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authorJens Axboe <axboe@kernel.dk>2023-08-08 11:06:17 -0600
committerJens Axboe <axboe@kernel.dk>2023-08-09 16:04:07 -0600
commit2bc057692599a5b3dc93d75a3dff34f72576355d (patch)
tree35214904def0152e170be6d5d6e858412f122632 /block/fops.c
parentd74f714896fd6268882789ba28e52c9145951403 (diff)
block: don't make REQ_POLLED imply REQ_NOWAIT
Normally these two flags do go together, as the issuer of polled IO generally cannot wait for resources that will get freed as part of IO completion. This is because that very task is the one that will complete the request and free those resources, hence that would introduce a deadlock. But it is possible to have someone else issue the polled IO, eg via io_uring if the request is punted to io-wq. For that case, it's fine to have the task block on IO submission, as it is not the same task that will be completing the IO. It's completely up to the caller to ask for both polled and nowait IO separately! If we don't allow polled IO where IOCB_NOWAIT isn't set in the kiocb, then we can run into repeated -EAGAIN submissions and not make any progress. Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/fops.c')
-rw-r--r--block/fops.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/block/fops.c b/block/fops.c
index a286bf3325c5..838ffada5341 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -358,13 +358,14 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
task_io_account_write(bio->bi_iter.bi_size);
}
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ bio->bi_opf |= REQ_NOWAIT;
+
if (iocb->ki_flags & IOCB_HIPRI) {
- bio->bi_opf |= REQ_POLLED | REQ_NOWAIT;
+ bio->bi_opf |= REQ_POLLED;
submit_bio(bio);
WRITE_ONCE(iocb->private, bio);
} else {
- if (iocb->ki_flags & IOCB_NOWAIT)
- bio->bi_opf |= REQ_NOWAIT;
submit_bio(bio);
}
return -EIOCBQUEUED;