-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Jens Axboe <axboe@kernel.dk>
-Date: Mon, 16 Jan 2023 08:55:53 -0700
-Subject: [PATCH] block: don't allow multiple bios for IOCB_NOWAIT issue
-
-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@vger.kernel.org # 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@microsoft.com>
-Signed-off-by: Jens Axboe <axboe@kernel.dk>
-(commit 67d59247d4b52c917e373f05a807027756ab216f upstream)
-Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
-Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
----
- block/fops.c | 21 ++++++++++++++++++---
- 1 file changed, 18 insertions(+), 3 deletions(-)
-
-diff --git a/block/fops.c b/block/fops.c
-index 50d245e8c913..d2e6be4e3d1c 100644
---- a/block/fops.c
-+++ b/block/fops.c
-@@ -221,6 +221,24 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
- bio_endio(bio);
- break;
- }
-+ if (iocb->ki_flags & IOCB_NOWAIT) {
-+ /*
-+ * This is nonblocking IO, and we need to allocate
-+ * another bio if we have data left to map. As we
-+ * cannot guarantee that one of the sub bios will not
-+ * fail getting issued FOR NOWAIT and as error results
-+ * are coalesced across all of them, be safe and ask for
-+ * a retry of this from blocking context.
-+ */
-+ 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) {
- if (dio->flags & DIO_SHOULD_DIRTY)
-@@ -228,9 +246,6 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
- } else {
- 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;
-