Commit 949b3273 authored by Goldwyn Rodrigues's avatar Goldwyn Rodrigues Committed by David Sterba
Browse files

btrfs: use iosize while reading compressed pages 



While using compression, a submitted bio is mapped with a compressed bio
which performs the read from disk, decompresses and returns uncompressed
data to original bio. The original bio must reflect the uncompressed
size (iosize) of the I/O to be performed, or else the page just gets the
decompressed I/O length of data (disk_io_size). The compressed bio
checks the extent map and gets the correct length while performing the
I/O from disk.

This came up in subpage work when only compressed length of the original
bio was filled in the page. This worked correctly for pagesize ==
sectorsize because both compressed and uncompressed data are at pagesize
boundaries, and would end up filling the requested page.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent eefa45f5

fs/btrfs/extent_io.c

+3 −7
Original line number Diff line number Diff line
@@ -3158,7 +3158,6 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, 
	int nr = 0;

	size_t pg_offset = 0;

	size_t iosize;

	size_t disk_io_size;

	size_t blocksize = inode->i_sb->s_blocksize;

	unsigned long this_bio_flag = 0;

	struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
@@ -3224,13 +3223,10 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, 
		iosize = min(extent_map_end(em) - cur, end - cur + 1);

		cur_end = min(extent_map_end(em) - 1, end);

		iosize = ALIGN(iosize, blocksize);

		if (this_bio_flag & EXTENT_BIO_COMPRESSED) {

			disk_io_size = em->block_len;

		if (this_bio_flag & EXTENT_BIO_COMPRESSED)

			offset = em->block_start;

		} else {

		else

			offset = em->block_start + extent_offset;

			disk_io_size = iosize;

		}

		block_start = em->block_start;

		if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))

			block_start = EXTENT_MAP_HOLE;
@@ -3319,7 +3315,7 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, 
		}



		ret = submit_extent_page(REQ_OP_READ | read_flags, NULL,

					 page, offset, disk_io_size,

					 page, offset, iosize,

					 pg_offset, bio,

					 end_bio_extent_readpage, 0,

					 *bio_flags,