bcache: use delayed kworker fo asynchronous devices registration

This patch changes the asynchronous registration kworker to a delayed
kworker. There is probability queue_work() queues the async registration
kworker to the same CPU (even though very little), then the process
which writing sysfs interface to reigster bcache device may won't return
immeidately. queue_delayed_work() in this patch will delay 10 jiffies
before insert the kworker to run queue, which makes sure the registering
process may always returns to user space in time.

Fixes: 9e23ccf8f0a22 ("bcache: asynchronous devices registration")
Signed-off-by: Coly Li <colyli@suse.de>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 904ea9b..a6e7908 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -19,6 +19,7 @@
 #include <linux/genhd.h>
 #include <linux/idr.h>
 #include <linux/kthread.h>
+#include <linux/workqueue.h>
 #include <linux/module.h>
 #include <linux/random.h>
 #include <linux/reboot.h>
@@ -2380,7 +2381,7 @@ static bool bch_is_open(struct block_device *bdev)
 }
 
 struct async_reg_args {
-       struct work_struct reg_work;
+       struct delayed_work reg_work;
        char *path;
        struct cache_sb *sb;
        struct cache_sb_disk *sb_disk;
@@ -2391,7 +2392,7 @@ static void register_bdev_worker(struct work_struct *work)
 {
        int fail = false;
        struct async_reg_args *args =
-               container_of(work, struct async_reg_args, reg_work);
+               container_of(work, struct async_reg_args, reg_work.work);
        struct cached_dev *dc;
 
        dc = kzalloc(sizeof(*dc), GFP_KERNEL);
@@ -2421,7 +2422,7 @@ static void register_cache_worker(struct work_struct *work)
 {
        int fail = false;
        struct async_reg_args *args =
-               container_of(work, struct async_reg_args, reg_work);
+               container_of(work, struct async_reg_args, reg_work.work);
        struct cache *ca;
 
        ca = kzalloc(sizeof(*ca), GFP_KERNEL);
@@ -2449,11 +2450,12 @@ out:
 static void register_device_aync(struct async_reg_args *args)
 {
        if (SB_IS_BDEV(args->sb))
-               INIT_WORK(&args->reg_work, register_bdev_worker);
+               INIT_DELAYED_WORK(&args->reg_work, register_bdev_worker);
        else
-               INIT_WORK(&args->reg_work, register_cache_worker);
+               INIT_DELAYED_WORK(&args->reg_work, register_cache_worker);
 
-       queue_work(system_wq, &args->reg_work);
+       /* 10 jiffies is enough for a delay */
+       queue_delayed_work(system_wq, &args->reg_work, 10);
 }
 
 static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,