btrfs: submit a writeback bio per extent_buffer
Stop trying to cluster writes of multiple extent_buffers into a single
bio. There is no need for that as the blk_plug mechanism used all the
way up in writeback_inodes_wb gives us the same I/O pattern even with
multiple bios. Removing the clustering simplifies
lock_extent_buffer_for_io a lot and will also allow passing the eb
as private data to the end I/O handler.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>