[PATCH -next] mm/hmm/test: fix missing unlock on error in dmirror_migrate_finalize_and_map()

[Wei Yongjun]

Add the missing unlock before return from function
dmirror_migrate_finalize_and_map() in the error
handling case.

Fixes: 5d5e54be8a1e ("mm/hmm/test: add selftest driver for HMM")
Reported-by: Hulk Robot <hul...@huawei.com>
Signed-off-by: Wei Yongjun <weiyongj...@huawei.com>
---
 lib/test_hmm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 00bca6116f93..30462193c4ff 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -647,8 +647,10 @@ static int dmirror_migrate_finalize_and_map(struct 
migrate_vma *args,
                if (*dst & MIGRATE_PFN_WRITE)
                        entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
                entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);
-               if (xa_is_err(entry))
+               if (xa_is_err(entry)) {
+                       mutex_unlock(&dmirror->mutex);
                        return xa_err(entry);
+               }
        }
 
        mutex_unlock(&dmirror->mutex);