[PATCH 3/4] bcache: use delayed kworker fo asynchronous devices registration

colyli
2020-06-14T16:53:49Z

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>
---
drivers/md/bcache/super.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 904ea9bbb5c4..a6e79083010a 100644
--- 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 @@ static void register_cache_worker(struct work_struct *work)
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,
--
2.25.0