From 0bbb280d7b767e7c86a5adfc87c76a6f09ab0423 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 21 Dec 2018 09:10:46 -0700 Subject: [PATCH] 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: Hannes Reinecke Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- fs/block_dev.c | 4 ++-- include/linux/bio.h | 14 ++++++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index 1fe498b08f1b..e9faa52bb489 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -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; } diff --git a/include/linux/bio.h b/include/linux/bio.h index bdd11d4c2f05..bb6090aa165d 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -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 */