[PATCH-v4 1/7] vfs: split update_time() into update_time() and write_time()

[Christoph Hellwig]

On Thu, Nov 27, 2014 at 01:34:29PM +0100, Jan Kara wrote:
>   But Ted changed XFS to copy timestamps to on-disk structure from the
> in-memory inode fields after VFS updated the timestamps. So the stamps
> should be coherent AFAICT, shouldn't they?

Not coherent enough.  We need the XFS ilock to synchronize reading from
and writing to the time stamps.  update_time() only has i_mutex, which
we can't take for the transaction commit path.