SCSI-ml needs a way to mark a request as flush request in
q->prepare_flush_fn because it needs to identify them later (e.g. in
q->request_fn or prep_rq_fn).
queue_flush sets REQ_HARDBARRIER in rq->cmd_flags however the block
layer also sends normal REQ_TYPE_FS requests with REQ_HARDBARRIER. So
SCSI-ml can't use REQ_HARDBARRIER to identify flush requests.
We could change the block layer to clear REQ_HARDBARRIER bit before
sending non flush requests to the lower layers. However, intorudcing
the new flag looks cleaner (surely easier).
Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
---
block/blk-barrier.c | 2 +-
include/linux/bio.h | 2 ++
2 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 4646f6d..ce4e9b8 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -143,7 +143,7 @@ static void queue_flush(struct request_queue *q, unsigned which)
}
blk_rq_init(q, rq);
- rq->cmd_flags = REQ_HARDBARRIER;
+ rq->cmd_flags = REQ_HARDBARRIER | REQ_FLUSH;
rq->rq_disk = q->orig_bar_rq->rq_disk;
rq->end_io = end_io;
q->prepare_flush_fn(q, rq);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 4d379c8..331bd0a 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -152,6 +152,7 @@ enum rq_flag_bits {
__REQ_SYNC, /* request is sync (sync write or read) */
__REQ_META, /* metadata io request */
__REQ_DISCARD, /* request to discard sectors */
+ __REQ_FLUSH, /* request for cache flush */
__REQ_NOIDLE, /* don't anticipate more IO after this one */
/* bio only flags */
@@ -187,6 +188,7 @@ enum rq_flag_bits {
#define REQ_SYNC (1 << __REQ_SYNC)
#define REQ_META (1 << __REQ_META)
#define REQ_DISCARD (1 << __REQ_DISCARD)
+#define REQ_FLUSH (1 << __REQ_FLUSH)
#define REQ_NOIDLE (1 << __REQ_NOIDLE)
#define REQ_FAILFAST_MASK \
--
1.6.5
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