md/raid5: support config stripe_size by sysfs entry

Adding a new 'stripe_size' sysfs entry to set and show stripe_size.
stripe_size should not be bigger than PAGE_SIZE, and it requires to
be multiple of 4096. We can adjust stripe_size by writing value into
sysfs entry, likely, set stripe_size as 16KB:

          echo 16384 > /sys/block/md1/md/stripe_size

Show current stripe_size value:

          cat /sys/block/md1/md/stripe_size

For PAGE_SIZE is equal to 4096, 'stripe_size' can just be read.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 60cfa397f2d61a9f47e8114f17ab7b2f3c14edc1..40961dd1777b4a2e2b6fdeb4e3105a30983ca993 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6503,6 +6503,77 @@ raid5_rmw_level = __ATTR(rmw_level, S_IRUGO | S_IWUSR,
                         raid5_show_rmw_level,
                         raid5_store_rmw_level);
 
+static ssize_t
+raid5_show_stripe_size(struct mddev  *mddev, char *page)
+{
+       struct r5conf *conf;
+       int ret = 0;
+
+       spin_lock(&mddev->lock);
+       conf = mddev->private;
+       if (conf)
+               ret = sprintf(page, "%lu\n", RAID5_STRIPE_SIZE(conf));
+       spin_unlock(&mddev->lock);
+       return ret;
+}
+
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+static ssize_t
+raid5_store_stripe_size(struct mddev  *mddev, const char *page, size_t len)
+{
+       struct r5conf *conf;
+       unsigned long new;
+       int err;
+
+       if (len >= PAGE_SIZE)
+               return -EINVAL;
+       if (kstrtoul(page, 10, &new))
+               return -EINVAL;
+
+       /*
+        * The value should not be bigger than PAGE_SIZE. It requires to
+        * be multiple of DEFAULT_STRIPE_SIZE.
+        */
+       if (new % DEFAULT_STRIPE_SIZE != 0 || new > PAGE_SIZE || new == 0)
+               return -EINVAL;
+
+       err = mddev_lock(mddev);
+       if (err)
+               return err;
+
+       conf = mddev->private;
+       if (!conf) {
+               err = -ENODEV;
+               goto out_unlock;
+       }
+
+       if (new == conf->stripe_size)
+               goto out_unlock;
+
+       pr_debug("md/raid: change stripe_size from %lu to %lu\n",
+                       conf->stripe_size, new);
+
+       mddev_suspend(mddev);
+       conf->stripe_size = new;
+       conf->stripe_shift = ilog2(new) - 9;
+       conf->stripe_sectors = new >> 9;
+       mddev_resume(mddev);
+
+out_unlock:
+       mddev_unlock(mddev);
+       return err ?: len;
+}
+
+static struct md_sysfs_entry
+raid5_stripe_size = __ATTR(stripe_size, 0644,
+                        raid5_show_stripe_size,
+                        raid5_store_stripe_size);
+#else
+static struct md_sysfs_entry
+raid5_stripe_size = __ATTR(stripe_size, 0444,
+                        raid5_show_stripe_size,
+                        NULL);
+#endif
 
 static ssize_t
 raid5_show_preread_threshold(struct mddev *mddev, char *page)
@@ -6691,6 +6762,7 @@ static struct attribute *raid5_attrs[] =  {
        &raid5_group_thread_cnt.attr,
        &raid5_skip_copy.attr,
        &raid5_rmw_level.attr,
+       &raid5_stripe_size.attr,
        &r5c_journal_mode.attr,
        &ppl_write_hint.attr,
        NULL,