The patch titled
Subject: mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED
has been added to the -mm tree. Its filename is
mmmadvise-call-soft_offline_page-without-mf_count_increased.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mmmadvise-call-soft_offline_page-without-mf_count_increased.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mmmadvise-call-soft_offline_page-without-mf_count_increased.patch
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------------------------------------------------------
From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Subject: mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED
The call to get_user_pages_fast is only to get the pointer to a struct
page of a given address, pinning it is memory-poisoning handler's job, so
drop the refcount grabbed by get_user_pages_fast().
Note that the target page is still pinned after this put_page() because
the current process should have refcount from mapping.
Link: http://lkml.kernel.org/r/20200731122112.11263-4-nao.horiguchi@xxxxxxxxx
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Dmitry Yakunin <zeil@xxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/madvise.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
--- a/mm/madvise.c~mmmadvise-call-soft_offline_page-without-mf_count_increased
+++ a/mm/madvise.c
@@ -893,16 +893,24 @@ static int madvise_inject_error(int beha
*/
size = page_size(compound_head(page));
- if (PageHWPoison(page)) {
- put_page(page);
+ /*
+ * The get_user_pages_fast() is just to get the pfn of the
+ * given address, and the refcount has nothing to do with
+ * what we try to test, so it should be released immediately.
+ * This is racy but it's intended because the real hardware
+ * errors could happen at any moment and memory error handlers
+ * must properly handle the race.
+ */
+ put_page(page);
+
+ if (PageHWPoison(page))
continue;
- }
if (behavior == MADV_SOFT_OFFLINE) {
pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
pfn, start);
- ret = soft_offline_page(pfn, MF_COUNT_INCREASED);
+ ret = soft_offline_page(pfn, 0);
if (ret)
return ret;
continue;
@@ -910,14 +918,6 @@ static int madvise_inject_error(int beha
pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
pfn, start);
-
- /*
- * Drop the page reference taken by get_user_pages_fast(). In
- * the absence of MF_COUNT_INCREASED the memory_failure()
- * routine is responsible for pinning the page to prevent it
- * from being released back to the page allocator.
- */
- put_page(page);
ret = memory_failure(pfn, 0);
if (ret)
return ret;
_
Patches currently in -mm which might be from naoya.horiguchi@xxxxxxx are
mmhwpoison-cleanup-unused-pagehuge-check.patch
mm-hwpoison-remove-recalculating-hpage.patch
mmmadvise-call-soft_offline_page-without-mf_count_increased.patch
mmhwpoison-inject-dont-pin-for-hwpoison_filter.patch
mmhwpoison-remove-mf_count_increased.patch
mmhwpoison-remove-flag-argument-from-soft-offline-functions.patch
mmhwpoison-introduce-mf_msg_unsplit_thp.patch
mmhwpoison-double-check-page-count-in-__get_any_page.patch
