On Wed, May 31 2017 at 3:44am -0400,
Jan Kara <jack@xxxxxxx> wrote:
> Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
> synchronous" 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
>
> Fix the problem by making sure all bios which are synchronous are
> properly marked with REQ_SYNC.
>
> CC: Mike Snitzer <snitzer@xxxxxxxxxx>
> CC: dm-devel@xxxxxxxxxx
> Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
> CC: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jan Kara <jack@xxxxxxx>
thanks, staged for 4.12-rc4
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