dax: Avoid losing wakeup in dax_lock_mapping_entry

commit 25bbe21bf427a81b8e3ccd480ea0e1d940256156 upstream.

After calling get_unlocked_entry(), you have to call
put_unlocked_entry() to avoid subsequent waiters losing wakeups.

Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()")
Cc: stable@vger.kernel.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/dax.c b/fs/dax.c
index 0fb270f..b0cd136 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -217,6 +217,9 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot)
        return (void *)entry;
 }
 
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+                                      pgoff_t index, void *entry);
+
 /*
  * Lookup entry in radix tree, wait for it to become unlocked if it is
  * exceptional entry and return it. The caller must call
@@ -256,8 +259,10 @@ static void *__get_unlocked_mapping_entry(struct address_space *mapping,
                revalidate = wait_fn();
                finish_wait(wq, &ewait.wait);
                xa_lock_irq(&mapping->i_pages);
-               if (revalidate)
+               if (revalidate) {
+                       put_unlocked_mapping_entry(mapping, index, entry);
                        return ERR_PTR(-EAGAIN);
+               }
        }
 }