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 <johannes.thumshirn@wdc.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 10 insertions, 12 deletions

diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 5312bb542af0..2bcf7149b44c 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -91,18 +91,6 @@ struct extent_map {
 	u64 ram_bytes;
 
 	/*
-	 * The on-disk logical bytenr for the file extent.
-	 *
-	 * For compressed extents it matches btrfs_file_extent_item::disk_bytenr.
-	 * For uncompressed extents it matches
-	 * btrfs_file_extent_item::disk_bytenr + btrfs_file_extent_item::offset
-	 *
-	 * For holes it is EXTENT_MAP_HOLE and for inline extents it is
-	 * EXTENT_MAP_INLINE.
-	 */
-	u64 block_start;
-
-	/*
 	 * Generation of the extent map, for merged em it's the highest
 	 * generation of all merged ems.
 	 * For non-merged extents, it's from btrfs_file_extent_item::generation.
@@ -162,6 +150,16 @@ static inline int extent_map_in_tree(const struct extent_map *em)
 	return !RB_EMPTY_NODE(&em->rb_node);
 }
 
+static inline u64 extent_map_block_start(const struct extent_map *em)
+{
+	if (em->disk_bytenr < EXTENT_MAP_LAST_BYTE) {
+		if (extent_map_is_compressed(em))
+			return em->disk_bytenr;
+		return em->disk_bytenr + em->offset;
+	}
+	return em->disk_bytenr;
+}
+
 static inline u64 extent_map_end(const struct extent_map *em)
 {
 	if (em->start + em->len < em->start)