@@ -233,7 +233,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
task_io_account_write(ret);
}
if (iocb->ki_flags & IOCB_HIPRI)
- bio.bi_opf |= REQ_HIPRI;
+ bio_set_polled(&bio, iocb);
qc = submit_bio(&bio);
for (;;) {
@@ -401,7 +401,7 @@ __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)
- bio->bi_opf |= REQ_HIPRI;
+ bio_set_polled(bio, iocb);
qc = submit_bio(bio);
WRITE_ONCE(iocb->ki_cookie, qc);
@@ -823,5 +823,19 @@ static inline int bio_integrity_add_page(struct bio *bio, struct page *page,
#endif /* CONFIG_BLK_DEV_INTEGRITY */
+/*
+ * Mark a bio as polled. Note that for async polled IO, the caller must
+ * expect -EWOULDBLOCK if we cannot allocate a request (or other resources).
+ * We cannot block waiting for requests on polled IO, as those completions
+ * must be found by the caller. This is different than IRQ driven IO, where
+ * it's safe to wait for IO to complete.
+ */
+static inline void bio_set_polled(struct bio *bio, struct kiocb *kiocb)
+{
+ bio->bi_opf |= REQ_HIPRI;
+ if (!is_sync_kiocb(kiocb))
+ bio->bi_opf |= REQ_NOWAIT;
+}
+
#endif /* CONFIG_BLOCK */
#endif /* __LINUX_BIO_H */
For the upcoming async polled IO, we can't sleep allocating requests. If we do, then we introduce a deadlock where the submitter already has async polled IO in-flight, but can't wait for them to complete since polled requests must be active found and reaped. Utilize the helper in the blockdev DIRECT_IO code. Signed-off-by: Jens Axboe <axboe@kernel.dk> --- fs/block_dev.c | 4 ++-- include/linux/bio.h | 14 ++++++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-)