block: filter flush bio's in __generic_make_request()

There are a number of make_request based drivers which don't support
cache flushes.  Filter out flush bio's in __generic_make_request() so
that they don't have to worry about them.  All FLUSH/FUA requests with
data are converted to regular IO requests and empty ones are completed
immediately.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 18455c4f618a..495bdc4a23da 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1509,6 +1509,19 @@ static inline void __generic_make_request(struct bio *bio)
                 if (bio_check_eod(bio, nr_sectors))
                         goto end_io;
 
+                /*
+                 * Filter flush bio's early so that make_request based
+                 * drivers without flush support don't have to worry
+                 * about them.
+                 */
+                if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
+                        bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
+                        if (!nr_sectors) {
+                                err = 0;
+                                goto end_io;
+                        }
+                }
+
                 if ((bio->bi_rw & REQ_DISCARD) &&
                     (!blk_queue_discard(q) ||
                      ((bio->bi_rw & REQ_SECURE) &&