Commit 0bbb280d authored by Jens Axboe's avatar Jens Axboe
Browse files

block: add bio_set_polled() helper 



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.

Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent eae83ce1

fs/block_dev.c

+2 −2
Original line number Diff line number Diff line
@@ -248,7 +248,7 @@ __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 (;;) {
@@ -419,7 +419,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) 
			bool polled = false;



			if (iocb->ki_flags & IOCB_HIPRI) {

				bio->bi_opf |= REQ_HIPRI;

				bio_set_polled(bio, iocb);

				polled = true;

			}

include/linux/bio.h

+14 −0
Original line number Diff line number Diff line
@@ -826,5 +826,19 @@ 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 */

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