On 5/18/18 8:14 AM, Jens Axboe wrote:

On 5/17/18 2:38 PM, adam.manzanares@wdc.com wrote:

quoted

From: Adam Manzanares <redacted>

This is the per-I/O equivalent of the ioprio_set system call.

When IOCB_FLAG_IOPRIO is set on the iocb aio_flags field, then we set the
newly added kiocb ki_ioprio field to the value in the iocb aio_reqprio field.

When a bio is created for an aio request by the block dev we set the priority
value of the bio to the user supplied value.

This patch depends on block: add ioprio_check_cap function

Actually, one comment on this one:

quoted

diff --git a/fs/aio.c b/fs/aio.c
index f3eae5d5771b..ff3107aa82d5 100644
--- a/fs/aio.c
+++ b/fs/aio.c

@@ -1451,6 +1451,22 @@ static int aio_prep_rw(struct kiocb *req, struct iocb *iocb)
  	if (iocb->aio_flags & IOCB_FLAG_RESFD)
  		req->ki_flags |= IOCB_EVENTFD;
  	req->ki_hint = file_write_hint(req->ki_filp);
+	if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
+		/*
+		 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
+		 * aio_reqprio is interpreted as an I/O scheduling
+		 * class and priority.
+		 */
+		ret = ioprio_check_cap(iocb->aio_reqprio);
+		if (ret) {
+			pr_debug("aio ioprio check cap error\n");
+			return -EINVAL;
+		}
+
+		req->ki_ioprio = iocb->aio_reqprio;
+		req->ki_flags |= IOCB_IOPRIO;
+	}

Do we really need IOCB_IOPRIO? All zeroes is no priority set anyway,
so we should be able to get by with just setting ->ki_ioprio to either
the priority, or 0.

quoted

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7ec920e27065..970bef79caa6 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c

@@ -355,6 +355,8 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
  		bio->bi_write_hint = iocb->ki_hint;
  		bio->bi_private = dio;
  		bio->bi_end_io = blkdev_bio_end_io;
+		if (iocb->ki_flags & IOCB_IOPRIO)
+			bio->bi_ioprio = iocb->ki_ioprio;

And then this assignment can just happen unconditionally.

That is a cleaner way of guaranteeing the ioprio set on the kiocb is 
only set when the user intends to use the ioprio from the iocb.

I'll resend the series.

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