From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Jens Axboe To: linux-block@vger.kernel.org Cc: Jens Axboe Subject: [PATCH 4/6] block: avoid ordered task state change for polled IO Date: Sat, 10 Nov 2018 08:13:15 -0700 Message-Id: <20181110151317.3813-5-axboe@kernel.dk> In-Reply-To: <20181110151317.3813-1-axboe@kernel.dk> References: <20181110151317.3813-1-axboe@kernel.dk> List-ID: We only really need the barrier if we're going to be sleeping, if we're just polling we're fine with the __set_current_state() variant. Signed-off-by: Jens Axboe --- fs/block_dev.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index c039abfb2052..e7550b1f9670 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -237,12 +237,23 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter, qc = submit_bio(&bio); for (;;) { - set_current_state(TASK_UNINTERRUPTIBLE); + /* + * Using non-atomic task state for polling + */ + __set_current_state(TASK_UNINTERRUPTIBLE); + if (!READ_ONCE(bio.bi_private)) break; + if (!(iocb->ki_flags & IOCB_HIPRI) || - !blk_poll(bdev_get_queue(bdev), qc)) + !blk_poll(bdev_get_queue(bdev), qc)) { + /* + * If we're scheduling, ensure that task state + * change is ordered and seen. + */ + smp_mb(); io_schedule(); + } } __set_current_state(TASK_RUNNING); @@ -403,13 +414,19 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) return -EIOCBQUEUED; for (;;) { - set_current_state(TASK_UNINTERRUPTIBLE); + /* + * See __blkdev_direct_IO_simple() loop + */ + __set_current_state(TASK_UNINTERRUPTIBLE); + if (!READ_ONCE(dio->waiter)) break; if (!(iocb->ki_flags & IOCB_HIPRI) || - !blk_poll(bdev_get_queue(bdev), qc)) + !blk_poll(bdev_get_queue(bdev), qc)) { + smp_mb(); io_schedule(); + } } __set_current_state(TASK_RUNNING); -- 2.17.1