tree 401b42c4f5898a54c11c36da7ac37a14479bfffe
parent 087787959ce851d7bbb19f10f6e9241b7f85a3ca
author Kent Overstreet <kmo@daterainc.com> 1391806426 -0700
committer Jens Axboe <axboe@fb.com> 1391806448 -0700

block: Explicitly handle discard/write same segments

Immutable biovecs changed the way biovecs are interpreted - drivers no
longer use bi_vcnt, they have to go by bi_iter.bi_size (to allow for
using part of an existing segment without modifying it).

This breaks with discards and write_same bios, since for those bi_size
has nothing to do with segments in the biovec. So for now, we need a
fairly gross hack - we fortunately know that there will never be more
than one segment for the entire request, so we can special case
discard/write_same.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>