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    Subject[PATCH] swapin flush cache bug

    Hi,

    Niibe Yutaka noted (and added an entry on the MM bugzilla system) that
    cache flushing on do_swap_page() is buggy. Here:

    ---
    struct page *page = lookup_swap_cache(entry);
    pte_t pte;

    if (!page) {
    lock_kernel();
    swapin_readahead(entry);
    page = read_swap_cache(entry);
    unlock_kernel();
    if (!page)
    return -1;

    flush_page_to_ram(page);
    flush_icache_page(vma, page);
    }

    mm->rss++;
    --

    If lookup_swap_cache() finds a page in the swap cache, and that page was
    in memory because of the swapin readahead, the cache is not flushed.

    Here is a patch to fix the problem by always flushing the cache including
    for pages in the swap cache:

    --- linux.orig/mm/memory.c.orig Thu Feb 8 10:52:20 2001
    +++ linux/mm/memory.c Thu Feb 8 10:54:07 2001
    @@ -1033,12 +1033,12 @@
    unlock_kernel();
    if (!page)
    return -1;
    -
    - flush_page_to_ram(page);
    - flush_icache_page(vma, page);
    }

    mm->rss++;
    +
    + flush_page_to_ram(page);
    + flush_icache_page(vma, page);

    pte = mk_pte(page, vma->vm_page_prot);



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