[PATCH v4 1/7] nvdimm: preserve flush callback errors

[Li Chen <me@linux.beauty>]

nvdimm_flush() currently converts any non-zero provider flush error to
-EIO. That loses useful errno values from provider callbacks.

A local virtio-pmem mkfs sanity test showed the masking clearly:

  wipefs: /dev/pmem0: cannot flush modified buffers: Input/output error
  mkfs.ext4: Input/output error while writing out and closing file system
  nd_region region0: dbg: nvdimm_flush rc=-5

The virtio-pmem callback can return -ENOMEM when async_pmem_flush() fails
to allocate a child flush bio, but nvdimm_flush() hides that as -EIO before
pmem_submit_bio() converts it to a block status.

Return the provider callback error directly. The generic flush path still
returns 0, and pmem_submit_bio() already handles errno-to-blk_status
conversion for bio completion.

Signed-off-by: Li Chen <me@linux.beauty>
---
v3->v4:
- New patch.

 drivers/nvdimm/region_devs.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index e35c2e18518f0..0cd96503c0596 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1114,10 +1114,8 @@ 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 = -EIO;
-	}
+	else
+		rc = nd_region->flush(nd_region, bio);
 
 	return rc;
 }
-- 
2.52.0