[PATCH 6.18.y 1/6] nvdimm: preserve flush callback -ENOMEM

[Sasha Levin <sashal@kernel.org>]

From: Li Chen <me@linux.beauty>

[ Upstream commit 6b7108712a4b1c37cac69815aede1dde202b3187 ]

nvdimm_flush() maps provider flush failures to -EIO. Keep that default
because provider callbacks can report host-side or backend failures that
should remain generic I/O errors to the guest.

Guest-side allocation failures should not be reported as I/O errors. In the
virtio-pmem path, the flush request allocation can fail with -ENOMEM before
any request is submitted to the host. Mapping that to -EIO makes resource
pressure look like media failure.

Preserve -ENOMEM from provider callbacks and continue to map other non-zero
provider failures to -EIO. The generic flush path still returns 0, and
pmem_submit_bio() already converts errno values to block status for bio
completion.

Suggested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: Li Chen <me@linux.beauty>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260630092338.2094628-2-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/region_devs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 5a1c68c701cfc..92d835c8dd168 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1094,7 +1094,8 @@ int nvdimm_flush(struct nd_region *nd_region, struct bio *bio)
 	if (!nd_region->flush)
 		rc = generic_nvdimm_flush(nd_region);
 	else {
-		if (nd_region->flush(nd_region, bio))
+		rc = nd_region->flush(nd_region, bio);
+		if (rc && rc != -ENOMEM)
 			rc = -EIO;
 	}
 
-- 
2.53.0