• Hugh Dickins's avatar
    mm: numa: cleanup flow of transhuge page migration · 340ef390
    Hugh Dickins authored
    When correcting commit 04fa5d6a ("mm: migrate: check page_count of
    THP before migrating") Hugh Dickins noted that the control flow for
    transhuge migration was difficult to follow.  Unconditionally calling
    put_page() in numamigrate_isolate_page() made the failure paths of both
    migrate_misplaced_transhuge_page() and migrate_misplaced_page() more
    complex that they should be.  Further, he was extremely wary that an
    unlock_page() should ever happen after a put_page() even if the
    put_page() should never be the final put_page.
    
    Hugh implemented the following cleanup to simplify the path by calling
    putback_lru_page() inside numamigrate_isolate_page() if it failed to
    isolate and always calling unlock_page() within
    migrate_misplaced_transhuge_page().
    
    There is no functional change after this patch is applied but the code
    is easier to follow and unlock_page() always happens before put_page().
    
    [mgorman@suse.de: changelog only]
    Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Simon Jeons <simon.jeons@gmail.com>
    Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    340ef390
migrate.c 44.2 KB