Re: Some questions about memory allocation and BKL

[Jan Hudec <bulb@ucw.cz>]

On Sun, Oct 26, 2003 at 21:21:31 +0800, Ian Kent wrote:
> On Sun, 26 Oct 2003, Jan Hudec wrote:
> > No. It is forbiden to turn dentry to negative one unless you are the
> > only holder (it has refcount 1). See d_delete().
> 
> Sorry, my bad description. I was thinking about if (...) to check 
> fields which I think, acording to the discussion, is OK but ...

inode and name are constant, so don't need lock. all the lists need
dcache_lock (subdirs, hash etc...). Parent should need dcache_lock too
(try to look it up in rename code). I don't know about mountpoint, but
obviously requires some locking.

> > You only need to hold the lock when you check whether the dentry is
> > hashed. And you need to use the atomic_* functions to access the
> > refcount.
> 
> Does that also include tests on a list in the dentry.
> I think that you said that this is what needs the lock, correct?
> 
> For example:
> 
> if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))
> 	...
> 
> needs the dcache_lock?

I assume yes. The tree lists should need dcache_lock.

-------------------------------------------------------------------------------
						 Jan 'Bulb' Hudec <bulb@ucw.cz>