On Tue Sep 22 2009 at 20:06:40 +0200, Manuel Bouyer wrote: > On Sun, Sep 20, 2009 at 08:23:38PM +0300, Antti Kantee wrote: > > > In ufs_ihashget(), vget() can return a vnode that has been vclean'ed > > > because > > > vget() can sleep. After vget returns, check that vp is still connected > > > with > > > ip, and that ip still points to the inode we want. This fix the NULL > > > pointer dereference in ufs_fhtovp() I've been seeing on a NFS server. > > > > Um, hold the phone. The whole point of vget() is to provide race-free > > access to the weak vnode reference held by the file system. Are you > > saying this does not hold anymore? > > It depends on what you mean with "race-free". If you mean that the > vnode returned by vget() can't be recygled, I think this is true. > If you mean that vget() can't return a clean vnode then this is false: > vget() can sleep in vn_lock(), and it releases the v_interlock mutex before > sleeping. While sleeping vclean() can VOP_RECLAIM() the vnode, even > if v_usecount is > 1.
What is the practical difference of "cleaned" and "recycled" for the file system driver? If there is a race in vfs and XLOCK is not used properly, I think that should be investigated and fixed instead of patching file systems here and there.
