We can't wait for polled events to complete, as they may require active
polling from whoever submitted it. If that is the same task that is
submitting new IO, we could deadlock waiting for IO to complete that
this task is supposed to be completing itself.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
fs/block_dev.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 6de8d35f6e41..ebc3d5a0f424 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -402,8 +402,16 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
if (!nr_pages) {
- if (iocb->ki_flags & IOCB_HIPRI)
+ if (iocb->ki_flags & IOCB_HIPRI) {
bio->bi_opf |= REQ_HIPRI;
+ /*
+ * For async polled IO, we can't wait for
+ * requests to complete, as they may also be
+ * polled and require active reaping.
+ */
+ if (!is_sync)
+ bio->bi_opf |= REQ_NOWAIT;
+ }
qc = submit_bio(bio);
WRITE_ONCE(iocb->ki_cookie, qc);
--
2.17.1
