hwpoison: call action_result() in failure path of hwpoison_user_mappings()

hwpoison_user_mappings() could fail for various reasons, so printk()s to
print out the reasons should be done in each failure check inside
hwpoison_user_mappings().

And currently we don't call action_result() when hwpoison_user_mappings()
fails, which is not consistent with other exit points of memory error
handler.  So this patch fixes these messaging problems.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Chen Yucong <slaoub@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -911,8 +911,10 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	if (!page_mapped(hpage))
 		return SWAP_SUCCESS;
 
-	if (PageKsm(p))
+	if (PageKsm(p)) {
+		pr_err("MCE %#lx: can't handle KSM pages.\n", pfn);
 		return SWAP_FAIL;
+	}
 
 	if (PageSwapCache(p)) {
 		printk(KERN_ERR
@@ -1235,7 +1237,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 */
 	if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
 	    != SWAP_SUCCESS) {
-		printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
+		action_result(pfn, "unmapping failed", IGNORED);
 		res = -EBUSY;
 		goto out;
 	}