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    SubjectRe: [PATCH v3 01/11] pagemap: Introduce ->memory_failure()
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    > On Mon, Feb 8, 2021 at 2:55 AM Shiyang Ruan <ruansy.fnst@cn.fujitsu.com> wrote:
    > >
    > > When memory-failure occurs, we call this function which is implemented
    > > by each kind of devices. For the fsdax case, pmem device driver
    > > implements it. Pmem device driver will find out the block device where
    > > the error page locates in, and try to get the filesystem on this block
    > > device. And finally call filesystem handler to deal with the error.
    > > The filesystem will try to recover the corrupted data if possiable.
    > >
    > > Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
    > > ---
    > > include/linux/memremap.h | 8 ++++++++
    > > 1 file changed, 8 insertions(+)
    > >
    > > diff --git a/include/linux/memremap.h b/include/linux/memremap.h
    > > index 79c49e7f5c30..0bcf2b1e20bd 100644
    > > --- a/include/linux/memremap.h
    > > +++ b/include/linux/memremap.h
    > > @@ -87,6 +87,14 @@ struct dev_pagemap_ops {
    > > * the page back to a CPU accessible page.
    > > */
    > > vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
    > > +
    > > + /*
    > > + * Handle the memory failure happens on one page. Notify the processes
    > > + * who are using this page, and try to recover the data on this page
    > > + * if necessary.
    > > + */
    > > + int (*memory_failure)(struct dev_pagemap *pgmap, unsigned long pfn,
    > > + int flags);
    > > };
    >
    > After the conversation with Dave I don't see the point of this. If
    > there is a memory_failure() on a page, why not just call
    > memory_failure()? That already knows how to find the inode and the
    > filesystem can be notified from there.

    We want memory_failure() supports reflinked files. In this case, we are not
    able to track multiple files from a page(this broken page) because
    page->mapping,page->index can only track one file. Thus, I introduce this
    ->memory_failure() implemented in pmem driver, to call ->corrupted_range()
    upper level to upper level, and finally find out files who are
    using(mmapping) this page.

    >
    > Although memory_failure() is inefficient for large range failures, I'm
    > not seeing a better option, so I'm going to test calling
    > memory_failure() over a large range whenever an in-use dax-device is
    > hot-removed.
    >

    I did not test this for large range failure yet... I am not sure if it works
    fine. But because of the complex tracking method, I think it would be more
    inefficient in this case than before.


    --
    Thanks,
    Ruan Shiyang.
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