[PATCH 09/16] io_uring: don't sleep when polling for I/O

Christoph Hellwig
2021-06-15T14:36:49Z

There is no point in sleeping for the expected I/O completion timeout
in the io_uring async polling model as we never poll for a specific
I/O.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
---
block/blk-mq.c | 3 ++-
fs/io_uring.c | 2 +-
include/linux/blkdev.h | 2 ++
3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c2b2c7abd712..86e59ffcca44 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4002,7 +4002,8 @@ int blk_poll(struct request_queue *q, blk_qc_t cookie, unsigned int flags)
if (current->plug)
blk_flush_plug_list(current->plug, false);

- if (q->poll_nsec != BLK_MQ_POLL_CLASSIC) {
+ if (!(flags & BLK_POLL_NOSLEEP) &&
+ q->poll_nsec != BLK_MQ_POLL_CLASSIC) {
if (blk_mq_poll_hybrid(q, cookie))
return 1;
}
diff --git a/fs/io_uring.c b/fs/io_uring.c
index de8d39e9a154..6ce1e5b60725 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2290,7 +2290,7 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
long min)
{
- unsigned int poll_flags = 0;
+ unsigned int poll_flags = BLK_POLL_NOSLEEP;
struct io_kiocb *req, *tmp;
LIST_HEAD(done);
int ret = 0;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c7061f25ee5f..821d721f78e7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -948,6 +948,8 @@ blk_status_t errno_to_blk_status(int errno);

/* only poll the hardware once, don't continue until a completion was found */
#define BLK_POLL_ONESHOT (1 << 0)
+/* do not sleep to wait for the expected completion time */
+#define BLK_POLL_NOSLEEP (1 << 1)
int blk_poll(struct request_queue *q, blk_qc_t cookie, unsigned int flags);

static inline struct request_queue *bdev_get_queue(struct block_device *bdev)