[PATCH v5 12/16] md/raid5: support config stripe_size by sysfs entry

Yufen Yu
2020-07-02T12:06:24Z

After this patch, 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

stripe_size should not be bigger than PAGE_SIZE, and it requires to be
multiple of 4096.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
drivers/md/raid5.c | 69 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 68 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f0fd01d9122e..a3376a4e4e5c 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6715,7 +6715,74 @@ raid5_show_stripe_size(struct mddev *mddev, char *page)
static ssize_t
raid5_store_stripe_size(struct mddev *mddev, const char *page, size_t len)
{
- return -EINVAL;
+ struct r5conf *conf = mddev->private;
+ unsigned int new;
+ int err;
+ int nr;
+
+ if (len >= PAGE_SIZE)
+ return -EINVAL;
+ if (kstrtouint(page, 10, &new))
+ return -EINVAL;
+ if (!conf)
+ return -ENODEV;
+
+ /*
+ * When PAGE_SZIE is 4096, we don't need to modify stripe_size.
+ * And the value should not be bigger than PAGE_SIZE.
+ * It requires to be multiple of 4096.
+ */
+ if (PAGE_SIZE == 4096 || new % 4096 != 0 ||
+ new > PAGE_SIZE || new == 0)
+ return -EINVAL;
+
+ if (new == conf->stripe_size)
+ return len;
+
+ pr_debug("md/raid: change stripe_size from %u to %u\n",
+ conf->stripe_size, new);
+
+ err = mddev_lock(mddev);
+ if (err)
+ return err;
+
+ if (mddev->sync_thread ||
+ test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
+ mddev->reshape_position != MaxSector ||
+ mddev->sysfs_active) {
+ err = -EBUSY;
+ goto out_unlock;
+ }
+
+ nr = conf->max_nr_stripes;
+
+ /* 1. suspend raid array */
+ mddev_suspend(mddev);
+
+ /* 2. free all old stripe_head */
+ mutex_lock(&conf->cache_size_mutex);
+ shrink_stripes(conf);
+ BUG_ON(conf->max_nr_stripes != 0);
+
+ /* 3. set new stripe_size */
+ conf->stripe_size = new;
+ conf->stripe_shift = ilog2(new) - 9;
+ conf->stripe_sectors = new >> 9;
+
+ /* 4. allocate new stripe_head */
+ if (grow_stripes(conf, nr)) {
+ pr_warn("md/raid:%s: couldn't allocate buffers\n",
+ mdname(mddev));
+ err = -ENOMEM;
+ }
+ mutex_unlock(&conf->cache_size_mutex);
+
+ /* 5. resume raid array */
+ mddev_resume(mddev);
+
+out_unlock:
+ mddev_unlock(mddev);
+ return err ?: len;
}

static struct md_sysfs_entry
--
2.25.4