• Hugh Dickins's avatar
    memcg: fix split_huge_page_refcounts() · 12d27107
    Hugh Dickins authored
    This patch started off as a cleanup: __split_huge_page_refcounts() has to
    cope with two scenarios, when the hugepage being split is already on LRU,
    and when it is not; but why does it have to split that accounting across
    three different sites?  Consolidate it in lru_add_page_tail(), handling
    evictable and unevictable alike, and use standard add_page_to_lru_list()
    when accounting is needed (when the head is not yet on LRU).
    
    But a recent regression in -next, I guess the removal of PageCgroupAcctLRU
    test from mem_cgroup_split_huge_fixup(), makes this now a necessary fix:
    under load, the MEM_CGROUP_ZSTAT count was wrapping to a huge number,
    messing up reclaim calculations and causing a freeze at rmdir of cgroup.
    
    Add a VM_BUG_ON to mem_cgroup_lru_del_list() when we're about to wrap that
    count - this has not been the only such incident.  Document that
    lru_add_page_tail() is for Transparent HugePages by #ifdef around it.
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Michal Hocko <mhocko@suse.cz>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    12d27107
huge_memory.c 63.6 KB