Commit 04d4ba4c authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: make check_compressed_csum() to be subpage compatible 



Currently check_compressed_csum() completely relies on sectorsize ==
PAGE_SIZE to do checksum verification for compressed extents.

To make it subpage compatible, this patch will:
- Do extra calculation for the csum range
  Since we have multiple sectors inside a page, we need to only hash
  the range we want, not the full page anymore.

- Do sector-by-sector hash inside the page

With this patch and previous conversion on
btrfs_submit_compressed_read(), now we can read subpage compressed
extents properly, and do proper csum verification.

Reviewed-by: default avatarAnand Jain <anand.jain@oracle.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent be6a1361

fs/btrfs/compression.c

+26 −13
Original line number Diff line number Diff line
@@ -141,6 +141,7 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio, 
	struct btrfs_fs_info *fs_info = inode->root->fs_info;

	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);

	const u32 csum_size = fs_info->csum_size;

	const u32 sectorsize = fs_info->sectorsize;

	struct page *page;

	unsigned long i;

	char *kaddr;
@@ -154,13 +155,23 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio, 
	shash->tfm = fs_info->csum_shash;



	for (i = 0; i < cb->nr_pages; i++) {

		u32 pg_offset;

		u32 bytes_left = PAGE_SIZE;

		page = cb->compressed_pages[i];



		/* Determine the remaining bytes inside the page first */

		if (i == cb->nr_pages - 1)

			bytes_left = cb->compressed_len - i * PAGE_SIZE;



		/* Hash through the page sector by sector */

		for (pg_offset = 0; pg_offset < bytes_left;

		     pg_offset += sectorsize) {

			kaddr = kmap_atomic(page);

		crypto_shash_digest(shash, kaddr, PAGE_SIZE, csum);

			crypto_shash_digest(shash, kaddr + pg_offset,

					    sectorsize, csum);

			kunmap_atomic(kaddr);



		if (memcmp(&csum, cb_sum, csum_size)) {

			if (memcmp(&csum, cb_sum, csum_size) != 0) {

				btrfs_print_data_csum_error(inode, disk_start,

						csum, cb_sum, cb->mirror_num);

				if (btrfs_io_bio(bio)->device)
@@ -170,6 +181,8 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio, 
				return -EIO;

			}

			cb_sum += csum_size;

			disk_start += sectorsize;

		}

	}

	return 0;

}