block: deprecate barrier and replace blk_queue_ordered() with blk_queue_flush()

Barrier is deemed too heavy and will soon be replaced by FLUSH/FUA
requests.  Deprecate barrier.  All REQ_HARDBARRIERs are failed with
-EOPNOTSUPP and blk_queue_ordered() is replaced with simpler
blk_queue_flush().

blk_queue_flush() takes combinations of REQ_FLUSH and FUA.  If a
device has write cache and can flush it, it should set REQ_FLUSH.  If
the device can handle FUA writes, it should also set REQ_FUA.

All blk_queue_ordered() users are converted.

* ORDERED_DRAIN is mapped to 0 which is the default value.
* ORDERED_DRAIN_FLUSH is mapped to REQ_FLUSH.
* ORDERED_DRAIN_FLUSH_FUA is mapped to REQ_FLUSH | REQ_FUA.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Boaz Harrosh <bharrosh@panasas.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Pierre Ossman <drzeus@drzeus.cx>
Cc: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index ee1a1e7e63cc..f06354183b29 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1203,11 +1203,13 @@ static int __make_request(struct request_queue *q, struct bio *bio)
         const unsigned int ff = bio->bi_rw & REQ_FAILFAST_MASK;
         int rw_flags;
 
-        if ((bio->bi_rw & REQ_HARDBARRIER) &&
-            (q->next_ordered == QUEUE_ORDERED_NONE)) {
+        /* REQ_HARDBARRIER is no more */
+        if (WARN_ONCE(bio->bi_rw & REQ_HARDBARRIER,
+                "block: HARDBARRIER is deprecated, use FLUSH/FUA instead\n")) {
                 bio_endio(bio, -EOPNOTSUPP);
                 return 0;
         }
+
         /*
          * low level driver can indicate that it wants pages above a
          * certain limit bounced to low memory (ie for highmem, or even