linux-kernel - Re: [PATCH v14 02/12] powerpc/irq: use memblock functions returning virtual address

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Date:   Thu, 24 Jan 2019 16:51:53 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v14 02/12] powerpc/irq: use memblock functions returning
 virtual address

On Thu, Jan 24, 2019 at 04:19:33PM +0000, Christophe Leroy wrote:
> Since only the virtual address of allocated blocks is used,
> lets use functions returning directly virtual address.
> 
> Those functions have the advantage of also zeroing the block.
> 
> Suggested-by: Mike Rapoport <rppt@...ux.ibm.com>
> Acked-by: Mike Rapoport <rppt@...ux.ibm.com>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

[...]

> +static void *__init alloc_stack(void)
> +{
> +	void *ptr = memblock_alloc(THREAD_SIZE, THREAD_SIZE);
> +
> +	if (!ptr)
> +		panic("cannot allocate stacks");
> +
> +	return ptr;
> +}

I believe memblock_alloc() will panic() if it cannot allocate memory,
since that goes:

 memblock_alloc()
 -> memblock_alloc_try_nid()
    -> panic()

So you can get rid of the panic() here, or if you want a custom panic
message, you can use memblock_alloc_nopanic().

[...]

>  static void *__init alloc_stack(unsigned long limit, int cpu)
>  {
> -	unsigned long pa;
> +	void *ptr;
>  
>  	BUILD_BUG_ON(STACK_INT_FRAME_SIZE % 16);
>  
> -	pa = memblock_alloc_base_nid(THREAD_SIZE, THREAD_SIZE, limit,
> -					early_cpu_to_node(cpu), MEMBLOCK_NONE);
> -	if (!pa) {
> -		pa = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit);
> -		if (!pa)
> -			panic("cannot allocate stacks");
> -	}
> +	ptr = memblock_alloc_try_nid(THREAD_SIZE, THREAD_SIZE,
> +				     MEMBLOCK_LOW_LIMIT, limit,
> +				     early_cpu_to_node(cpu));
> +	if (!ptr)
> +		panic("cannot allocate stacks");

The same applies here -- memblock_alloc_try_nid() will panic itself
rather than returning NULL.

Otherwise, this looks like a nice cleanup. With the panics removed (or
using the _nopanic() allocators), feel free to add:

Acked-by: Mark Rutland <mark.rutland@....com>

Thanks,
Mark.