libnvdimm: check and clear poison before writing to pmem

We need to clear any poison when we are writing to pmem. The granularity
will be sector size. If it's less then we can't do anything about it
barring corruption.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
[djbw: fixup 0-length write request to succeed]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/claim.c

@@ -226,24 +226,46 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 		resource_size_t offset, void *buf, size_t size, int rw)
 {
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
+	unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
+	sector_t sector = offset >> 9;
+	int rc = 0;
+
+	if (unlikely(!size))
+		return 0;
 
 	if (unlikely(offset + size > nsio->size)) {
 		dev_WARN_ONCE(&ndns->dev, 1, "request out of range\n");
 		return -EFAULT;
 	}
 
 	if (rw == READ) {
-		unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
-
-		if (unlikely(is_bad_pmem(&nsio->bb, offset / 512, sz_align)))
+		if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align)))
 			return -EIO;
 		return memcpy_from_pmem(buf, nsio->addr + offset, size);
 	} else {
+
+		if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) {
+			if (IS_ALIGNED(offset, 512) && IS_ALIGNED(size, 512)) {
+				long cleared;
+
+				cleared = nvdimm_clear_poison(&ndns->dev,
+							      offset, size);
+				if (cleared != size) {
+					size = cleared;
+					rc = -EIO;
+				}
+
+				badblocks_clear(&nsio->bb, sector,
+						cleared >> 9);
+			} else
+				rc = -EIO;
+		}
+
 		memcpy_to_pmem(nsio->addr + offset, buf, size);
 		nvdimm_flush(to_nd_region(ndns->dev.parent));
 	}
 
-	return 0;
+	return rc;
 }
 
 int devm_nsio_enable(struct device *dev, struct nd_namespace_io *nsio)