mm/memory-failure.c: move set_migratetype_isolate() outside get_any_page()

Chen Gong pointed out that set/unset_migratetype_isolate() was done in
different functions in mm/memory-failure.c, which makes the code less
readable/maintainable.  So this patch does it in soft_offline_page().

With this patch, we get to hold lock_memory_hotplug() longer but it's
not a problem because races between memory hotplug and soft offline are
very rare.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Chen, Gong <gong.chen@linux.intel.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -1422,19 +1422,6 @@ static int __get_any_page(struct page *p, unsigned long pfn, int flags)
 	if (flags & MF_COUNT_INCREASED)
 		return 1;
 
-	/*
-	 * The lock_memory_hotplug prevents a race with memory hotplug.
-	 * This is a big hammer, a better would be nicer.
-	 */
-	lock_memory_hotplug();
-
-	/*
-	 * Isolate the page, so that it doesn't get reallocated if it
-	 * was free. This flag should be kept set until the source page
-	 * is freed and PG_hwpoison on it is set.
-	 */
-	if (get_pageblock_migratetype(p) != MIGRATE_ISOLATE)
-		set_migratetype_isolate(p, true);
 	/*
 	 * When the target page is a free hugepage, just remove it
 	 * from free hugepage list.
@@ -1455,7 +1442,6 @@ static int __get_any_page(struct page *p, unsigned long pfn, int flags)
 		/* Not a free page */
 		ret = 1;
 	}
-	unlock_memory_hotplug();
 	return ret;
 }
 
@@ -1654,15 +1640,28 @@ int soft_offline_page(struct page *page, int flags)
 		}
 	}
 
+	/*
+	 * The lock_memory_hotplug prevents a race with memory hotplug.
+	 * This is a big hammer, a better would be nicer.
+	 */
+	lock_memory_hotplug();
+
+	/*
+	 * Isolate the page, so that it doesn't get reallocated if it
+	 * was free. This flag should be kept set until the source page
+	 * is freed and PG_hwpoison on it is set.
+	 */
+	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
+		set_migratetype_isolate(page, true);
+
 	ret = get_any_page(page, pfn, flags);
-	if (ret < 0)
-		goto unset;
-	if (ret) { /* for in-use pages */
+	unlock_memory_hotplug();
+	if (ret > 0) { /* for in-use pages */
 		if (PageHuge(page))
 			ret = soft_offline_huge_page(page, flags);
 		else
 			ret = __soft_offline_page(page, flags);
-	} else { /* for free pages */
+	} else if (ret == 0) { /* for free pages */
 		if (PageHuge(page)) {
 			set_page_hwpoison_huge_page(hpage);
 			dequeue_hwpoisoned_huge_page(hpage);
@@ -1673,7 +1672,6 @@ int soft_offline_page(struct page *page, int flags)
 			atomic_long_inc(&num_poisoned_pages);
 		}
 	}
-unset:
 	unset_migratetype_isolate(page, MIGRATE_MOVABLE);
 	return ret;
 }