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    SubjectRe: [RFC Patch 0/2] mm: Add parameters to make kernel behavior at memory error on dirty cache selectable
    On Thu, Apr 11, 2013 at 03:49:16PM +0200, Andi Kleen wrote:
    > > As a result, if the dirty cache includes user data, the data is lost,
    > > and data corruption occurs if an application uses old data.
    >
    > The application cannot use old data, the kernel code kills it if it
    > would do that. And if it's IO data there is an EIO triggered.
    >
    > iirc the only concern in the past was that the application may miss
    > the asynchronous EIO because it's cleared on any fd access.
    >
    > This is a general problem not specific to memory error handling,
    > as these asynchronous IO errors can happen due to other reason
    > (bad disk etc.)
    >
    > If you're really concerned about this case I think the solution
    > is to make the EIO more sticky so that there is a higher chance
    > than it gets returned. This will make your data much more safe,
    > as it will cover all kinds of IO errors, not just the obscure memory
    > errors.

    I'm interested in this topic, and in previous discussion, what I was said
    is that we can't expect user applications to change their behaviors when
    they get EIO, so globally changing EIO's stickiness is not a great approach.
    I'm working on a new pagecache tag based mechanism to solve this.
    But it needs time and more discussions.
    So I guess Tanino-san suggests giving up on dirty pagecache errors
    as a quick solution.

    Thanks,
    Naoya


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