2 files changed, 45 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c82ce1fd8723..f78b1964543b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5880,6 +5880,49 @@ raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
                                 raid5_store_stripe_cache_size);
 
 static ssize_t
+raid5_show_rmw_level(struct mddev  *mddev, char *page)
+{
+        struct r5conf *conf = mddev->private;
+        if (conf)
+                return sprintf(page, "%d\n", conf->rmw_level);
+        else
+                return 0;
+}
+
+static ssize_t
+raid5_store_rmw_level(struct mddev  *mddev, const char *page, size_t len)
+{
+        struct r5conf *conf = mddev->private;
+        unsigned long new;
+
+        if (!conf)
+                return -ENODEV;
+
+        if (len >= PAGE_SIZE)
+                return -EINVAL;
+
+        if (kstrtoul(page, 10, &new))
+                return -EINVAL;
+
+        if (new != PARITY_DISABLE_RMW && !raid6_call.xor_syndrome)
+                return -EINVAL;
+
+        if (new != PARITY_DISABLE_RMW &&
+            new != PARITY_ENABLE_RMW &&
+            new != PARITY_PREFER_RMW)
+                return -EINVAL;
+
+        conf->rmw_level = new;
+        return len;
+}
+
+static struct md_sysfs_entry
+raid5_rmw_level = __ATTR(rmw_level, S_IRUGO | S_IWUSR,
+                         raid5_show_rmw_level,
+                         raid5_store_rmw_level);
+
+
+static ssize_t
 raid5_show_preread_threshold(struct mddev *mddev, char *page)
 {
         struct r5conf *conf;
@@ -6065,6 +6108,7 @@ static struct attribute *raid5_attrs[] =  {
         &raid5_preread_bypass_threshold.attr,
         &raid5_group_thread_cnt.attr,
         &raid5_skip_copy.attr,
+        &raid5_rmw_level.attr,
         NULL,
 };
 static struct attribute_group raid5_attrs_group = {
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 57fef9ba36fa..6614ac5ffc0e 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -362,6 +362,7 @@ enum {
 enum {
         PARITY_DISABLE_RMW = 0,
         PARITY_ENABLE_RMW,
+        PARITY_PREFER_RMW,
 };
 
 /*