Messages in this thread | | | From | David Howells <> | Subject | Re: [RFC PATCH v2 1/3] mm: Don't pin ZERO_PAGE in pin_user_pages() | Date | Fri, 26 May 2023 10:15:26 +0100 |
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Lorenzo Stoakes <lstoakes@gmail.com> wrote:
> > iov_iter_extract_pages(), on the other hand, is only used in two places > > with these patches and the pins are always released with > > unpin_user_page*() so it's a lot easier to audit. > > Thanks for the clarification. I guess these are the cases where you're > likely to see zero page usage, but since this is changing all PUP*() callers > don't you need to audit all of those too?
I don't think it should be necessary. This only affects pages obtained from gup with FOLL_PIN - and, so far as I know, those always have to be released with unpin_user_page*() which is part of the gup API and thus it should be transparent to the users.
Pages obtained FOLL_GET, on the other hand, aren't freed through the gup API - and there are a bunch of ways of releasing them - and getting additional refs too.
David
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