linux-kernel - Re: [RFC PATCH 1/3] kmemleak: Allow partial freeing of memory blocks

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Date:	Tue, 07 Jul 2009 10:12:13 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org
Subject: Re: [RFC PATCH 1/3] kmemleak: Allow partial freeing of memory
 blocks

On Mon, 2009-07-06 at 11:51 +0100, Catalin Marinas wrote:
> @@ -552,8 +558,29 @@ static void delete_object(unsigned long ptr)
>  	 */
>  	spin_lock_irqsave(&object->lock, flags);
>  	object->flags &= ~OBJECT_ALLOCATED;
> +	start = object->pointer;
> +	end = object->pointer + object->size;
> +	min_count = object->min_count;
>  	spin_unlock_irqrestore(&object->lock, flags);
>  	put_object(object);
> +
> +	if (!size)
> +		return;
> +
> +	/*
> +	 * Partial freeing. Just create one or two objects that may result
> +	 * from the memory block split.
> +	 */
> +	if (in_atomic())
> +		gfp_flags = GFP_ATOMIC;
> +	else
> +		gfp_flags = GFP_KERNEL;

Are you sure we can do this? There's a big fat comment on top of
in_atomic() that suggest this is not safe. Why do we need to create the
object here anyway and not in the _alloc_ paths where gfp flags are
explicitly passed?

> +
> +	if (ptr > start)
> +		create_object(start, ptr - start, min_count, gfp_flags);
> +	if (ptr + size < end)
> +		create_object(ptr + size, end - ptr - size, min_count,
> +			      gfp_flags);
>  }
>  
>  /*


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