raid5: sysfs entry to control worker thread number

Add a sysfs entry to control running workqueue thread number. If
group_thread_cnt is set to 0, we will disable workqueue offload handling of
stripes.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 60 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 32fa1131cafc..d79ecd903269 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5145,10 +5145,70 @@ stripe_cache_active_show(struct mddev *mddev, char *page)
 static struct md_sysfs_entry
 raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
 
+static ssize_t
+raid5_show_group_thread_cnt(struct mddev *mddev, char *page)
+{
+        struct r5conf *conf = mddev->private;
+        if (conf)
+                return sprintf(page, "%d\n", conf->worker_cnt_per_group);
+        else
+                return 0;
+}
+
+static int alloc_thread_groups(struct r5conf *conf, int cnt);
+static ssize_t
+raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
+{
+        struct r5conf *conf = mddev->private;
+        unsigned long new;
+        int err;
+        struct r5worker_group *old_groups;
+        int old_group_cnt;
+
+        if (len >= PAGE_SIZE)
+                return -EINVAL;
+        if (!conf)
+                return -ENODEV;
+
+        if (kstrtoul(page, 10, &new))
+                return -EINVAL;
+
+        if (new == conf->worker_cnt_per_group)
+                return len;
+
+        mddev_suspend(mddev);
+
+        old_groups = conf->worker_groups;
+        old_group_cnt = conf->worker_cnt_per_group;
+
+        conf->worker_groups = NULL;
+        err = alloc_thread_groups(conf, new);
+        if (err) {
+                conf->worker_groups = old_groups;
+                conf->worker_cnt_per_group = old_group_cnt;
+        } else {
+                if (old_groups)
+                        kfree(old_groups[0].workers);
+                kfree(old_groups);
+        }
+
+        mddev_resume(mddev);
+
+        if (err)
+                return err;
+        return len;
+}
+
+static struct md_sysfs_entry
+raid5_group_thread_cnt = __ATTR(group_thread_cnt, S_IRUGO | S_IWUSR,
+                                raid5_show_group_thread_cnt,
+                                raid5_store_group_thread_cnt);
+
 static struct attribute *raid5_attrs[] =  {
         &raid5_stripecache_size.attr,
         &raid5_stripecache_active.attr,
         &raid5_preread_bypass_threshold.attr,
+        &raid5_group_thread_cnt.attr,
         NULL,
 };
 static struct attribute_group raid5_attrs_group = {