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From: Vlastimil Babka <vbabka@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Iurii Zaikin <yzaikin@google.com>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	linux-mm@kvack.org, Ivan Teterevkov <ivan.teterevkov@nutanix.com>,
	Michal Hocko <mhocko@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"Guilherme G . Piccoli" <gpiccoli@canonical.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@suse.com>
Subject: [PATCH v3 2/5] kernel/sysctl: support handling command line aliases
Date: Mon, 27 Apr 2020 20:04:30 +0200	[thread overview]
Message-ID: <20200427180433.7029-3-vbabka@suse.cz> (raw)
In-Reply-To: <20200427180433.7029-1-vbabka@suse.cz>

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: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 fs/proc/proc_sysctl.c | 48 ++++++++++++++++++++++++++++++++++++-------
 mm/page_alloc.c       |  9 --------
 2 files changed, 41 insertions(+), 16 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 7804da5f5be0..209ad03e1b82 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1694,6 +1694,37 @@ 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)
@@ -1707,15 +1738,18 @@ 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;
-
-	param += sizeof("sysctl") - 1;
+	if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
+		param += sizeof("sysctl") - 1;
 
-	if (param[0] != '/' && param[0] != '.')
-		return 0;
+		if (param[0] != '/' && param[0] != '.')
+			return 0;
 
-	param++;
+		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
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 69827d4fa052..80b2788711c9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5531,15 +5531,6 @@ 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";
 
 /*
-- 
2.26.0


  parent reply	other threads:[~2020-04-27 18:05 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-27 18:04 [PATCH v3 0/5] support setting sysctl parameters from kernel command line Vlastimil Babka
2020-04-27 18:04 ` [PATCH v3 1/5] kernel/sysctl: " Vlastimil Babka
2020-04-27 18:33   ` Andrew Morton
2020-04-28  8:09     ` Vlastimil Babka
2020-04-28 10:18       ` Michal Hocko
2020-04-27 18:04 ` Vlastimil Babka [this message]
2020-04-27 18:04 ` [PATCH v3 3/5] kernel/hung_task convert hung_task_panic boot parameter to sysctl Vlastimil Babka
2020-04-27 18:04 ` [PATCH v3 4/5] tools/testing/selftests/sysctl/sysctl.sh: support CONFIG_TEST_SYSCTL=y Vlastimil Babka
2020-04-27 18:39   ` Luis Chamberlain
2020-04-27 18:04 ` [PATCH v3 5/5] lib/test_sysctl: support testing of sysctl. boot parameter Vlastimil Babka
2020-04-27 18:39   ` Luis Chamberlain
2020-05-11 11:05     ` Vlastimil Babka
2020-05-11 18:31       ` Luis Chamberlain
2020-05-13  8:58         ` Vlastimil Babka
2020-05-13 13:15           ` Luis Chamberlain
2020-05-13 13:17             ` Luis Chamberlain
2020-05-13 13:17               ` Luis Chamberlain
2020-05-15 16:02               ` Vlastimil Babka

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