lkml.org 
[lkml]   [2011]   [Jan]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [announce] vfs-scale git tree update
On Tue, Jan 11, 2011 at 7:59 PM, Ian Kent <raven@themaw.net> wrote:
>
> Isn't the parent i_mutex held during mkdir()?

Yes, but a lookup that hits in the dentry cache won't actually take
the parent mutex.

So as far as I can tell, doing the "d_add()" before setting d_op can
result in another CPU coming in and seeing the newly added dentry
before d_op has actually been initialized. Exactly because it will do
the dentry lookup without holding any mutex.

Of course, it's a very small window, so it probably doesn't matter in practice.

>> 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.

Alex, care to test just removing the d_set_d_op() call from autofs4_lookup()?

(That code is a bit scary, though - it explicitly makes it a negative
dentry with a d_instantiate(dentry, NULL), and then hides the inode
information away separately. Scary scary)

Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2011-01-12 05:09    [from the cache]
©2003-2011 Jasper Spaans