ocfs2: _really_ sync the right range

commit 64b4e2526d1cf6e6a4db6213d6e2b6e6ab59479a upstream.

"ocfs2 syncs the wrong range" had been broken; prior to it the
code was doing the wrong thing in case of O_APPEND, all right,
but _after_ it we were syncing the wrong range in 100% cases.
*ppos, aka iocb->ki_pos is incremented prior to that point,
so we are always doing sync on the area _after_ the one we'd
written to.

Spotted by Joseph Qi <joseph.qi@huawei.com> back in January;
unfortunately, I'd missed his mail back then ;-/

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 0de24a2..6a7a3d9 100644 (file)
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2387,10 +2387,14 @@ out_dio:
        /* buffered aio wouldn't have proper lock coverage today */
        BUG_ON(ret == -EIOCBQUEUED && !(file->f_flags & O_DIRECT));
 
+       if (unlikely(written <= 0))
+               goto no_sync;
+
        if (((file->f_flags & O_DSYNC) && !direct_io) || IS_SYNC(inode) ||
            ((file->f_flags & O_DIRECT) && !direct_io)) {
-               ret = filemap_fdatawrite_range(file->f_mapping, *ppos,
-                                              *ppos + count - 1);
+               ret = filemap_fdatawrite_range(file->f_mapping,
+                                              iocb->ki_pos - written,
+                                              iocb->ki_pos - 1);
                if (ret < 0)
                        written = ret;
 
@@ -2403,10 +2407,12 @@ out_dio:
                }
 
                if (!ret)
-                       ret = filemap_fdatawait_range(file->f_mapping, *ppos,
-                                                     *ppos + count - 1);
+                       ret = filemap_fdatawait_range(file->f_mapping,
+                                                     iocb->ki_pos - written,
+                                                     iocb->ki_pos - 1);
        }
 
+no_sync:
        /*
         * deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a ocfs2_dio_end_io
         * function pointer which is called when o_direct io completes so that