On Wed, 12 Jan 2011 11:59:36 +0800, Ian Kent <raven@xxxxxxxxxx> wrote: > On Tue, 2011-01-11 at 11:57 -0600, Alex Elder wrote: > > On Tue, 2011-01-11 at 08:51 -0800, Linus Torvalds wrote: > > > On Tue, Jan 11, 2011 at 8:34 AM, Alex Elder <aelder@xxxxxxx> wrote: > > > > > > > > FYI, when using this code, as merged by Linus, I hit the > > > > BUG_ON() at the beginning of d_set_d_op() when it's called > > > > by autofs4_dir_mkdir(). I managed to work around it by > > > > just commenting out those BUG_ON() calls but it's something > > > > that ought to get addressed properly. > > > > > > Yeah, removing the BUG_ON() isn't the right thing to do - it means > > > that autofs4 is obviously setting the dentry ops twice for the same > > > dentry. > > > > > > Possibly the thing could be relaxed to allow setting the _same_ d_op > > > pointer, ie do something like > > > > > > if (dentry->d_op == op) > > > return; > > > > > > at the top of that function. But looking at it, I don't think that > > > fixes the autofs4 issue. > > > > That's easy enough, but it seems everybody else ensures > > this gets done just once per dentry, and it would be nice > > to preserve that "tightness" if possible. > > > > > The fact that autofs4 does "d_add()" before it sets the d_ops (or > > > other dentry state, for that matter) looks a bit scary. To me that > > > smells like it might get a dentry lookup hit before it's actually > > > fully done. > > > > Agreed. > > Isn't the parent i_mutex held during mkdir()? > Still the order can be changed, of course. > > > > > > Does it make any difference if you move the various d_add() calls down > > > to the end of the functions to when the "dentry" has really been > > > instantiated? > > > > Looking at it quickly, I don't think that would matter for > > the case at hand. I.e., that might be safer but it doesn't > > address the fact that these fields are getting initialized > > multiple times. > > Yeah, a hangover from changes done over time. > Not setting the dentry op in ->lookup() should fix this. > for 9p I did the other way round. lookup now set the dentry op for both negative and positive dentries and rest of the place we dropped d_set_d_op (b8b80cf37c7f0e32729262f805bc0fa81c3e9d12 have the details) -aneesh -- 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
