• Vladimir Davydov's avatar
    list_lru: add helpers to isolate items · 3f97b163
    Vladimir Davydov authored
    Currently, the isolate callback passed to the list_lru_walk family of
    functions is supposed to just delete an item from the list upon returning
    LRU_REMOVED or LRU_REMOVED_RETRY, while nr_items counter is fixed by
    __list_lru_walk_one after the callback returns.  Since the callback is
    allowed to drop the lock after removing an item (it has to return
    LRU_REMOVED_RETRY then), the nr_items can be less than the actual number
    of elements on the list even if we check them under the lock.  This makes
    it difficult to move items from one list_lru_one to another, which is
    required for per-memcg list_lru reparenting - we can't just splice the
    lists, we have to move entries one by one.
    This patch therefore introduces helpers that must be used by callback
    functions to isolate items instead of raw list_del/list_move.  These are
    list_lru_isolate and list_lru_isolate_move.  They not only remove the
    entry from the list, but also fix the nr_items counter, making sure
    nr_items always reflects the actual number of elements on the list if
    checked under the appropriate lock.
    Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Michal Hocko <mhocko@suse.cz>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Pekka Enberg <penberg@kernel.org>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    Cc: Dave Chinner <david@fromorbit.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
workingset.c 13.6 KB