On Wed, 2009-07-22 at 17:21 +0800, Amerigo Wang wrote: > Miklos Szeredi wrote: > > On Tue, 2009-07-21 at 18:07 +0800, Amerigo Wang wrote: > > > >> Andrew Morton wrote: > >> > >>> On Mon, 6 Jul 2009 01:35:30 -0400 > >>> Amerigo Wang <amwang@xxxxxxxxxx> wrote: > >>> > >>> > >>> > >>>> file_update_time() should be called with i_mutex held, > >>>> move it before mutex_unlock(). > >>>> > >>>> > >>>> > >>> Why do you believe that file_update_time() needs i_mutex? > >>> > >>> > >> file_update_time() modifies inode, no? :) > >> > > > > So does touch_atime(), yet neither needs i_mutex. > > > Yes? > > Then how the inode is protected when file_update_time() modifies > it? Protected against what? For example the inode isn't protected against concurrent access by stat(2), since that doesn't take i_mutex. And indeed it looks like there are races there, since set/get operations are not atomic on the timestamp, so stat could return a garbled value if it races with file_update_time() or touch_atime(). Possibly worth fixing, but I'm not sure how to do that without affecting the scalability of stat and friends and without adding too much complexity. Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
