BLOCK(length);
+ length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
+ TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
+ index, compressed ? "" : "un", length, output->length);
+ } else {
+ /*
+ * Metadata block.
+ */
+ const u8 *data;
+ struct bvec_iter_all iter_all = {};
+ struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
+
+ if (index + 2 > msblk->bytes_used) {
+ res = -EIO;
+ goto out;
+ }
+ res = squashfs_bio_read(sb, index, 2, &bio, &offset);
+ if (res)
+ goto out;
+
+ if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
+ res = -EIO;
+ goto out_free_bio;
+ }
+ /* Extract the length of the metadata block */
+ data = bvec_virt(bvec);
+ length = data[offset];
+ if (offset < bvec->bv_len - 1) {
+ length |= data[offset + 1] << 8;
+ } else {
+ if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
+ res = -EIO;
+ goto out_free_bio;
+ }
+ data = bvec_virt(bvec);
+ length |= data[0] << 8;
+ }
+ bio_free_pages(bio);
+ bio_uninit(bio);
+ kfree(bio);
+
+ compressed = SQUASHFS_COMPRESSED(length);
+ length = SQUASHFS_COMPRESSED_SIZE(length);
+ index += 2;
+
+ TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
+ compressed ? "" : "un", length);
+ }
+ if (length < 0 || length > output->length ||
+ (index + length) > msblk->bytes_used) {
+ res = -EIO;
+ goto out;
+ }
+
+ if (next_index)
+ *next_index = index + length;
+
+ res = squashfs_bio_read(sb, index, length, &bio, &offset);
+ if (res)
+ goto out;
+
+ if (compressed) {
+ if (!msblk->stream) {
+ res = -EIO;
+ goto out_free_bio;
+ }
+ res = msblk->thread_ops->decompress(msblk, bio, offset, length, output);
+ } else {
+ res = copy_bio_to_actor(bio, output, offset, length);
+ }
+
+out_free_bio:
+ bio_free_pages(bio);
+ bio_uninit(bio);
+ kfree(bio);
+out:
+ if (res < 0) {
+ ERROR("Failed to read block 0x%llx: %d\n", index, res);
+ if (msblk->panic_on_errors)
+ panic("squashfs read failed");
+ }
+
+ return res;
+}
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