Re: [patch] futex-2.5.40-B5

Oleg Nesterov (oleg@tv-sign.ru)
Sat, 05 Oct 2002 04:00:10 +0400


Hello.

Ingo Molnar wrote:
> the new lookup code first does a lightweight follow_page(), then if no
> page is present we do the get_user_pages() thing.

What if futex placed in VM_HUGETLB area?
Then follow_page() return garbage.

I beleive in i386 case it can be fixed something like this:

--- mm/memory.c.orig Sat Oct 5 01:08:54 2002
+++ mm/memory.c Sat Oct 5 03:31:28 2002
@@ -480,6 +480,17 @@ follow_page(struct mm_struct *mm, unsign
if (pmd_none(*pmd) || pmd_bad(*pmd))
goto out;

+#ifdef CONFIG_HUGETLB_PAGE
+ if (pmd_large(pmd)) {
+ ptep = (pte_t *) pmd;
+
+ if (write && !pte_write(*ptep))
+ return NULL;
+
+ return pte_page(*ptep) + ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
+ }
+#endif
+
ptep = pte_offset_map(pmd, address);
if (!ptep)
goto out;

Then follow_hugetlb_page() hook can be killed.

Oleg.
-
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