The '/sys/../zswap/stored_pages:' keep raising in zswap test with
"zswap.max_pool_percent=0" parameter. But theoretically, it should
not compress or store pages any more since there is no space for
compressed pool.
Reproduce steps:
1. Boot kernel with "zswap.enabled=1 zswap.max_pool_percent=17"
2. Set the max_pool_percent to 0
# echo 0 > /sys/module/zswap/parameters/max_pool_percent
Confirm this parameter works fine
# cat /sys/kernel/debug/zswap/pool_total_size
0
3. Do memory stress test to see if some pages have been compressed
# stress --vm 1 --vm-bytes $mem_available"M" --timeout 60s
Watching the 'stored_pages' numbers increasing or not
The root cause is:
When the zswap_max_pool_percent is set to 0 via kernel parameter, the zswap_is_full()
will always return true to shrink the pool size by zswap_shrink(). If the pool size
has been shrinked a little success, zswap will do compress/store pages again. Then we
get fails on that as above.
Signed-off-by: Li Wang <liwang@xxxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Huang Ying <huang.ying.caritas@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
---
mm/zswap.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/mm/zswap.c b/mm/zswap.c
index 61a5c41..2b537bb 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1007,6 +1007,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
u8 *src, *dst;
struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
+ if (!zswap_max_pool_percent) {
+ ret = -ENOMEM;
+ goto reject;
+ }
+
/* THP isn't supported */
if (PageTransHuge(page)) {
ret = -EINVAL;
--
2.9.5
