[PATCH RFC] mm: Use pr_warn_once() for min_free_kbytes warning

[Weilin Tong <tongweilin@linux.alibaba.com>]

When min_free_kbytes is user-configured, increasing system memory via memory
hotplug may trigger multiple recalculations of min_free_kbytes. This results
in excessive warning messages flooding the kernel log if several memory blocks
are added in a short period.

Sample dmesg output before optimization:
...
[ 1303.897214] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1303.960498] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1303.970116] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1303.979709] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1303.989254] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1303.999122] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1304.008644] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1304.018537] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1304.028054] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
[ 1304.037615] min_free_kbytes is not updated to 126529 because user defined value 1048576 is preferred
...

Replace pr_warn() with pr_warn_once() to ensure only one warning is printed,
preventing large volumes of repeated log entries and improving log readability.

Signed-off-by: Weilin Tong <tongweilin@linux.alibaba.com>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index baead29b3e67..774723150e5b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6412,7 +6412,7 @@ void calculate_min_free_kbytes(void)
 	if (new_min_free_kbytes > user_min_free_kbytes)
 		min_free_kbytes = clamp(new_min_free_kbytes, 128, 262144);
 	else
-		pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
+		pr_warn_once("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
 				new_min_free_kbytes, user_min_free_kbytes);
 
 }
-- 
2.43.7