dax: Remove optimisation from dax_lock_mapping_entry

Skipping some of the revalidation after we sleep can lead to returning
a mapping which has already been freed.  Just drop this optimisation.

Reported-by: Dan Williams <dan.j.williams@intel.com>
Fixes: 9f32d221301c ("dax: Convert dax_lock_mapping_entry to XArray")
Signed-off-by: Matthew Wilcox <willy@infradead.org>

1 files changed, 2 insertions, 5 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 616e36ea6aaa..529ac9d7c10a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -383,11 +383,8 @@ bool dax_lock_mapping_entry(struct page *page)
                 entry = xas_load(&xas);
                 if (dax_is_locked(entry)) {
                         entry = get_unlocked_entry(&xas);
-                        /* Did the page move while we slept? */
-                        if (dax_to_pfn(entry) != page_to_pfn(page)) {
-                                xas_unlock_irq(&xas);
-                                continue;
-                        }
+                        xas_unlock_irq(&xas);
+                        continue;
                 }
                 dax_lock_entry(&xas, entry);
                 xas_unlock_irq(&xas);