btrfs: remove extent_map::block_start member

The member extent_map::block_start can be calculated from
extent_map::disk_bytenr + extent_map::offset for regular extents.
And otherwise just extent_map::disk_bytenr.

And this is already validated by the validate_extent_map().  Now we can
remove the member.

However there is a special case in btrfs_create_dio_extent() where we
for NOCOW/PREALLOC ordered extents cannot directly use the resulting
btrfs_file_extent, as btrfs_split_ordered_extent() cannot handle them
yet.

So for that call site, we pass file_extent->disk_bytenr +
file_extent->num_bytes as disk_bytenr for the ordered extent, and 0 for
offset.

Reviewed-by: Johannes Thumshirn <[email protected]>
Reviewed-by: Filipe Manana <[email protected]>
Signed-off-by: Qu Wenruo <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index cd88432e7072..07b31d1c0926 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -507,7 +507,8 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 		 */
 		if (!em || cur < em->start ||
 		    (cur + fs_info->sectorsize > extent_map_end(em)) ||
-		    (em->block_start >> SECTOR_SHIFT) != orig_bio->bi_iter.bi_sector) {
+		    (extent_map_block_start(em) >> SECTOR_SHIFT) !=
+		    orig_bio->bi_iter.bi_sector) {
 			free_extent_map(em);
 			unlock_extent(tree, cur, page_end, NULL);
 			unlock_page(page);