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    SubjectRe: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3
    On Thu, May 28, 2009 at 06:51:03PM +0800, Andi Kleen wrote:
    > On Thu, May 28, 2009 at 06:33:00PM +0800, Wu Fengguang wrote:
    > > > > > You haven't waited on writeback here AFAIKS, and have you
    > > > > > *really* verified it is safe to call delete_from_swap_cache?
    > > > >
    > > > > Good catch. I'll soon submit patches for handling the under
    > > > > read/write IO pages. In this patchset they are simply ignored.
    > > >
    > > > Yes, we assume the IO device does something sensible with the poisoned
    > > > cache lines and aborts. Later we can likely abort IO requests in a early
    > > > stage on the Linux, but that's more advanced.
    > > >
    > > > The question is if we need to wait on writeback for correctness?
    > >
    > > Not necessary. Because I'm going to add a me_writeback() handler.
    >
    > Ok but without it. Let's assume me_writeback() is in the future.
    >
    > I'm mainly interested in correctness (as in not crashing) of this
    > version now.

    OK. But I suspect it doesn't matter whether to wait on the writeback
    page in the sense of "don't crash".

    > Also writeback seems to be only used by nfs/afs/nilfs2, not in
    > the normal case, unless I'm misreading the code.
    >
    > The nilfs2 case seems weird, I haven't completely read that.

    I'll take a look at that :)

    > > Then the writeback pages simply won't reach here. And it won't
    > > magically go into writeback state, since the page has been locked.
    >
    > But since we take the page lock they should not be in writeback anyways,
    > no?

    No, writeback pages are normally not locked. But the dirty => writeback
    transition is locked.

    Thanks,
    Fengguang


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