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>
---
diff --git a/block/fops.c b/block/fops.c
index 50d245e8c913..a03cb732c2a7 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -368,6 +368,14 @@ static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
return __blkdev_direct_IO_async(iocb, iter, nr_pages);
}
+ /*
+ * We're doing more than a bio worth of IO (> 256 pages), and we
+ * cannot guarantee that one of the sub bios will not fail getting
+ * issued FOR NOWAIT as error results are coalesced across all of
+ * them. Be safe and ask for a retry of this from blocking context.
+ */
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ return -EAGAIN;
return __blkdev_direct_IO(iocb, iter, bio_max_segs(nr_pages));
}
--
Jens Axboe
