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    Subject[PATCH 1/2] vmscan: fix initial shrinker size handling
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    Shrinker function can returns -1, it means it cannot do anything without a risk of deadlock.
    For example prune_super() do this if it cannot grab superblock refrence, even if nr_to_scan=0.
    Currenly we interpret this like ULONG_MAX size shrinker, evaluate total_scan according this,
    and next time this shrinker can get really big pressure. Let's skip such shrinkers instead.

    Also make total_scan signed, otherwise check (total_scan < 0) below never works.

    Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
    ---
    mm/vmscan.c | 9 ++++++---
    1 files changed, 6 insertions(+), 3 deletions(-)

    diff --git a/mm/vmscan.c b/mm/vmscan.c
    index 29b3612..f174561 100644
    --- a/mm/vmscan.c
    +++ b/mm/vmscan.c
    @@ -248,14 +248,18 @@ unsigned long shrink_slab(struct shrink_control *shrink,

    list_for_each_entry(shrinker, &shrinker_list, list) {
    unsigned long long delta;
    - unsigned long total_scan;
    - unsigned long max_pass;
    + long total_scan;
    + long max_pass;
    int shrink_ret = 0;
    long nr;
    long new_nr;
    long batch_size = shrinker->batch ? shrinker->batch
    : SHRINK_BATCH;

    + max_pass = do_shrinker_shrink(shrinker, shrink, 0);
    + if (max_pass <= 0)
    + continue;
    +
    /*
    * copy the current shrinker scan count into a local variable
    * and zero it so that other concurrent shrinker invocations
    @@ -266,7 +270,6 @@ unsigned long shrink_slab(struct shrink_control *shrink,
    } while (cmpxchg(&shrinker->nr, nr, 0) != nr);

    total_scan = nr;
    - max_pass = do_shrinker_shrink(shrinker, shrink, 0);
    delta = (4 * nr_pages_scanned) / shrinker->seeks;
    delta *= max_pass;
    do_div(delta, lru_pages + 1);


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