On 20.11.19 01:46, Wei Yang wrote:
On Tue, Nov 19, 2019 at 01:23:54PM +0100, David Hildenbrand wrote:
On 18.11.19 09:20, Wei Yang wrote:
PageHuge is handled by memory_failure_hugetlb(), so this case could be
removed.
Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 3151c87dff73..392ac277b17d 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1359,10 +1359,7 @@ int memory_failure(unsigned long pfn, int flags)
* page_remove_rmap() in try_to_unmap_one(). So to determine page status
* correctly, we save a copy of the page flags at this time.
*/
- if (PageHuge(p))
- page_flags = hpage->flags;
- else
- page_flags = p->flags;
+ page_flags = p->flags;
/*
* unpoison always clear PG_hwpoison inside page lock
I somewhat miss a proper explanation why this is safe to do. We access page
flags here, so why is it safe to refer to the ones of the sub-page?
Hi, David
I think your comment is on this line:
page_flags = p->flags;
Maybe we need to use this:
page_flags = hpage->flags;
And use hpage in the following or even the whole function?
While one thing interesting is not all "compound page" is PageCompound. For
some sub-page, we can't get the correct head. This means we may just check on
the sub-page.
Oh wait, I think I missed the check right at the beginning of this
function, sorry :/
Sooo, memory_failure_hugetlb() was introduced by
commit 761ad8d7c7b5485bb66fd5bccb58a891fe784544
Author: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Date: Mon Jul 10 15:47:47 2017 -0700
mm: hwpoison: introduce memory_failure_hugetlb()
and essentially ripped out all PageHuge() checks *except* this check.
This check was introduced in
commit 7258ae5c5a2ce2f5969e8b18b881be40ab55433d
Author: James Morse <james.morse@xxxxxxx>
Date: Fri Jun 16 14:02:29 2017 -0700
mm/memory-failure.c: use compound_head() flags for huge pages
Maybe that was just a merge oddity as both commits are only ~1month
apart. IOW, I think Naoya's patch forgot to rip it out.
Can we make this clear in the patch description like "This is dead code
that cannot be reached after commit 761ad8d7c7b5 ("mm: hwpoison:
introduce memory_failure_hugetlb()")"
I assume Andrew can fix up when applying
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
