block: add REQ_HIPRI and inherit it from IOCB_HIPRI

We use IOCB_HIPRI to poll for IO in the caller instead of scheduling.
This information is not available for (or after) IO submission. The
driver may make different queue choices based on the type of IO, so
make the fact that we will poll for this IO known to the lower layers
as well.
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/block_dev.c

@@ -232,6 +232,8 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 		bio.bi_opf = dio_bio_write_op(iocb);
 		task_io_account_write(ret);
 	}
+	if (iocb->ki_flags & IOCB_HIPRI)
+		bio.bi_opf |= REQ_HIPRI;
 
 	qc = submit_bio(&bio);
 	for (;;) {

fs/direct-io.c

@@ -1265,6 +1265,8 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 	} else {
 		dio->op = REQ_OP_READ;
 	}
+	if (iocb->ki_flags & IOCB_HIPRI)
+		dio->op_flags |= REQ_HIPRI;
 
 	/*
 	 * For AIO O_(D)SYNC writes we need to defer completions to a workqueue

fs/iomap.c

@@ -1553,6 +1553,7 @@ iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
 		unsigned len)
 {
 	struct page *page = ZERO_PAGE(0);
+	int flags = REQ_SYNC | REQ_IDLE;
 	struct bio *bio;
 
 	bio = bio_alloc(GFP_KERNEL, 1);
@@ -1561,9 +1562,12 @@ iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
 	bio->bi_private = dio;
 	bio->bi_end_io = iomap_dio_bio_end_io;
 
+	if (dio->iocb->ki_flags & IOCB_HIPRI)
+		flags |= REQ_HIPRI;
+
 	get_page(page);
 	__bio_add_page(bio, page, len, 0);
-	bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC | REQ_IDLE);
+	bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
 
 	atomic_inc(&dio->ref);
 	return submit_bio(bio);
@@ -1662,6 +1666,9 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
 				bio_set_pages_dirty(bio);
 		}
 
+		if (dio->iocb->ki_flags & IOCB_HIPRI)
+			bio->bi_opf |= REQ_HIPRI;
+
 		iov_iter_advance(dio->submit.iter, n);
 
 		dio->size += n;

include/linux/blk_types.h

@@ -323,6 +323,8 @@ enum req_flag_bits {
 	/* command specific flags for REQ_OP_WRITE_ZEROES: */
 	__REQ_NOUNMAP,		/* do not free blocks when zeroing */
 
+	__REQ_HIPRI,
+
 	/* for driver use */
 	__REQ_DRV,
 	__REQ_SWAP,		/* swapping request. */
@@ -343,8 +345,8 @@ enum req_flag_bits {
 #define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
 #define REQ_BACKGROUND		(1ULL << __REQ_BACKGROUND)
 #define REQ_NOWAIT		(1ULL << __REQ_NOWAIT)
-
 #define REQ_NOUNMAP		(1ULL << __REQ_NOUNMAP)
+#define REQ_HIPRI		(1ULL << __REQ_HIPRI)
 
 #define REQ_DRV			(1ULL << __REQ_DRV)
 #define REQ_SWAP		(1ULL << __REQ_SWAP)