mm: soft offline: split thp at the beginning of soft_offline_page()

Naoya Horiguchi · torvalds · commit 783657a7dc20 · 2012-11-30T08:51:18.000-08:00
When we try to soft-offline a thp tail page, put_page() is called on the
tail page unthinkingly and VM_BUG_ON is triggered in put_compound_page().

This patch splits thp before going into the main body of soft-offlining.

Signed-off-by: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Cc: Andi Kleen &lt;andi@firstfloor.org&gt;
Cc: Tony Luck &lt;tony.luck@intel.com&gt;
Cc: Andi Kleen &lt;andi.kleen@intel.com&gt;
Cc: Wu Fengguang &lt;fengguang.wu@intel.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
@@ -1476,9 +1476,17 @@ int soft_offline_page(struct page *page, int flags)
 {
 	int ret;
 	unsigned long pfn = page_to_pfn(page);
+	struct page *hpage = compound_trans_head(page);
 
 	if (PageHuge(page))
 		return soft_offline_huge_page(page, flags);
+	if (PageTransHuge(hpage)) {
+		if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
+			pr_info("soft offline: %#lx: failed to split THP\n",
+				pfn);
+			return -EBUSY;
+		}
+	}
 
 	ret = get_any_page(page, pfn, flags);
 	if (ret < 0)
