[PATCH] raid5: fix to detect failure of register_shrinker

[PATCH] raid5: fix to detect failure of register_shrinker

[Chao Yu]

register_shrinker can fail after commit 1d3d4437eae1 ("vmscan: per-node
deferred work"), we should detect the failure of it, otherwise we may
fail to register shrinker after raid5 configuration was setup successfully.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
 drivers/md/raid5.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 766c3b7..b819a9a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6632,7 +6632,12 @@ static struct r5conf *setup_conf(struct mddev *mddev)
 	conf->shrinker.count_objects = raid5_cache_count;
 	conf->shrinker.batch = 128;
 	conf->shrinker.flags = 0;
-	register_shrinker(&conf->shrinker);
+	if (register_shrinker(&conf->shrinker)) {
+		printk(KERN_ERR
+		       "md/raid:%s: couldn't register shrinker.\n",
+		       mdname(mddev));
+		goto abort;
+	}
 
 	sprintf(pers_name, "raid%d", mddev->new_level);
 	conf->thread = md_register_thread(raid5d, mddev, pers_name);
-- 
2.7.2

Re: [PATCH] raid5: fix to detect failure of register_shrinker

[Shaohua Li]

On Tue, Sep 20, 2016 at 10:33:57AM +0800, Chao Yu wrote:
> register_shrinker can fail after commit 1d3d4437eae1 ("vmscan: per-node
> deferred work"), we should detect the failure of it, otherwise we may
> fail to register shrinker after raid5 configuration was setup successfully.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  drivers/md/raid5.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 766c3b7..b819a9a 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -6632,7 +6632,12 @@ static struct r5conf *setup_conf(struct mddev *mddev)
>  	conf->shrinker.count_objects = raid5_cache_count;
>  	conf->shrinker.batch = 128;
>  	conf->shrinker.flags = 0;
> -	register_shrinker(&conf->shrinker);
> +	if (register_shrinker(&conf->shrinker)) {
> +		printk(KERN_ERR
> +		       "md/raid:%s: couldn't register shrinker.\n",
> +		       mdname(mddev));
> +		goto abort;
> +	}
>  
>  	sprintf(pers_name, "raid%d", mddev->new_level);
>  	conf->thread = md_register_thread(raid5d, mddev, pers_name);

shrinker isn't fatal for raid5. Idealy we can ignore the error and stop
automatically stripe cache increase, but probable it's not worthy the effort.
Applied the patch.

Also the free_conf need better way to check if shrinker register successes. I
add another patch to fix it.

Thanks,
Shaohua