Re: [V9fs-developer] [GIT PULL] 9p file system bug fixes for 2.6.35-rc2

[Aneesh Kumar K. V]

On Wed, 30 Jun 2010 09:48:15 -0700, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Jun 30, 2010 at 4:52 AM, Aneesh Kumar K. V
> <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > You are correct. we cannot drop the rename lock in between. I also found
> > another issue in that we are using dentry->d_name.name directly. That
> > would imply we need to hold the rename_lock even during the
> > client_walk.
> 
> Yes.
> 
> >ÂHow about the patch below ?. I updated the patch to hold
> > rename_lock during multiple path walk. Also the rename path is updated
> > to hold the lock during p9_client_rename operations.
> 
> I'm not finding any obvious problems with this, and you're right that
> you also need to hold the rename write-lock even for regular renames
> (not just cross-directory ones) in order to protect the name itself.
> So those two patches together seem to be ok at a quick glance.
> 
> That said, I do wonder if you wouldn't be better off copying the name
> components in order to then drop the lock earlier. That way you'd only
> need to hold the lock while walking the dentries, and could possibly
> release it during the actual walk (unless you need the names to be
> stable, but I don't think you can rely on that anyway, since other
> clients might be doing renames concurrently.. I don't know)
> 
>                        Linus


Updated patch