[v2 2/2] mm: khugepaged: avoid overriding min_free_kbytes set by user

Vijay Balakrishna
2020-09-15T21:14:58Z

set_recommended_min_free_kbytes need to honor min_free_kbytes set by the
user. Post start-of-day THP enable or memory hotplug operations can
lose user specified min_free_kbytes, in particular when it is higher than
calculated recommended value. Also modifying "recommended_min" variable
type to "int" from "unsigned long" to avoid undesired result noticed
during testing. It is due to comparing "unsigned long" with "int" type.

Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: stable@vger.kernel.org
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
---
mm/khugepaged.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 4f7107476a6f..b4b753ba411a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2253,7 +2253,7 @@ static void set_recommended_min_free_kbytes(void)
{
struct zone *zone;
int nr_zones = 0;
- unsigned long recommended_min;
+ int recommended_min;

for_each_populated_zone(zone) {
/*
@@ -2280,12 +2280,12 @@ static void set_recommended_min_free_kbytes(void)

/* don't ever allow to reserve more than 5% of the lowmem */
recommended_min = min(recommended_min,
- (unsigned long) nr_free_buffer_pages() / 20);
+ (int) nr_free_buffer_pages() / 20);
recommended_min <<= (PAGE_SHIFT-10);

- if (recommended_min > min_free_kbytes) {
+ if (recommended_min > user_min_free_kbytes) {
if (user_min_free_kbytes >= 0)
- pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
+ pr_info("raising min_free_kbytes from %d to %d to help transparent hugepage allocations\n",
min_free_kbytes, recommended_min);

min_free_kbytes = recommended_min;
--
2.28.0