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    SubjectRe: [net PATCH] skb: Do mix page pool and page referenced frags in GRO


    On 27/01/2023 00.13, Jakub Kicinski wrote:
    > On Thu, 26 Jan 2023 11:06:59 -0800 Alexander Duyck wrote:
    >> From: Alexander Duyck<alexanderduyck@fb.com>
    >>
    >> GSO should not merge page pool recycled frames with standard reference
    >> counted frames. Traditionally this didn't occur, at least not often.
    >> However as we start looking at adding support for wireless adapters there
    >> becomes the potential to mix the two due to A-MSDU repartitioning frames in
    >> the receive path. There are possibly other places where this may have
    >> occurred however I suspect they must be few and far between as we have not
    >> seen this issue until now.
    >>
    >> Fixes: 53e0961da1c7 ("page_pool: add frag page recycling support in page pool")
    >> Reported-by: Felix Fietkau<nbd@nbd.name>
    >> Signed-off-by: Alexander Duyck<alexanderduyck@fb.com>
    > Exciting investigation!
    > Felix, out of curiosity - the impact of loosing GRO on performance is
    > not significant enough to care? We could possibly try to switch to
    > using the frag list if we can't merge into frags safely.

    Using the frag list sounds scary, because we recently learned that
    kfree_skb_list requires all SKBs on the list to have same refcnt (else
    the walking of the list can lead to other bugs).

    --Jesper

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