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block: ignore RWF_HIPRI hint for sync dio 

So far bio is marked as REQ_POLLED if RWF_HIPRI/IOCB_HIPRI is passed
from userspace sync io interface, then block layer tries to poll until
the bio is completed. But the current implementation calls
blk_io_schedule() if bio_poll() returns 0, and this way causes io hang or
timeout easily.

But looks no one reports this kind of issue, which should have been
triggered in normal io poll sanity test or blktests block/007 as
observed by Changhui, that means it is very likely that no one uses it
or no one cares it.

Also after io_uring is invented, io poll for sync dio becomes legacy
interface.

So ignore RWF_HIPRI hint for sync dio.

CC: linux-mm@kvack.org
Cc: linux-xfs@vger.kernel.org
Reported-by: Changhui Zhong <czhong@redhat.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Changhui Zhong <czhong@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220420143110.2679002-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2022-04-20 22:31:10 +08:00 committed by Jens Axboe
parent e233fe1aa0
commit 9650b453a3
3 changed files with 5 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
block/fops.c
View File

@ -44,14 +44,6 @@ static unsigned int dio_bio_write_op(struct kiocb *iocb)
#define DIO_INLINE_BIO_VECS 4
static void blkdev_bio_end_io_simple(struct bio *bio)
{
struct task_struct *waiter = bio->bi_private;
WRITE_ONCE(bio->bi_private, NULL);
blk_wake_io_task(waiter);
}
static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
struct iov_iter *iter, unsigned int nr_pages)
{
@ -83,8 +75,6 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
bio_init(&bio, bdev, vecs, nr_pages, dio_bio_write_op(iocb));
}
bio.bi_iter.bi_sector = pos >> SECTOR_SHIFT;
bio.bi_private = current;
bio.bi_end_io = blkdev_bio_end_io_simple;
bio.bi_ioprio = iocb->ki_ioprio;
ret = bio_iov_iter_get_pages(&bio, iter);
@ -97,18 +87,8 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
if (iocb->ki_flags & IOCB_NOWAIT)
bio.bi_opf |= REQ_NOWAIT;
if (iocb->ki_flags & IOCB_HIPRI)
bio_set_polled(&bio, iocb);
submit_bio(&bio);
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!READ_ONCE(bio.bi_private))
break;
if (!(iocb->ki_flags & IOCB_HIPRI) || !bio_poll(&bio, NULL, 0))
blk_io_schedule();
}
__set_current_state(TASK_RUNNING);
submit_bio_wait(&bio);
bio_release_pages(&bio, should_dirty);
if (unlikely(bio.bi_status))

7
fs/iomap/direct-io.c
View File

@ -56,7 +56,8 @@ static void iomap_dio_submit_bio(const struct iomap_iter *iter,
{
atomic_inc(&dio->ref);
if (dio->iocb->ki_flags & IOCB_HIPRI) {
/* Sync dio can't be polled reliably */
if ((dio->iocb->ki_flags & IOCB_HIPRI) && !is_sync_kiocb(dio->iocb)) {
bio_set_polled(bio, dio->iocb);
dio->submit.poll_bio = bio;
}
@ -653,9 +654,7 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
if (!READ_ONCE(dio->submit.waiter))
break;
if (!dio->submit.poll_bio ||
!bio_poll(dio->submit.poll_bio, NULL, 0))
blk_io_schedule();
blk_io_schedule();
}
__set_current_state(TASK_RUNNING);
}

4
mm/page_io.c
View File

@ -360,7 +360,6 @@ int swap_readpage(struct page *page, bool synchronous)
* attempt to access it in the page fault retry time check.
*/
if (synchronous) {
bio->bi_opf |= REQ_POLLED;
get_task_struct(current);
bio->bi_private = current;
}
@ -372,8 +371,7 @@ int swap_readpage(struct page *page, bool synchronous)
if (!READ_ONCE(bio->bi_private))
break;
if (!bio_poll(bio, NULL, 0))
blk_io_schedule();
blk_io_schedule();
}
__set_current_state(TASK_RUNNING);
bio_put(bio);