From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: [PATCH 0/2 v2] Fix fallout from changes to FUA and PREFLUSH definitions Date: Wed, 31 May 2017 09:44:31 +0200 Message-ID: <20170531074433.14298-1-jack@suse.cz> Return-path: Sender: linux-raid-owner@vger.kernel.org To: Shaohua Li Cc: Jan Kara , linux-raid@vger.kernel.org, Mike Snitzer , dm-devel@redhat.com List-Id: linux-raid.ids Hello, here are patches for DM/MD that address a possible performance issue caused by commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as synchronous". The core of the problem is that above mentioned commit removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...} definitions. generic_make_request_checks() however strips REQ_FUA and REQ_PREFLUSH flags from a bio when the storage doesn't report volatile write cache and thus write effectively becomes asynchronous which can lead to performance regressions. DM/MD guys, can you please have a look at patches and take them through your trees? Thanks! Honza