On 06/01/2010 11:16 PM, Andrew Morton wrote:
On Thu, 27 May 2010 13:43:00 -0700 Doug Doan<dougd@xxxxxxxx> wrote:
When a copy-on-write occurs, we take one of two paths in handle_mm_fault:
through handle_pte_fault for normal pages, or through hugetlb_fault for huge pages.
In the normal page case, we eventually get to do_wp_page and call mmu notifiers
via ptep_clear_flush_notify. There is no callout to the mmmu notifiers in the
huge page case. This patch fixes that.
Signed-off-by: Doug Doan<dougd@xxxxxxxx>
---
[patch text/plain (802B)]
--- mm/hugetlb.c.orig 2010-05-27 13:07:58.569546314 -0700
+++ mm/hugetlb.c 2010-05-26 14:41:06.449296524 -0700
(In patch -p1 form, please. So a/mm/hugetlb.c)
@@ -2345,11 +2345,17 @@ retry_avoidcopy:
ptep = huge_pte_offset(mm, address& huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte))) {
/* Break COW */
+ mmu_notifier_invalidate_range_start(mm,
+ address& huge_page_mask(h),
+ (address& huge_page_mask(h)) + huge_page_size(h));
huge_ptep_clear_flush(vma, address, ptep);
set_huge_pte_at(mm, address, ptep,
make_huge_pte(vma, new_page, 1));
/* Make the old page be freed below */
new_page = old_page;
+ mmu_notifier_invalidate_range_end(mm,
+ address& huge_page_mask(h),
+ (address& huge_page_mask(h)) + huge_page_size(h));
}
page_cache_release(new_page);
page_cache_release(old_page);
This causes mmu_notifier_invalidate_range_start() to be called under
page_table_lock. The immediately preceding code seems to take some
care to avoid doing that. I took a quick look at other callsites and
cannot immediately see other cases where
mmu_notifier_invalidate_range_start/end() are called under that lock.
This may not introduce bugs with current notifier implementations (I
didn't check), but it does lessen flexibility?
In the normal page case, handle_pte_fault calls do_wp_page inside a spinlock on
ptl = pte_lockptr(mm, pmd), which uses mm->page_table_lock if USE_SPLIT_PTLOCKS
is not defined.
I don't understand what you mean by lessen flexibilty.
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