[PATCH] mm: mincore: add hwpoison page handle

[PATCH] mm: mincore: add hwpoison page handle

[Weijie Yang]

When encounter pte is a swap entry, the current code handles two cases:
migration and normal swapentry, but we have a third case: hwpoison page.

This patch adds hwpoison page handle, consider hwpoison page incore as
same as migration.

Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
---
 mm/mincore.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/mincore.c b/mm/mincore.c
index 725c809..3545f13 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -137,8 +137,8 @@ static void mincore_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 		} else { /* pte is a swap entry */
 			swp_entry_t entry = pte_to_swp_entry(pte);
 
-			if (is_migration_entry(entry)) {
-				/* migration entries are always uptodate */
+			if (non_swap_entry(entry)) {
+			/* migration or hwpoison entries are always uptodate */
 				*vec = 1;
 			} else {
 #ifdef CONFIG_SWAP
-- 
1.7.0.4


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Re: [PATCH] mm: mincore: add hwpoison page handle

[Johannes Weiner]

On Wed, Nov 12, 2014 at 11:39:29AM +0800, Weijie Yang wrote:
> When encounter pte is a swap entry, the current code handles two cases:
> migration and normal swapentry, but we have a third case: hwpoison page.
> 
> This patch adds hwpoison page handle, consider hwpoison page incore as
> same as migration.
> 
> Signed-off-by: Weijie Yang <weijie.yang@samsung.com>

The change makes sense:

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

But please add a description of what happens when a poison entry is
encountered with the current code.  I'm guessing swap_address_space()
will return garbage and this might crash the kernel?

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Re: [PATCH] mm: mincore: add hwpoison page handle

[Naoya Horiguchi]

On Wed, Nov 12, 2014 at 09:20:22AM -0500, Johannes Weiner wrote:
> On Wed, Nov 12, 2014 at 11:39:29AM +0800, Weijie Yang wrote:
> > When encounter pte is a swap entry, the current code handles two cases:
> > migration and normal swapentry, but we have a third case: hwpoison page.
> > 
> > This patch adds hwpoison page handle, consider hwpoison page incore as
> > same as migration.
> > 
> > Signed-off-by: Weijie Yang <weijie.yang@samsung.com>

Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

> 
> The change makes sense:
> 
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> 
> But please add a description of what happens when a poison entry is
> encountered with the current code.  I'm guessing swap_address_space()
> will return garbage and this might crash the kernel?

Yes, I think that's correct.

Thanks,
Naoya Horiguchi
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