[PATCH 3/8] md: add serialize_policy sysfs node for raid1

[jgq516@xxxxxxxxx]

From: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>

With the new sysfs node, we can use it to control if raid1 array
wants serialization for write request or not.

Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
---
 drivers/md/md.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/md/md.h |  1 +
 2 files changed, 47 insertions(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 43b7da334e4a..8df94a58512b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -174,6 +174,7 @@ void mddev_create_serial_pool(struct mddev *mddev, struct md_rdev *rdev,
 		memalloc_noio_restore(noio_flag);
 		if (!mddev->serial_info_pool)
 			pr_err("can't alloc memory pool for writemostly\n");
+		mddev->serialize_policy = true;
 		if (!is_suspend)
 			mddev_resume(mddev);
 	}
@@ -216,6 +217,7 @@ static void mddev_destroy_serial_pool(struct mddev *mddev, struct md_rdev *rdev,
 			mempool_destroy(mddev->serial_info_pool);
 			mddev->serial_info_pool = NULL;
 		}
+		mddev->serialize_policy = false;
 		mddev_resume(mddev);
 	}
 }
@@ -5261,6 +5263,49 @@ static struct md_sysfs_entry md_fail_last_dev =
 __ATTR(fail_last_dev, S_IRUGO | S_IWUSR, fail_last_dev_show,
        fail_last_dev_store);
 
+static ssize_t serialize_policy_show(struct mddev *mddev, char *page)
+{
+	return sprintf(page, "%d\n", mddev->serialize_policy);
+}
+
+/*
+ * Setting serialize_policy to true to enforce write IO is not reordered
+ * for raid1.
+ */
+static ssize_t
+serialize_policy_store(struct mddev *mddev, const char *buf, size_t len)
+{
+	int err;
+	bool value;
+
+	err = kstrtobool(buf, &value);
+	if (err || value == mddev->serialize_policy)
+		return err ?: -EINVAL;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	if (mddev->pers == NULL ||
+	    (strncmp(mddev->pers->name, "raid1", 4) != 0)) {
+		pr_err("md: serialize_policy is only effective for raid1\n");
+		err = -EINVAL;
+		goto unlock;
+	}
+
+	if (value)
+		mddev_create_serial_pool(mddev, NULL, false, true);
+	else
+		mddev_destroy_serial_pool(mddev, NULL, true);
+unlock:
+	mddev_unlock(mddev);
+	return err ?: len;
+}
+
+static struct md_sysfs_entry md_serialize_policy =
+__ATTR(serialize_policy, S_IRUGO | S_IWUSR, serialize_policy_show,
+       serialize_policy_store);
+
+
 static struct attribute *md_default_attrs[] = {
 	&md_level.attr,
 	&md_layout.attr,
@@ -5278,6 +5323,7 @@ static struct attribute *md_default_attrs[] = {
 	&max_corr_read_errors.attr,
 	&md_consistency_policy.attr,
 	&md_fail_last_dev.attr,
+	&md_serialize_policy.attr,
 	NULL,
 };
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 291a59a94528..161772066dab 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -494,6 +494,7 @@ struct mddev {
 
 	bool	has_superblocks:1;
 	bool	fail_last_dev:1;
+	bool	serialize_policy:1;
 };
 
 enum recovery_flags {
-- 
2.17.1