On Tue, May 02, 2017 at 05:03:50PM +0200, Jan Kara 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: David Sterba <dsterba@xxxxxxxx>
> CC: linux-btrfs@xxxxxxxxxxxxxxx
> Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
> Signed-off-by: Jan Kara <jack@xxxxxxx>
Acked-by: David Sterba <dsterba@xxxxxxxx>
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