• Johannes Weiner's avatar
    mm: memcontrol: charge swapin pages on instantiation · 4c6355b2
    Johannes Weiner authored
    Right now, users that are otherwise memory controlled can easily escape
    their containment and allocate significant amounts of memory that they're
    not being charged for.  That's because swap readahead pages are not being
    charged until somebody actually faults them into their page table.  This
    can be exploited with MADV_WILLNEED, which triggers arbitrary readahead
    allocations without charging the pages.
    
    There are additional problems with the delayed charging of swap pages:
    
    1. To implement refault/workingset detection for anonymous pages, we
       need to have a target LRU available at swapin time, but the LRU is not
       determinable until the page has been charged.
    
    2. To implement per-cgroup LRU locking, we need page->mem_cgroup to be
       stable when the page is isolated from the LRU; otherwise, the locks
       change under us.  But swapcache gets charged after it's already on the
       LRU, and even if we cannot isolate it ourselves (since charging is not
       exactly optional).
    
    The previous patch ensured we always maintain cgroup ownership records for
    swap pages.  This patch moves the swapcache charging point from the fault
    handler to swapin time to fix all of the above problems.
    
    v2: simplify swapin error checking (Joonsoo)
    
    [hughd@google.com: fix livelock in __read_swap_cache_async()]
      Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2005212246080.8458@eggly.anvilsSigned-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Reviewed-by: default avatarAlex Shi <alex.shi@linux.alibaba.com>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Roman Gushchin <guro@fb.com>
    Cc: Shakeel Butt <shakeelb@google.com>
    Cc: Balbir Singh <bsingharora@gmail.com>
    Cc: Rafael Aquini <aquini@redhat.com>
    Cc: Alex Shi <alex.shi@linux.alibaba.com>
    Link: http://lkml.kernel.org/r/20200508183105.225460-17-hannes@cmpxchg.orgSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    4c6355b2
memory.c 135 KB