• Hugh Dickins's avatar
    tmpfs: convert shmem_writepage and enable swap · 6922c0c7
    Hugh Dickins authored
    Convert shmem_writepage() to use shmem_delete_from_page_cache() to use
    shmem_radix_tree_replace() to substitute swap entry for page pointer
    atomically in the radix tree.
    As with shmem_add_to_page_cache(), it's not entirely satisfactory to be
    copying such code from delete_from_swap_cache, but again judged easier
    to sell than making its other callers go through the extras.
    Remove the toy implementation's shmem_put_swap() and shmem_get_swap(),
    now unreferenced, and the hack to disable swap: it's now good to go.
    The way things have worked out, info->lock no longer helps to guard the
    shmem_swaplist: we increment swapped under shmem_swaplist_mutex only.
    That global mutex exclusion between shmem_writepage() and shmem_unuse()
    is not pretty, and we ought to find another way; but it's been forced on
    us by recent race discoveries, not a consequence of this patchset.
    And what has become of the WARN_ON_ONCE(1) free_swap_and_cache() if a
    swap entry was found already present? That's no longer possible, the
    (unknown) one inserting this page into filecache would hit the swap
    entry occupying that slot.
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Acked-by: default avatarRik van Riel <riel@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
shmem.c 64.2 KB