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

[Lorenzo Stoakes]

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

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
 mm/madvise.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index b5ef8e03d8b0..1a7af59c3aa9 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1575,14 +1575,29 @@ 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;
@@ -1590,11 +1605,13 @@ static int madvise_lock(struct mm_struct *mm, int behavior)
 		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
--
2.48.1