Messages in this thread | | | Date | Thu, 15 Apr 2004 21:49:09 -0700 | From | Andrew Morton <> | Subject | Re: Fix bogus get_page() calls in hugepage code |
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David Gibson <david@gibson.dropbear.id.au> wrote: > > On Thu, Apr 15, 2004 at 09:30:11PM -0700, Andrew Morton wrote: > > David Gibson <david@gibson.dropbear.id.au> wrote: > > > > > > On some archs the functions used to implement follow_page() for > > > hugepages do a get_page(). This is unlike the normal-page path for > > > follow_page(), so presumably a bug. This patch fixes it. > > > > get_user_pages() is supposed to pin the pages which it placed into the > > callers pages[] array. > > > > And the caller of get_user_pages() is supposed to unpin those pages when > > they are finished with. > > > > So follow_hugetlb_page() is currently doing the right thing. The asymmetry > > with follow_page() is awkward, but the overall intent was to minimise the > > amount of impact which the hugepage code has on core MM. > > Yes, but I'm not talking about follow_hugetlb_page() (my patch doesn't > touch it). I'm talking about follow_huge_addr() and > follow_huge_pmd(). These are called to implement follow_page(). In > get_user_pages(), follow_pages() is bypassed bu the call to > follow_hugetlb_page(), but these extra get_pages() are presumably a > bug if follow_page() is called on a hugepage from somewhere other than > get_user_pages().
Oh, OK. IIRC that stuff was added to support futexes-in-large-pages. The caller holds ->page_table_lock, as does zap_hugepage_range(), so that seems fine.
> So I think my patch is correct.
yup, thanks. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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