4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Li Wang <[email protected]> [ Upstream commit 16e536ef47f567289a5699abee9ff7bb304bc12d ] /sys/../zswap/stored_pages keeps rising in a zswap test with "zswap.max_pool_percent=0" parameter. But it should not compress or store pages any more since there is no space in the compressed pool. Reproduce steps: 1. Boot kernel with "zswap.enabled=1" 2. Set the max_pool_percent to 0 # echo 0 > /sys/module/zswap/parameters/max_pool_percent 3. Do memory stress test to see if some pages have been compressed # stress --vm 1 --vm-bytes $mem_available"M" --timeout 60s 4. Watching the 'stored_pages' number increasing or not The root cause is: When zswap_max_pool_percent is set to 0 via kernel parameter, zswap_is_full() will always return true due to zswap_shrink(). But if the shinking is able to reclain a page successfully the code then proceeds to compressing/storing another page, so the value of stored_pages will keep changing. To solve the issue, this patch adds a zswap_is_full() check again after zswap_shrink() to make sure it's now under the max_pool_percent, and to not compress/store if we reached the limit. Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Li Wang <[email protected]> Acked-by: Dan Streetman <[email protected]> Cc: Seth Jennings <[email protected]> Cc: Huang Ying <[email protected]> Cc: Yu Zhao <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/zswap.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1018,6 +1018,15 @@ static int zswap_frontswap_store(unsigne ret = -ENOMEM; goto reject; } + + /* A second zswap_is_full() check after + * zswap_shrink() to make sure it's now + * under the max_pool_percent + */ + if (zswap_is_full()) { + ret = -ENOMEM; + goto reject; + } } /* allocate entry */
