mm/madvise: fix madvise_[un]lock() issue

We are asymmetric in our locking/unlocking in the case of memory failure
madvise() behaviour options, correct this and abstract the memory failure
check.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Lorenzo Stoakes <[email protected]>
Reported-by: "Lai, Yi" <[email protected]>
Closes: https://lore.kernel.org/Z6rgiVp7221r4JZ5@ly-workstation
Reviewed-by: SeongJae Park <[email protected]>
Tested-by: SeongJae Park <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Naresh Kamboju <[email protected]>
Cc: Shakeel Butt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: lorenzo-stoakes

mm/madvise.c

@@ -1575,26 +1575,43 @@ int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
 }
 #endif /* CONFIG_ANON_VMA_NAME */
 
-static int madvise_lock(struct mm_struct *mm, int behavior)
-{
-
 #ifdef CONFIG_MEMORY_FAILURE
-	if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
-		return 0;
+static bool is_memory_failure(int behavior)
+{
+	switch (behavior) {
+	case MADV_HWPOISON:
+	case MADV_SOFT_OFFLINE:
+		return true;
+	default:
+		return false;
+	}
+}
+#else
+static bool is_memory_failure(int behavior)
+{
+	return false;
+}
 #endif
 
+static int madvise_lock(struct mm_struct *mm, int behavior)
+{
+	if (is_memory_failure(behavior))
+	    return 0;
+
 	if (madvise_need_mmap_write(behavior)) {
 		if (mmap_write_lock_killable(mm))
 			return -EINTR;
 	} else {
 		mmap_read_lock(mm);
 	}
 	return 0;
-
 }
 
 static void madvise_unlock(struct mm_struct *mm, int behavior)
 {
+	if (is_memory_failure(behavior))
+	    return;
+
 	if (madvise_need_mmap_write(behavior))
 		mmap_write_unlock(mm);
 	else