Merge branch 'master' into upstream-fixes

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 460f1c43238e..1ad674fd348c 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2844,7 +2844,6 @@ int try_to_free_buffers(struct page *page)
 
         spin_lock(&mapping->private_lock);
         ret = drop_buffers(page, &buffers_to_free);
-        spin_unlock(&mapping->private_lock);
 
         /*
          * If the filesystem writes its buffers by hand (eg ext3)
@@ -2855,9 +2854,14 @@ int try_to_free_buffers(struct page *page)
          * Also, during truncate, discard_buffer will have marked all
          * the page's buffers clean.  We discover that here and clean
          * the page also.
+         *
+         * private_lock must be held over this entire operation in order
+         * to synchronise against __set_page_dirty_buffers and prevent the
+         * dirty bit from being lost.
          */
         if (ret)
                 cancel_dirty_page(page, PAGE_CACHE_SIZE);
+        spin_unlock(&mapping->private_lock);
 out:
         if (buffers_to_free) {
                 struct buffer_head *bh = buffers_to_free;