From 5cb8850c9c4a7605f74f5c9c7ecadd0b02e87a25 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kmo@daterainc.com>
Date: Fri, 7 Feb 2014 13:53:46 -0700
Subject: [PATCH] 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>
---
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