linux-kernel - Re: [PATCH] kernel/crash: make parse_crashkernel()'s return value more indicant

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Date:   Fri, 19 Apr 2019 10:18:43 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Pingfan Liu <kernelfans@...il.com>
cc:     linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Julien Thierry <julien.thierry@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Robin Murphy <robin.murphy@....com>,
        Greg Hackmann <ghackmann@...roid.com>,
        Stefan Agner <stefan@...er.ch>,
        Johannes Weiner <hannes@...xchg.org>,
        David Hildenbrand <david@...hat.com>,
        Jens Axboe <axboe@...nel.dk>,
        Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Yangtao Li <tiny.windzz@...il.com>,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-ia64@...r.kernel.org, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org
Subject: Re: [PATCH] kernel/crash: make parse_crashkernel()'s return value
 more indicant

On Fri, 19 Apr 2019, Pingfan Liu wrote:

> At present, both return and crash_size should be checked to guarantee the
> success of parse_crashkernel().
> Simplify the way by returning negative if fail, positive if success. In
> case of failure, -EINVAL for bad syntax, -1 for the parsing results in
> crash_size=0.

I'm not entirely sure what you are trying to say here, but '-1' is not an
improvement at all. We surely are not short of proper error codes, right?

Also I don't see any positive return value > 0. So what is this about:

> --- a/arch/ia64/kernel/setup.c
> +++ b/arch/ia64/kernel/setup.c
> @@ -277,7 +277,7 @@ static void __init setup_crashkernel(unsigned long total, int *n)
>  
>  	ret = parse_crashkernel(boot_command_line, total,
>  			&size, &base);
> -	if (ret == 0 && size > 0) {
> +	if (ret >= 0) {

  ^^^^^^^^^^^^^^^^^^^^^^^^^^^  ????

>  	if (!memory_region_available(crash_base, crash_size)) {
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index 45a8d0b..0b626e2 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -376,7 +376,7 @@ static inline unsigned long fadump_calculate_reserve_size(void)
>  	 */
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  				&size, &base);
> -	if (ret == 0 && size > 0) {
> +	if (ret >= 0) {

and this ?

>  		unsigned long max_size;
>  
>  		if (fw_dump.reserve_bootvar)
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index 63f5a93..9f3e61a 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -122,7 +122,7 @@ void __init reserve_crashkernel(void)
>  	/* use common parsing */
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  			&crash_size, &crash_base);
> -	if (ret == 0 && crash_size > 0) {
> +	if (ret >= 0) {

Again.

>  		crashk_res.start = crash_base;
>  		crashk_res.end = crash_base + crash_size - 1;
>  	}
> --- a/arch/sh/kernel/machine_kexec.c
> +++ b/arch/sh/kernel/machine_kexec.c
> @@ -157,7 +157,7 @@ void __init reserve_crashkernel(void)
>  
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  			&crash_size, &crash_base);
> -	if (ret == 0 && crash_size > 0) {
> +	if (ret >= 0) {

And some more.

>  		crashk_res.start = crash_base;
>  		crashk_res.end = crash_base + crash_size - 1;
>  	}
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 3d872a5..62d07d4 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -526,11 +526,11 @@ static void __init reserve_crashkernel(void)
>  
>  	/* crashkernel=XM */
>  	ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
> -	if (ret != 0 || crash_size <= 0) {
> +	if (ret == -EINVAL) {

Without an explanation why this proceedes on error codes other than EINVAL
this is uncomprehensible. Comments exist for a reason.

>  		/* crashkernel=X,high */
>  		ret = parse_crashkernel_high(boot_command_line, total_mem,
>  					     &crash_size, &crash_base);
> -		if (ret != 0 || crash_size <= 0)
> +		if (ret < 0)
>  			return;
>  		high = true;

> @@ -87,7 +87,7 @@ static int __init parse_crashkernel_mem(char *cmdline,
>  		cur = tmp;
>  		if (size >= system_ram) {
>  			pr_warn("crashkernel: invalid size\n");
> -			return -EINVAL;
> +			return -1;

Well, this is incomprehensible as well. The pr_warn() says invalid and then
you change the error code to something magic.

Thanks,

	tglx