Allow elevators to sort/merge discard requests

But blkdev_issue_discard() still emits requests which are interpreted as
soft barriers, because naïve callers might otherwise issue subsequent
writes to those same sectors, which might cross on the queue (if they're
reallocated quickly enough).

Callers still _can_ issue non-barrier discard requests, but they have to
take care of queue ordering for themselves.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 1fdfc5621c83..33c3947d61e9 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -188,8 +188,8 @@ struct bio {
 #define bio_failfast(bio)       ((bio)->bi_rw & (1 << BIO_RW_FAILFAST))
 #define bio_rw_ahead(bio)       ((bio)->bi_rw & (1 << BIO_RW_AHEAD))
 #define bio_rw_meta(bio)        ((bio)->bi_rw & (1 << BIO_RW_META))
-#define bio_empty_barrier(bio)  (bio_barrier(bio) && !bio_has_data(bio))
 #define bio_discard(bio)        ((bio)->bi_rw & (1 << BIO_RW_DISCARD))
+#define bio_empty_barrier(bio)  (bio_barrier(bio) && !bio_has_data(bio) && !bio_discard(bio))
 
 static inline unsigned int bio_cur_sectors(struct bio *bio)
 {