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block: add bio_set_polled() helper

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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 <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-12-21 09:10:46 -07:00
parent eae83ce10b
commit 0bbb280d7b
2 changed files with 16 additions and 2 deletions
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4
fs/block_dev.c
View File

@ -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;
}

14
include/linux/bio.h
View File

@ -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 */