• Li Wang's avatar
    zswap: re-check zswap_is_full() after do zswap_shrink() · 16e536ef
    Li Wang authored
    /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/20180530103936.17812-1-liwang@redhat.comSigned-off-by: default avatarLi Wang <liwang@redhat.com>
    Acked-by: default avatarDan Streetman <ddstreet@ieee.org>
    Cc: Seth Jennings <sjenning@redhat.com>
    Cc: Huang Ying <huang.ying.caritas@gmail.com>
    Cc: Yu Zhao <yuzhao@google.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    16e536ef