From: Joe Thornber <ejt@redhat.com>
Date: Thu, 31 Oct 2013 17:55:48 +0000 (-0400)
Subject: dm cache: promotion optimisation for writes
X-Git-Tag: v3.13-rc1~97^2~7
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c9d28d5d09a0fd5f02f1321c8e18ff7d9f92270b;p=pandora-kernel.git

dm cache: promotion optimisation for writes

If a write block triggers promotion and covers a whole block we can
avoid a copy.

Introduce dm_{hook,unhook}_bio to simplify saving and restoring bio
fields (bi_private is now used by overwrite).  Switch writethrough
support over to using these helpers too.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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