• Oscar Salvador's avatar
    mm,page_owner: fix accounting of pages when migrating · 718b1f33
    Oscar Salvador authored
    Upon migration, new allocated pages are being given the handle of the old
    pages.  This is problematic because it means that for the stack which
    allocated the old page, we will be substracting the old page + the new one
    when that page is freed, creating an accounting imbalance.
    
    There is an interest in keeping it that way, as otherwise the output will
    biased towards migration stacks should those operations occur often, but
    that is not really helpful.
    
    The link from the new page to the old stack is being performed by calling
    __update_page_owner_handle() in __folio_copy_owner().  The only thing that
    is left is to link the migrate stack to the old page, so the old page will
    be subtracted from the migrate stack, avoiding by doing so any possible
    imbalance.
    
    Link: https://lkml.kernel.org/r/20240404070702.2744-4-osalvador@suse.de
    Fixes: 217b2119 ("mm,page_owner: implement the tracking of the stacks count")
    Signed-off-by: default avatarOscar Salvador <osalvador@suse.de>
    Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Cc: Alexander Potapenko <glider@google.com>
    Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
    Cc: Andrey Konovalov <andreyknvl@gmail.com>
    Cc: Marco Elver <elver@google.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Palmer Dabbelt <palmer@dabbelt.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    718b1f33
page_owner.c 24.5 KB