Yeah, this particular one really should only bite you with
DEBUG_PAGEALLOC.
The SG code potentially _derefences_ a field past the end of the SG array,
but it should be a read, and the result should never be used (it's used to
calculate the pointer to past the end of the queue, so if it's used,
there's another bug lurking).
Please do. I wouldn't be surprised if it's also related to the SG changes,
but I don't think it's the exact particular bug that Ingo saw.
Linus
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