memsw: handle swapaccount kernel parameter correctly

__setup based kernel command line parameters handlers which are handled in
obsolete_checksetup are provided with the parameter value including =
(more precisely everything right after the parameter name).

This means that the current implementation of swapaccount[=1|0] doesn't
work at all because if there is a value for the parameter then we are
testing for "0" resp.  "1" but we are getting "=0" resp.  "=1" and if
there is no parameter value we are getting an empty string rather than
NULL.

The original noswapccount parameter, which doesn't care about the value,
works correctly.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3878cfe399dc8733bbc0633aa248b3f4dea231f0..44f9f9c89f0c7c8b706fd87118932b512977e9a3 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5024,9 +5024,9 @@ struct cgroup_subsys mem_cgroup_subsys = {
 static int __init enable_swap_account(char *s)
 {
        /* consider enabled if no parameter or 1 is given */
-       if (!s || !strcmp(s, "1"))
+       if (!(*s) || !strcmp(s, "=1"))
                really_do_swap_account = 1;
-       else if (!strcmp(s, "0"))
+       else if (!strcmp(s, "=0"))
                really_do_swap_account = 0;
        return 1;
 }
@@ -5034,7 +5034,7 @@ __setup("swapaccount", enable_swap_account);
 
 static int __init disable_swap_account(char *s)
 {
-       enable_swap_account("0");
+       enable_swap_account("=0");
        return 1;
 }
 __setup("noswapaccount", disable_swap_account);