linux-kernel - Re: [PATCH 1/3] mm/zsmalloc: avoid unregister a NOT-registered zsmalloc zpool driver

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Message-ID: <20141113152247.GB1408@swordfish>
Date:	Fri, 14 Nov 2014 00:22:48 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Mahendran Ganesh <opensource.ganesh@...il.com>
Cc:	minchan@...nel.org, ngupta@...are.org, ddstreet@...e.org,
	sergey.senozhatsky@...il.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm/zsmalloc: avoid unregister a NOT-registered
 zsmalloc zpool driver

On (11/13/14 21:37), Mahendran Ganesh wrote:
> Now zsmalloc can be registered as a zpool driver into zpool when
> CONFIG_ZPOOL is enabled. During the init of zsmalloc, when error happens,
> we need to do cleanup. But in current code, it will unregister a not yet
> registered zsmalloc zpool driver(*zs_zpool_driver*).
> 
> This patch puts the cleanup in zs_init() instead of calling zs_exit()
> where it will unregister a not-registered zpool driver.
> 
> Signed-off-by: Mahendran Ganesh <opensource.ganesh@...il.com>
> ---
>  mm/zsmalloc.c |   12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 839a48c..3d2bb36 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -907,10 +907,8 @@ static int zs_init(void)
>  	__register_cpu_notifier(&zs_cpu_nb);
>  	for_each_online_cpu(cpu) {
>  		ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
> -		if (notifier_to_errno(ret)) {
> -			cpu_notifier_register_done();
> +		if (notifier_to_errno(ret))
>  			goto fail;
> -		}
>  	}
>  
>  	cpu_notifier_register_done();
> @@ -920,8 +918,14 @@ static int zs_init(void)
>  #endif
>  
>  	return 0;
> +
>  fail:
> -	zs_exit();
> +	for_each_online_cpu(cpu)
> +		zs_cpu_notifier(NULL, CPU_UP_CANCELED, (void *)(long)cpu);
> +	__unregister_cpu_notifier(&zs_cpu_nb);
> +
> +	cpu_notifier_register_done();
> +
>  	return notifier_to_errno(ret);

so we duplicate same code, and there is a bit confusing part
now: zs_cpu_notifier(CPU_UP_CANCELED) and zs_cpu_notifier(CPU_DEAD)
calls.


how about something like this?

Factor out zsmalloc cpu notifier unregistration code and call
it from both zs_exit() and zs_init() error path.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

---

 mm/zsmalloc.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index b3b57ef..c4d2d60 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -881,14 +881,10 @@ static struct notifier_block zs_cpu_nb = {
 	.notifier_call = zs_cpu_notifier
 };
 
-static void zs_exit(void)
+static inline void zs_unregister_cpu_notifier()
 {
 	int cpu;
 
-#ifdef CONFIG_ZPOOL
-	zpool_unregister_driver(&zs_zpool_driver);
-#endif
-
 	cpu_notifier_register_begin();
 
 	for_each_online_cpu(cpu)
@@ -898,6 +894,14 @@ static void zs_exit(void)
 	cpu_notifier_register_done();
 }
 
+static void zs_exit(void)
+{
+#ifdef CONFIG_ZPOOL
+	zpool_unregister_driver(&zs_zpool_driver);
+#endif
+	zs_unregister_cpu_notifier();
+}
+
 static int zs_init(void)
 {
 	int cpu, ret;
@@ -907,10 +911,8 @@ static int zs_init(void)
 	__register_cpu_notifier(&zs_cpu_nb);
 	for_each_online_cpu(cpu) {
 		ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
-		if (notifier_to_errno(ret)) {
-			cpu_notifier_register_done();
+		if (notifier_to_errno(ret))
 			goto fail;
-		}
 	}
 
 	cpu_notifier_register_done();
@@ -921,7 +923,7 @@ static int zs_init(void)
 
 	return 0;
 fail:
-	zs_exit();
+	zs_unregister_cpu_notifier();
 	return notifier_to_errno(ret);
 }
 
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