1 files changed, 17 insertions, 3 deletions

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index dd7f852746cb..8e67abf05985 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -404,12 +404,26 @@ static int cachefiles_attr_changed(struct fscache_object *_object)
         if (oi_size == ni_size)
                 return 0;
 
-        newattrs.ia_size = ni_size;
-        newattrs.ia_valid = ATTR_SIZE;
-
         cachefiles_begin_secure(cache, &saved_cred);
         mutex_lock(&object->backer->d_inode->i_mutex);
+
+        /* if there's an extension to a partial page at the end of the backing
+         * file, we need to discard the partial page so that we pick up new
+         * data after it */
+        if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
+                _debug("discard tail %llx", oi_size);
+                newattrs.ia_valid = ATTR_SIZE;
+                newattrs.ia_size = oi_size & PAGE_MASK;
+                ret = notify_change(object->backer, &newattrs);
+                if (ret < 0)
+                        goto truncate_failed;
+        }
+
+        newattrs.ia_valid = ATTR_SIZE;
+        newattrs.ia_size = ni_size;
         ret = notify_change(object->backer, &newattrs);
+
+truncate_failed:
         mutex_unlock(&object->backer->d_inode->i_mutex);
         cachefiles_end_secure(cache, saved_cred);