[PATCH 02/15] block: don't try to poll multi-bio I/Os in __blkdev_direct_IO

[Christoph Hellwig]

If an iocb is split into multiple bios we can't poll for both.  So don't
bother to even try to poll in that case.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 fs/block_dev.c | 37 ++++++++++++++-----------------------
 1 file changed, 14 insertions(+), 23 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index b8abccd03e5d..0080a3b710b4 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -375,7 +375,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 	struct blk_plug plug;
 	struct blkdev_dio *dio;
 	struct bio *bio;
-	bool is_poll = (iocb->ki_flags & IOCB_HIPRI) != 0;
+	bool is_poll = (iocb->ki_flags & IOCB_HIPRI), do_poll = false;
 	bool is_read = (iov_iter_rw(iter) == READ), is_sync;
 	loff_t pos = iocb->ki_pos;
 	blk_qc_t qc = BLK_QC_T_NONE;
@@ -437,22 +437,9 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 		pos += bio->bi_iter.bi_size;
 
 		nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS);
-		if (!nr_pages) {
-			bool polled = false;
-
-			if (iocb->ki_flags & IOCB_HIPRI) {
-				bio_set_polled(bio, iocb);
-				polled = true;
-			}
-
-			qc = submit_bio(bio);
-
-			if (polled)
-				WRITE_ONCE(iocb->ki_cookie, qc);
-			break;
-		}
-
-		if (!dio->multi_bio) {
+		if (dio->multi_bio) {
+			atomic_inc(&dio->ref);
+		} else if (nr_pages) {
 			/*
 			 * AIO needs an extra reference to ensure the dio
 			 * structure which is embedded into the first bio
@@ -462,11 +449,16 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 				bio_get(bio);
 			dio->multi_bio = true;
 			atomic_set(&dio->ref, 2);
-		} else {
-			atomic_inc(&dio->ref);
+		} else if (is_poll) {
+			bio_set_polled(bio, iocb);
+			do_poll = true;
+		}
+		qc = submit_bio(bio);
+		if (!nr_pages) {
+			if (do_poll)
+				WRITE_ONCE(iocb->ki_cookie, qc);
+			break;
 		}
-
-		submit_bio(bio);
 		bio = bio_alloc(GFP_KERNEL, nr_pages);
 	}
 
@@ -481,8 +473,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 		if (!READ_ONCE(dio->waiter))
 			break;
 
-		if (!(iocb->ki_flags & IOCB_HIPRI) ||
-		    !blk_poll(bdev_get_queue(bdev), qc, true))
+		if (!do_poll || !blk_poll(bdev_get_queue(bdev), qc, true))
 			blk_io_schedule();
 	}
 	__set_current_state(TASK_RUNNING);
-- 
2.30.2