• Hugh Dickins's avatar
    mm: fix swapops.h:131 bug if remap_file_pages raced migration · 7e09e738
    Hugh Dickins authored
    Add remove_linear_migration_ptes_from_nonlinear(), to fix an interesting
    little include/linux/swapops.h:131 BUG_ON(!PageLocked) found by trinity:
    indicating that remove_migration_ptes() failed to find one of the
    migration entries that was temporarily inserted.
    
    The problem comes from remap_file_pages()'s switch from vma_interval_tree
    (good for inserting the migration entry) to i_mmap_nonlinear list (no good
    for locating it again); but can only be a problem if the remap_file_pages()
    range does not cover the whole of the vma (zap_pte() clears the range).
    
    remove_migration_ptes() needs a file_nonlinear method to go down the
    i_mmap_nonlinear list, applying linear location to look for migration
    entries in those vmas too, just in case there was this race.
    
    The file_nonlinear method does need rmap_walk_control.arg to do this;
    but it never needed vma passed in - vma comes from its own iteration.
    Reported-and-tested-by: default avatarDave Jones <davej@redhat.com>
    Reported-and-tested-by: default avatarSasha Levin <sasha.levin@oracle.com>
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    7e09e738
migrate.c 49 KB