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Message-ID: <87mvhaltl5.fsf@concordia.ellerman.id.au>
Date: Tue, 08 Nov 2016 11:10:30 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Dmitry Safonov <dsafonov@...tuozzo.com>,
linux-kernel@...r.kernel.org
Cc: Dmitry Safonov <dsafonov@...tuozzo.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Andy Lutomirski <luto@...capital.net>,
Oleg Nesterov <oleg@...hat.com>, linuxppc-dev@...ts.ozlabs.org,
linux-mm@...ck.org
Subject: Re: [PATCHv3 1/8] powerpc/vdso: unify return paths in setup_additional_pages
Hi Dmitry,
Thanks for the patches.
Dmitry Safonov <dsafonov@...tuozzo.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@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-mm@...ck.org
> Signed-off-by: Dmitry Safonov <dsafonov@...tuozzo.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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