On Wed, 16 Feb 2005, Jeff Moyer wrote:
> ==> Regarding Re: [PATCH] dcache d_drop() bug fix / __d_drop() use fix;
> [EMAIL PROTECTED] adds:
>
> raven> On Wed, 16 Feb 2005, Jan Blunck wrote:
> >> This is a re-submission of the patch I sent about a month ago.
> >>
> >> While working on my code I realized that d_drop() might race against
> >> __d_lookup(). __d_drop() (which is called by d_drop() after acquiring the
> >> dcache_lock) is accessing dentry->d_flags to set the DCACHE_UNHASHED flag.
> >> This shouldn't be done without holding dentry->d_lock, like stated in
> >> dcache.h:
> >>
> >> struct dentry {
> >> ...
> >> unsigned int d_flags; /* protected by d_lock */
> >> ...
> >> };
> >>
> >> Therefore d_drop() must acquire the dentry->d_lock. Likewise every use of
> >> __d_drop() must acquire that lock.
> >>
> >> This patch fixes d_drop() and every grep'able __d_drop() use. This patch
> >> is
> >> against today's http://linux.bkbits.net/linux-2.5.
> >>
>
> raven> For my part, in autofs4, I would prefer:
>
> > --- linux-2.6.9/fs/autofs4/root.c.d_lock 2005-02-16 23:15:18.000000000
> > +0800
> > +++ linux-2.6.9/fs/autofs4/root.c 2005-02-16 23:15:35.000000000 +0800
> > @@ -621,7 +621,7 @@
> > spin_unlock(&dcache_lock);
> > return -ENOTEMPTY;
> > }
> > - __d_drop(dentry);
> > + d_drop(dentry);
> > spin_unlock(&dcache_lock);
>
> > dput(ino->dentry);
>
> Ian, this would deadlock. You already hold the dcache lock here, and
> d_drop takes it:
Ha!
Yes. There is a difference between d_lock and dcache_lock.
I need glasses!
Please ignore what I said.
Ian
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