If we're doing a large IO request which needs to be split into multiple
bios for issue, then we can run into the same situation as the below
marked commit fixes - parts will complete just fine, one or more parts
will fail to allocate a request. This will result in a partially
completed read or write request, where the caller gets EAGAIN even though
parts of the IO completed just fine.
Do the same for large bios as we do for splits - fail a NOWAIT request
with EAGAIN. This isn't technically fixing an issue in the below marked
patch, but for stable purposes, we should have either none of them or
both.
This depends on: 613b14884b85 ("block: handle bio_split_to_limits() NULL return")
Cc: stable@xxxxxxxxxxxxxxx # 5.15+
Fixes: 9cea62b2cbab ("block: don't allow splitting of a REQ_NOWAIT bio")
Link: https://github.com/axboe/liburing/issues/766
Reported-and-tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---
This is a backport to v5.15.90 of a patch[1] from Jens Axboe. I've
tested the backport with my basic io_uring tests, but the code
should be reviewed in the context of 5.15.90. Commit 613b14884b85
mentioned above has already been backported and included in v5.15.90.
[1] https://lore.kernel.org/linux-block/1ce71005-c81b-374d-5bcf-e3b7e7c48d0d@xxxxxxxxx/
block/fops.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/block/fops.c b/block/fops.c
index 1e970c2..42dafe7 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -244,17 +244,25 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
break;
}
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (unlikely(iov_iter_count(iter))) {
+ bio_release_pages(bio, false);
+ bio_clear_flag(bio, BIO_REFFED);
+ bio_put(bio);
+ blk_finish_plug(&plug);
+ return -EAGAIN;
+ }
+ bio->bi_opf |= REQ_NOWAIT;
+ }
+
if (is_read) {
- bio->bi_opf = REQ_OP_READ;
+ bio->bi_opf |= REQ_OP_READ;
if (dio->should_dirty)
bio_set_pages_dirty(bio);
} else {
- bio->bi_opf = dio_bio_write_op(iocb);
+ bio->bi_opf |= dio_bio_write_op(iocb);
task_io_account_write(bio->bi_iter.bi_size);
}
- if (iocb->ki_flags & IOCB_NOWAIT)
- bio->bi_opf |= REQ_NOWAIT;
-
dio->size += bio->bi_iter.bi_size;
pos += bio->bi_iter.bi_size;
--
1.8.3.1
