Messages in this thread Patch in this message |  | | From | Oscar Salvador <> | Subject | [PATCH 3/7] mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED | Date | Thu, 19 Nov 2020 11:57:12 +0100 |
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From: Naoya Horiguchi <naoya.horiguchi@nec.com>
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.
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com> Signed-off-by: Oscar Salvador <osalvador@suse.de> --- mm/madvise.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c index c6b5524add58..7a0f64b93635 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -900,20 +900,23 @@ static int madvise_inject_error(int behavior, */ size = page_size(compound_head(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 (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); } else { 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); } -- 2.26.2
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