Subject: [merged] mm-hwpoison-fix-race-against-poison-thp.patch removed from -mm tree To: liwanp@xxxxxxxxxxxxxxxxxx,andi@xxxxxxxxxxxxxx,n-horiguchi@xxxxxxxxxxxxx,tony.luck@xxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Thu, 12 Sep 2013 12:45:25 -0700 The patch titled Subject: mm/hwpoison: fix race against poison thp has been removed from the -mm tree. Its filename was mm-hwpoison-fix-race-against-poison-thp.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx> Subject: mm/hwpoison: fix race against poison thp There is a race between hwpoison page and unpoison page, memory_failure set the page hwpoison and increase num_poisoned_pages without hold page lock, and one page count will be accounted against thp for num_poisoned_pages. However, unpoison can occur before memory_failure hold page lock and split transparent hugepage, unpoison will decrease num_poisoned_pages by 1 << compound_order since memory_failure has not yet split transparent hugepage with page lock held. That means we account one page for hwpoison and 1 << compound_order for unpoison. This patch fix it by inserting a PageTransHuge check before doing TestClearPageHWPoison, unpoison failed without clearing PageHWPoison and decreasing num_poisoned_pages. A B memory_failue TestSetPageHWPoison(p); if (PageHuge(p)) nr_pages = 1 << compound_order(hpage); else nr_pages = 1; atomic_long_add(nr_pages, &num_poisoned_pages); unpoison_memory nr_pages = 1<< compound_trans_order(page); if(TestClearPageHWPoison(p)) atomic_long_sub(nr_pages, &num_poisoned_pages); lock page if (!PageHWPoison(p)) unlock page and return hwpoison_user_mappings if (PageTransHuge(hpage)) split_huge_page(hpage); Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx> Suggested-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Cc: Andi Kleen <andi@xxxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory-failure.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff -puN mm/memory-failure.c~mm-hwpoison-fix-race-against-poison-thp mm/memory-failure.c --- a/mm/memory-failure.c~mm-hwpoison-fix-race-against-poison-thp +++ a/mm/memory-failure.c @@ -1342,6 +1342,16 @@ int unpoison_memory(unsigned long pfn) return 0; } + /* + * unpoison_memory() can encounter thp only when the thp is being + * worked by memory_failure() and the page lock is not held yet. + * In such case, we yield to memory_failure() and make unpoison fail. + */ + if (PageTransHuge(page)) { + pr_info("MCE: Memory failure is now running on %#lx\n", pfn); + return 0; + } + nr_pages = 1 << compound_order(page); if (!get_page_unless_zero(page)) { _ Patches currently in -mm which might be from liwanp@xxxxxxxxxxxxxxxxxx are origin.patch mm-drop-actor-argument-of-do_generic_file_read.patch mm-drop-actor-argument-of-do_generic_file_read-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html