linux-kernel - Re: [PATCH 01/10] Fix idr

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Message-Id: <20080429114425.ea0e2f62.akpm@linux-foundation.org>
Date:	Tue, 29 Apr 2008 11:44:25 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Nadia.Derbey@...l.net
Cc:	manfred@...orfullife.com, paulmck@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, efault@....de, Nadia.Derbey@...l.net
Subject: Re: [PATCH 01/10] Fix idr_remove()

On Tue, 29 Apr 2008 16:33:05 +0200
Nadia.Derbey@...l.net wrote:

> [PATCH 01/10]
> 
> This patch fixes idr_remove(): the return inside the loop makes us free only
> a single layer.
> 
> Signed-off-by: Nadia Derbey <Nadia.Derbey@...l.net>
> 
> ---
>  lib/idr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6.25-mm1/lib/idr.c
> ===================================================================
> --- linux-2.6.25-mm1.orig/lib/idr.c	2008-04-25 15:29:00.000000000 +0200
> +++ linux-2.6.25-mm1/lib/idr.c	2008-04-25 15:48:34.000000000 +0200
> @@ -385,8 +385,8 @@ void idr_remove(struct idr *idp, int id)
>  	while (idp->id_free_cnt >= IDR_FREE_MAX) {
>  		p = alloc_layer(idp);
>  		kmem_cache_free(idr_layer_cache, p);
> -		return;
>  	}
> +	return;
>  }
>  EXPORT_SYMBOL(idr_remove);

erk, ancient bug.

I _think_ the implications of this are that an idr tree will grow fatter
than it needs to be, but there is no permanent leak: idr_destroy() will
still free everything, yes?

And a consequence of the fix is that idr manipulations will now result in
more allocs and frees, but the amount of memory which a tree uses will be
less?

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