path: root/mm
diff options
authorLi Wang <>2018-07-26 16:37:42 -0700
committerLinus Torvalds <>2018-07-26 19:38:03 -0700
commit16e536ef47f567289a5699abee9ff7bb304bc12d (patch)
tree90e8f576c068c6f24dcda02dfc367b8eef0577d4 /mm
parentfa3fc2ad99b4f025446d1cff589a8d2dd7db92f2 (diff)
zswap: re-check zswap_is_full() after do zswap_shrink()
/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: Signed-off-by: Li Wang <> Acked-by: Dan Streetman <> Cc: Seth Jennings <> Cc: Huang Ying <> Cc: Yu Zhao <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm')
1 files changed, 9 insertions, 0 deletions
diff --git a/mm/zswap.c b/mm/zswap.c
index 7d34e69507e3..cd91fd9d96b8 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1026,6 +1026,15 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
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 */