Commit 0a477e1a authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
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kernel/sysctl: support handling command line aliases 



We can now handle sysctl parameters on kernel command line, but
historically some parameters introduced their own command line
equivalent, which we don't want to remove for compatibility reasons.

We can, however, convert them to the generic infrastructure with a table
translating the legacy command line parameters to their sysctl names,
and removing the one-off param handlers.

This patch adds the support and makes the first conversion to
demonstrate it, on the (deprecated) numa_zonelist_order parameter.

Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Guilherme G . Piccoli" <gpiccoli@canonical.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Ivan Teterevkov <ivan.teterevkov@nutanix.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200427180433.7029-3-vbabka@suse.cz


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3db978d4

fs/proc/proc_sysctl.c

+41 −7
Original line number Diff line number Diff line
@@ -1705,6 +1705,37 @@ int __init proc_sys_init(void) 
	return sysctl_init();

}



struct sysctl_alias {

	const char *kernel_param;

	const char *sysctl_param;

};



/*

 * Historically some settings had both sysctl and a command line parameter.

 * With the generic sysctl. parameter support, we can handle them at a single

 * place and only keep the historical name for compatibility. This is not meant

 * to add brand new aliases. When adding existing aliases, consider whether

 * the possibly different moment of changing the value (e.g. from early_param

 * to the moment do_sysctl_args() is called) is an issue for the specific

 * parameter.

 */

static const struct sysctl_alias sysctl_aliases[] = {

	{"numa_zonelist_order",		"vm.numa_zonelist_order" },

	{ }

};



static const char *sysctl_find_alias(char *param)

{

	const struct sysctl_alias *alias;



	for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) {

		if (strcmp(alias->kernel_param, param) == 0)

			return alias->sysctl_param;

	}



	return NULL;

}



/* Set sysctl value passed on kernel command line. */

static int process_sysctl_arg(char *param, char *val,

			       const char *unused, void *arg)
@@ -1718,15 +1749,18 @@ static int process_sysctl_arg(char *param, char *val, 
	loff_t pos = 0;

	ssize_t wret;



	if (strncmp(param, "sysctl", sizeof("sysctl") - 1))

		return 0;



	if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {

		param += sizeof("sysctl") - 1;



		if (param[0] != '/' && param[0] != '.')

			return 0;



		param++;

	} else {

		param = (char *) sysctl_find_alias(param);

		if (!param)

			return 0;

	}



	/*

	 * To set sysctl options, we use a temporary mount of proc, look up the

mm/page_alloc.c

+0 −9
Original line number Diff line number Diff line
@@ -5575,15 +5575,6 @@ static int __parse_numa_zonelist_order(char *s) 
	return 0;

}



static __init int setup_numa_zonelist_order(char *s)

{

	if (!s)

		return 0;



	return __parse_numa_zonelist_order(s);

}

early_param("numa_zonelist_order", setup_numa_zonelist_order);



char numa_zonelist_order[] = "Node";



/*

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