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Re: [PATCHv3 1/8] powerpc/vdso: unify return paths in setup_additional_pages

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Hi Dmitry,

Thanks for the patches.

Dmitry Safonov <dsafonov@virtuozzo.com> writes:
> Impact: cleanup

I'm not a fan of these "Impact" lines, especially when they're not
correct, ie. this is not a cleanup, a cleanup doesn't change logic.

> Rename `rc' variable which doesn't seems to mean anything into
> kernel-known `ret'.

'rc' means "Return Code", it's fairly common. I see at least ~8500
"int rc" declarations in the kernel.

Please don't rename variables and change logic in one patch.

> Combine two function returns into one as it's
> also easier to read.
>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-mm@kvack.org
> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
> ---
>  arch/powerpc/kernel/vdso.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
> index 4111d30badfa..4ffb82a2d9e9 100644
> --- a/arch/powerpc/kernel/vdso.c
> +++ b/arch/powerpc/kernel/vdso.c
> @@ -154,7 +154,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>  	struct page **vdso_pagelist;
>  	unsigned long vdso_pages;
>  	unsigned long vdso_base;
> -	int rc;
> +	int ret = 0;
  
Please don't initialise return codes in the declaration, it prevents the
compiler from warning you if you forget to initialise it in a
particular path.

AFAICS you never even use the default value either.

>  	if (!vdso_ready)
>  		return 0;
> @@ -203,8 +203,8 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>  				      ((VDSO_ALIGNMENT - 1) & PAGE_MASK),
>  				      0, 0);
>  	if (IS_ERR_VALUE(vdso_base)) {
> -		rc = vdso_base;
> -		goto fail_mmapsem;
> +		ret = vdso_base;
> +		goto out_up_mmap_sem;
>  	}
>  
>  	/* Add required alignment. */
> @@ -227,21 +227,16 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>  	 * It's fine to use that for setting breakpoints in the vDSO code
>  	 * pages though.
>  	 */
> -	rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
> +	ret = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
>  				     VM_READ|VM_EXEC|
>  				     VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
>  				     vdso_pagelist);
> -	if (rc) {
> +	if (ret)
>  		current->mm->context.vdso_base = 0;
> -		goto fail_mmapsem;
> -	}
> -
> -	up_write(&mm->mmap_sem);
> -	return 0;
>  
> - fail_mmapsem:
> +out_up_mmap_sem:
>  	up_write(&mm->mmap_sem);
> -	return rc;
> +	return ret;
>  }


If you strip out the variable renames then I think that change would be
OK.

cheers

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Re: [PATCHv3 1/8] powerpc/vdso: unify return paths in setup_additional_pages Michael Ellerman <mpe@ellerman.id.au> - 2016-11-08 01:20 +0100

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