[PATCH 02/16] block: don't try to poll multi-bio I/Os in __blkdev_direct_IO

Christoph Hellwig
2021-06-15T14:46:21Z

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@lst.de>
---
fs/block_dev.c | 21 +++++++--------------
1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index ac9b3c158a77..8600c651b0b0 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 do_poll = (iocb->ki_flags & IOCB_HIPRI);
bool is_read = (iov_iter_rw(iter) == READ), is_sync;
loff_t pos = iocb->ki_pos;
blk_qc_t qc = BLK_QC_T_NONE;
@@ -404,7 +404,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
* Don't plug for HIPRI/polled IO, as those should go straight
* to issue
*/
- if (!is_poll)
+ if (!(iocb->ki_flags & IOCB_HIPRI))
blk_start_plug(&plug);

for (;;) {
@@ -438,20 +438,13 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,

nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS);
if (!nr_pages) {
- bool polled = false;
-
- if (iocb->ki_flags & IOCB_HIPRI) {
+ if (do_poll)
bio_set_polled(bio, iocb);
- polled = true;
- }
-
qc = submit_bio(bio);
-
- if (polled)
+ if (do_poll)
WRITE_ONCE(iocb->ki_cookie, qc);
break;
}
-
if (!dio->multi_bio) {
/*
* AIO needs an extra reference to ensure the dio
@@ -462,6 +455,7 @@ 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);
+ do_poll = false;
} else {
atomic_inc(&dio->ref);
}
@@ -470,7 +464,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
bio = bio_alloc(GFP_KERNEL, nr_pages);
}

- if (!is_poll)
+ if (!(iocb->ki_flags & IOCB_HIPRI))
blk_finish_plug(&plug);

if (!is_sync)
@@ -481,8 +475,7 @@ 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);