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block: avoid ordered task state change for polled IO

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For the core poll helper, the task state setting don't need to imply any
atomics, as it's the current task itself that is being modified and
we're not going to sleep.

For IRQ driven, the wakeup path have the necessary barriers to not need
us using the heavy handed version of the task state setting.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-11-16 08:37:34 -07:00
parent a4668d9ba4
commit 849a370016
4 changed files with 11 additions and 6 deletions
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4
block/blk-mq.c
View File

@ -3331,12 +3331,12 @@ static bool __blk_mq_poll(struct blk_mq_hw_ctx *hctx, struct request *rq)
ret = q->mq_ops->poll(hctx, rq->tag);
if (ret > 0) {
hctx->poll_success++;
set_current_state(TASK_RUNNING);
__set_current_state(TASK_RUNNING);
return true;
}
if (signal_pending_state(state, current))
set_current_state(TASK_RUNNING);
__set_current_state(TASK_RUNNING);
if (current->state == TASK_RUNNING)
return true;

7
fs/block_dev.c
View File

@ -237,9 +237,11 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
qc = submit_bio(&bio);
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
__set_current_state(TASK_UNINTERRUPTIBLE);
if (!READ_ONCE(bio.bi_private))
break;
if (!(iocb->ki_flags & IOCB_HIPRI) ||
!blk_poll(bdev_get_queue(bdev), qc))
io_schedule();
@ -415,7 +417,8 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
return -EIOCBQUEUED;
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
__set_current_state(TASK_UNINTERRUPTIBLE);
if (!READ_ONCE(dio->waiter))
break;

3
fs/iomap.c
View File

@ -1888,7 +1888,8 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
return -EIOCBQUEUED;
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
__set_current_state(TASK_UNINTERRUPTIBLE);
if (!READ_ONCE(dio->submit.waiter))
break;

3
mm/page_io.c
View File

@ -405,7 +405,8 @@ int swap_readpage(struct page *page, bool synchronous)
bio_get(bio);
qc = submit_bio(bio);
while (synchronous) {
set_current_state(TASK_UNINTERRUPTIBLE);
__set_current_state(TASK_UNINTERRUPTIBLE);
if (!READ_ONCE(bio->bi_private))
break;