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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 <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-11-13 21:16:54 -07:00
parent e504545446
commit 0619317ff8
4 changed files with 17 additions and 4 deletions
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4
fs/block_dev.c
View File

@ -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);
}
}

2
fs/iomap.c
View File

@ -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);

13
include/linux/blkdev.h
View File

@ -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

2
mm/page_io.c
View File

@ -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);
}