Re: [patch] futex-2.5.40-B5

[Oleg Nesterov <oleg@tv-sign.ru>]

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.