[PATCH] mm: memcontrol: clarify swapaccount=0 deprecation warning

[Johannes Weiner]

The swapaccount deprecation warning is throwing false positives. Since
we deprecated the knob and defaulted to enabling, the only reports
we've been getting are from folks that set swapaccount=1. While this
is a nice affirmation that always-enabling was the right choice, we
certainly don't want to warn when users request the supported mode.

Only warn when disabling is requested, and clarify the warning.

Fixes: b25806dcd3d5 ("mm: memcontrol: deprecate swapaccounting=0 mode")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: "Jonas Schäfer" <jonas@xxxxxxxxxxxxx>
Reported-by: Narcis Garcia <debianlists@xxxxxxxxx>
Suggested-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
 mm/memcontrol.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1ed40f9d3a27..107ec5d36819 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7971,9 +7971,13 @@ bool mem_cgroup_swap_full(struct folio *folio)
 
 static int __init setup_swap_account(char *s)
 {
-	pr_warn_once("The swapaccount= commandline option is deprecated. "
-		     "Please report your usecase to linux-mm@xxxxxxxxx if you "
-		     "depend on this functionality.\n");
+	bool res;
+
+	if (!kstrtobool(s, &res) && !res)
+		pr_warn_once("The swapaccount=0 commdandline option is deprecated "
+			     "in favor of configuring swap control via cgroupfs. "
+			     "Please report your usecase to linux-mm@xxxxxxxxx if you "
+			     "depend on this functionality.\n");
 	return 1;
 }
 __setup("swapaccount=", setup_swap_account);
-- 
2.43.0