From 0619317ff8baa2da9238191ad5167ed3618c16d9 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 13 Nov 2018 21:16:54 -0700 Subject: [PATCH] block: add polled wakeup task helper If we're polling for IO on a device that doesn't use interrupts, then IO completion loop (and wake of task) is done by submitting task itself. If that is the case, then we don't need to enter the wake_up_process() function, we can simply mark ourselves as TASK_RUNNING. Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/block_dev.c | 4 ++-- fs/iomap.c | 2 +- include/linux/blkdev.h | 13 +++++++++++++ mm/page_io.c | 2 +- 4 files changed, 17 insertions(+), 4 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index c039abfb205203..9fe56672cfe51a 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -181,7 +181,7 @@ static void blkdev_bio_end_io_simple(struct bio *bio) struct task_struct *waiter = bio->bi_private; WRITE_ONCE(bio->bi_private, NULL); - wake_up_process(waiter); + blk_wake_io_task(waiter); } static ssize_t @@ -305,7 +305,7 @@ static void blkdev_bio_end_io(struct bio *bio) struct task_struct *waiter = dio->waiter; WRITE_ONCE(dio->waiter, NULL); - wake_up_process(waiter); + blk_wake_io_task(waiter); } } diff --git a/fs/iomap.c b/fs/iomap.c index f61d13dfdf0958..b0462b363badff 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -1525,7 +1525,7 @@ static void iomap_dio_bio_end_io(struct bio *bio) if (dio->wait_for_completion) { struct task_struct *waiter = dio->submit.waiter; WRITE_ONCE(dio->submit.waiter, NULL); - wake_up_process(waiter); + blk_wake_io_task(waiter); } else if (dio->flags & IOMAP_DIO_WRITE) { struct inode *inode = file_inode(dio->iocb->ki_filp); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 41aaa05e42c1e2..91c44f7a7f62b7 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1772,4 +1772,17 @@ static inline int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask, #endif /* CONFIG_BLOCK */ +static inline void blk_wake_io_task(struct task_struct *waiter) +{ + /* + * If we're polling, the task itself is doing the completions. For + * that case, we don't need to signal a wakeup, it's enough to just + * mark us as RUNNING. + */ + if (waiter == current) + __set_current_state(TASK_RUNNING); + else + wake_up_process(waiter); +} + #endif diff --git a/mm/page_io.c b/mm/page_io.c index d4d1c89bcdddce..57572ff46016dd 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -140,7 +140,7 @@ static void end_swap_bio_read(struct bio *bio) unlock_page(page); WRITE_ONCE(bio->bi_private, NULL); bio_put(bio); - wake_up_process(waiter); + blk_wake_io_task(waiter); put_task_struct(waiter); }