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    Subject[PATCH] Cache alias issues for swapped page
    Date
    For SH-4 (with virtually indexed, physically tagged cache), we have
    problems with swap.

    I think that there're bugs in do_swap_page and try_to_swap_out.
    I've read "Documentation/cachetlb.txt" and I know that now is
    the transition to newer interface, but we need a fix at the moment
    with old interface.

    (1) Flush is needed at do_swap_page

    With current implementation, cache is flushed when it is swapped in
    synchronously. When it is swapped in asynchronously
    (swapfile.c:try_to_unuse, memory.c:swapin_readahead), there's no
    flushing which causes alias.

    (2) Flush is needed at try_to_swap

    When swap out, flushing is needed for physical tag too.

    Here's a patch to indicate the issues.

    diff -ruN linux-2.4.0-test8-pre6/mm/memory.c linux/mm/memory.c
    --- linux-2.4.0-test8-pre6/mm/memory.c Thu Sep 7 09:56:19 2000
    +++ linux/mm/memory.c Mon Sep 4 15:25:17 2000
    @@ -1068,9 +1068,6 @@
    unlock_kernel();
    if (!page)
    return -1;
    -
    - flush_page_to_ram(page);
    - flush_icache_page(vma, page);
    }

    mm->rss++;
    @@ -1093,6 +1090,8 @@
    } else
    UnlockPage(page);

    + flush_page_to_ram(page);
    + flush_icache_page(vma, page);
    set_pte(page_table, pte);
    /* No need to invalidate - it was non-present before */
    update_mmu_cache(vma, address, pte);
    diff -ruN linux-2.4.0-test8-pre6/mm/vmscan.c linux/mm/vmscan.c
    --- linux-2.4.0-test8-pre6/mm/vmscan.c Thu Sep 7 09:56:19 2000
    +++ linux/mm/vmscan.c Mon Sep 4 15:25:18 2000
    @@ -138,6 +138,7 @@
    *
    * That would get rid of a lot of problems.
    */
    + flush_page_to_ram(page);
    flush_cache_page(vma, address);
    if (vma->vm_ops && (swapout = vma->vm_ops->swapout)) {
    int error;
    --
    -
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