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Date: Sat, 16 Oct 2010 14:10:19 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Ted Ts'o" <tytso@mit.edu>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: jbd2: Convert jbd2_slab_create_sem to mutex
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On Sat, 16 Oct 2010 22:34:39 +0200 (CEST) Thomas Gleixner <tglx@linutronix.de> wrote:

> jbd2_slab_create_sem is used as a mutex, so make it one.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>  fs/jbd2/journal.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> Index: linux-next/fs/jbd2/journal.c
> ===================================================================
> --- linux-next.orig/fs/jbd2/journal.c
> +++ linux-next/fs/jbd2/journal.c
> @@ -1838,7 +1838,7 @@ size_t journal_tag_bytes(journal_t *jour
>   */
>  #define JBD2_MAX_SLABS 8
>  static struct kmem_cache *jbd2_slab[JBD2_MAX_SLABS];
> -static DECLARE_MUTEX(jbd2_slab_create_sem);
> +static DEFINE_MUTEX(jbd2_slab_create_mutex);
>  
>  static const char *jbd2_slab_names[JBD2_MAX_SLABS] = {
>  	"jbd2_1k", "jbd2_2k", "jbd2_4k", "jbd2_8k",
> @@ -1870,16 +1870,16 @@ static int jbd2_journal_create_slab(size
>  
>  	if (unlikely(i < 0))
>  		i = 0;
> -	down(&jbd2_slab_create_sem);
> +	mutex_lock(&jbd2_slab_create_mutex);
>  	if (jbd2_slab[i]) {
> -		up(&jbd2_slab_create_sem);
> +		mutex_unlock(&jbd2_slab_create_mutex);
>  		return 0;	/* Already created */
>  	}
>  
>  	slab_size = 1 << (i+10);
>  	jbd2_slab[i] = kmem_cache_create(jbd2_slab_names[i], slab_size,
>  					 slab_size, 0, NULL);
> -	up(&jbd2_slab_create_sem);
> +	mutex_unlock(&jbd2_slab_create_mutex);
>  	if (!jbd2_slab[i]) {
>  		printk(KERN_EMERG "JBD2: no memory for jbd2_slab cache\n");
>  		return -ENOMEM;

gad, whodidthat.

We may as well make it local to jbd2_journal_create_slab() also.