io_uring: don't sleep when polling for I/O

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>
Link: https://lore.kernel.org/r/20211012111226.760968-11-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6609e10..97c24e4 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4103,7 +4103,8 @@ 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 541fec2..c506614 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2457,7 +2457,7 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
                        long min)
 {
        struct io_kiocb *req, *tmp;
-       unsigned int poll_flags = 0;
+       unsigned int poll_flags = BLK_POLL_NOSLEEP;
        LIST_HEAD(done);
 
        /*

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e177346..2b80c98 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -566,6 +566,8 @@ 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)