vn_lock & ffs_snapremove

[Alexander Kabaev]

On Fri, 28 Apr 2006 16:00:30 +0300
Kostik Belousov <kostikbel at gmail.com> wrote:

> Look at the two code fragments
> 
> 1. from vn_lock(9):
> 
> 		error = VOP_LOCK(vp, flags | LK_INTERLOCK, td);
> 		flags &= ~LK_INTERLOCK;
> 		KASSERT((flags & LK_RETRY) == 0 || error == 0,
> 		    ("LK_RETRY set with incompatible flags %d\n",
> flags)); /*
> 		 * Callers specify LK_RETRY if they wish to get dead
> vnodes.
> 		 * If RETRY is not set, we return ENOENT instead.
> 		 */
> 		if (error == 0 && vp->v_iflag & VI_DOOMED &&
> 		    (flags & LK_RETRY) == 0) {
> 			VOP_UNLOCK(vp, 0, td);
> 			error = ENOENT;
> 			break;
> 		}
> 
> 2. ffs_snapremove(9):
> 
> (vp->v_vnlock for snapshot vnode vp points to sn_snlock)
> 		lkp = vp->v_vnlock;
> 		vp->v_vnlock = &vp->v_lock;
> 
> Is there anything that would prevent these two fragments to
> intervene ? Esp. bad looks the situation where VOP_LOCK() from
> vn_lock executed and locked doomed snapshot vnode, after that
> ffs_snapremove replaces vnode lock and VOP_UNLOCK attempted on
> _another_ lock.
> 
> If this scenario can happen (as it seems), then, probably,
> some measures like transferlockers(9) are needed ?
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Привет,

тут возникло предложение наказать тебя commit bit-ом. Интересует мнение
самого наказуемого на это предложение :)

-- 
Alexander Kabaev
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