[PATCH 6.6.y 2/6] nvdimm: pmem: keep PREFLUSH before data writes

[Sasha Levin <sashal@kernel.org>]

From: Li Chen <me@linux.beauty>

[ Upstream commit c644a2f8fef5618fcf453c591177700fd07dd024 ]

pmem_submit_bio() records a REQ_PREFLUSH error, but continues to copy the
bio data and can later overwrite the error with a successful REQ_FUA flush.
That lets data writes run after a failed preflush and can complete the bio
successfully despite the failed ordering barrier.

Run the REQ_PREFLUSH flush synchronously before touching the bio data and
complete the bio with the flush error if it fails. Keep asynchronous flush
chaining for REQ_FUA. At that point, data copy has completed and the parent
bio can wait for the chained flush bio.

Signed-off-by: Li Chen <me@linux.beauty>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260630092338.2094628-3-me@linux.beauty>
Stable-dep-of: e57140944b5a ("nvdimm: virtio_pmem: refcount requests for token lifetime")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/nvdimm/pmem.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 4e8fdcb3f1c82..e82c8e7ec3720 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -209,8 +209,14 @@ static void pmem_submit_bio(struct bio *bio)
 	struct pmem_device *pmem = bio->bi_bdev->bd_disk->private_data;
 	struct nd_region *nd_region = to_region(pmem);
 
-	if (bio->bi_opf & REQ_PREFLUSH)
-		ret = nvdimm_flush(nd_region, bio);
+	if (bio->bi_opf & REQ_PREFLUSH) {
+		ret = nvdimm_flush(nd_region, NULL);
+		if (ret) {
+			bio->bi_status = errno_to_blk_status(ret);
+			bio_endio(bio);
+			return;
+		}
+	}
 
 	do_acct = blk_queue_io_stat(bio->bi_bdev->bd_disk->queue);
 	if (do_acct)
@@ -230,7 +236,7 @@ static void pmem_submit_bio(struct bio *bio)
 	if (do_acct)
 		bio_end_io_acct(bio, start);
 
-	if (bio->bi_opf & REQ_FUA)
+	if ((bio->bi_opf & REQ_FUA) && !bio->bi_status)
 		ret = nvdimm_flush(nd_region, bio);
 
 	if (ret)
-- 
2.53.0