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    SubjectRe: [PATCH v1 1/1] fs/splice: add missing callback for inaccessible pages
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    On 30.04.20 21:32, Dave Hansen wrote:
    > On 4/30/20 11:12 AM, Christian Borntraeger wrote:
    >> On 29.04.20 18:07, Dave Hansen wrote:
    >>> On 4/28/20 3:50 PM, Claudio Imbrenda wrote:
    >>>> If a page is inaccesible and it is used for things like sendfile, then
    >>>> the content of the page is not always touched, and can be passed
    >>>> directly to a driver, causing issues.
    >>>>
    >>>> This patch fixes the issue by adding a call to arch_make_page_accessible
    >>>> in page_cache_pipe_buf_confirm; this fixes the issue.
    >>> I spent about 5 minutes putting together a patch:
    >>>
    >>> https://sr71.net/~dave/intel/accessible.patch
    >> You only set the page flag for compound pages. that of course leaves a big pile
    >> of pages marked a not accessible, thus explaining the sendto trace and all kind
    >> of other random traces.
    >
    > Ahh, nice catch! That does explain an oddity or two that I saw.
    >
    >> What do you see when you also do the SetPageAccessible(page);
    >> in the else page of prep_new_page (order == 0).
    >> (I do get > 10000 of these non compound page allocs just during boot).
    >
    > Yes, I see the same thing.
    >
    > I updated the patch and double-checked that it triggers properly with a
    > socket-based sendfile().

    Do you have a calltrace?

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