Re: CVS commit: src

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

On Feb 27, 2014, at 7:01 PM, Mindaugas Rasiukevicius 
<rmind%netbsd.org@localhost> wrote:

> "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost> wrote:
>>> I have not had time to follow your VFS changes, but can you explain why
>>> did you remove VOP_LOCK/VOP_UNLOCK in tmpfs_reclaim()?  It was added to
>>> prevent from the racy access of tn_links.
>> 
>> Hopefully a vnode lock is needed to access tn_links -- otherwise the
>> VOP_LOCK/UNLOCK in tmpfs_reclaim() didn't protect it ...
> 
> Yes, tn_links is modified with the vnode lock held.  Unlocked access in
> VOP_RECLAIM() racing with the release of the last last reference, used to
> cause crashes due to premature reclamation attempts.  Given that VOP_LOCK()
> acquires the vnode node, can you explain why this "didn't protect it"?

As stated above I hoped tn_links is modified only with the lock held.

>> As this commit prevents other threads from obtaining a lock while
>> VOP_RECLAIM() is running the protection should be the same as before.
> 
> You mean VOP_RECLAIM() is now called with the vnode lock held?  Can you
> please add an assert in tmpfs_reclaim() which demonstrates that?

No -- while VOP_RECLAIM() is called no thread may get the lock which is
the same as if it were held here.

--
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig 
(Germany)