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    SubjectRe: [PATCH -next 2/5] mm/kmemleak: skip update_checksum for OBJECT_NO_SCAN objects
    On Mon, Sep 21, 2020 at 02:00:04AM +0000, Chen Jun wrote:
    > From: Wei Yongjun <weiyongjun1@huawei.com>
    >
    > Objects marked with OBJECT_NO_SCAN are never scanned.
    > So there is no need to update checksum for them.
    >
    > Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
    > Signed-off-by: Chen Jun <chenjun102@huawei.com>
    > ---
    > mm/kmemleak.c | 4 ++++
    > 1 file changed, 4 insertions(+)
    >
    > diff --git a/mm/kmemleak.c b/mm/kmemleak.c
    > index b3f603fd9fc3..c09c6b59eda6 100644
    > --- a/mm/kmemleak.c
    > +++ b/mm/kmemleak.c
    > @@ -1166,6 +1166,10 @@ static bool update_checksum(struct kmemleak_object *object)
    > {
    > u32 old_csum = object->checksum;
    >
    > + /* always return false for not scan object */
    > + if (object->flags & OBJECT_NO_SCAN)
    > + return false;

    The reason for OBJECT_NO_SCAN is to avoid introducing more false
    negatives. The point of the checksum is to reduce the false positives -
    i.e. an object that is being modified between scans won't be considered
    a (transient) leak even if kmemleak couldn't find a reference pointer to
    it.

    So please drop this patch.

    --
    Catalin

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