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Date: Thu, 04 Apr 2013 15:55:17 +0900
From: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To: Yinghai Lu <yinghai@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
"H. Peter Anvin" <hpa@...or.com>, WANG Chao <chaowang@...hat.com>,
Vivek Goyal <vgoyal@...hat.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] x86, kdump: Change crashkernel_high/low= to crashkernel=;high/low
(2013/04/04 9:38), Yinghai Lu wrote:
> Index: linux-2.6/kernel/kexec.c
> ===================================================================
> --- linux-2.6.orig/kernel/kexec.c
> +++ linux-2.6/kernel/kexec.c
> @@ -1360,7 +1360,7 @@ static int __init parse_crashkernel_simp
>
> if (*cur == '@')
> *crash_base = memparse(cur+1, &cur);
> - else if (*cur != ' ' && *cur != '\0') {
> + else if (*cur != ' ' && *cur != ';' && *cur != '\0') {
> pr_warning("crashkernel: unrecognized char\n");
> return -EINVAL;
> }
As I said below, ";high" or ";low" check should be here. It would be
enough to replace the condition *cur != ';' by strncmp(cur, ";high", 5)
|| strncmp(cur, ";low", 4).
> @@ -1368,58 +1368,108 @@ static int __init parse_crashkernel_simp
> return 0;
> }
>
> -/*
> - * That function is the entry point for command line parsing and should be
> - * called from the arch-specific code.
> - */
> +#define SUFFIX_HIGH 0
> +#define SUFFIX_LOW 1
> +#define SUFFIX_NULL 2
> +static __initdata char *suffix_tbl[] = {
> + [SUFFIX_HIGH] = ";high",
> + [SUFFIX_LOW] = ";low",
> + [SUFFIX_NULL] = NULL,
> +};
> +
> +static __init char *get_last_crashkernel(char *cmdline,
> + const char *name,
> + const char *suffix)
> +{
> + char *p = cmdline, *ck_cmdline = NULL;
> +
> + /* find crashkernel and use the last one if there are more */
Why did you choose the last one? Is there any reason you didn't choose
the first one?
Also, it's better to describe this bahaviour in
Documentations/kernel-parameter.txt.
> + p = strstr(p, name);
> + while (p) {
> + char *end_p = strchr(p, ' ');
> + char *q;
> +
> + if (!end_p)
> + end_p = p + strlen(p);
> +
> + if (!suffix) {
> + int i;
> +
> + /* skip the one with any known suffix */
> + for (i = 0; suffix_tbl[i]; i++) {
> + q = end_p - strlen(suffix_tbl[i]);
> + if (!strncmp(q, suffix_tbl[i],
> + strlen(suffix_tbl[i])))
> + goto next;
> + }
> + ck_cmdline = p;
> + } else {
> + q = end_p - strlen(suffix);
> + if (!strncmp(q, suffix, strlen(suffix)))
> + ck_cmdline = p;
> + }
It looks to me that this function does more than its name suggests. It
seems to me enough to get the last occurence of "crashkernel=<some
value>" and to leave the "<some value>" unknown for now.
The current code of yours checks if each "crashkernel=<some value>"
detected by strstr() ends with each of ";high" or ";low", but doesn't
check the formeter letters at all; e.g, "crashkernel=foobar;high" is passed.
Also, this function can be called in different contexts: from a variant
of parse_crashkernel_*(). Is it better to move this function in
reserve_crashkernel() and then pass the obtained "crashkernel=<some
value>" to a variant of parse_crashkernel_*() functions?
Thanks.
HATAYAMA, Daisuke
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