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Fix a braino in the v_id wraparound code. Give more (current) details 

in comment.

PR:		11307
Spotted by:	Ville-Pertti Keinonen <will@iki.fi>
This commit is contained in:
Poul-Henning Kamp 1999-04-24 17:58:14 +00:00
parent cf69fad236
commit 22f054e258
1 changed files with 17 additions and 9 deletions
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26
sys/kern/vfs_cache.c
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@ -34,7 +34,7 @@
* SUCH DAMAGE.
*
* @(#)vfs_cache.c 8.5 (Berkeley) 3/22/95
* $Id: vfs_cache.c,v 1.37 1997/12/19 23:18:37 bde Exp $
* $Id: vfs_cache.c,v 1.38 1998/09/09 07:41:41 bde Exp $
*/
#include <sys/param.h>
@ -318,13 +318,21 @@ nchinit()
}
/*
* Invalidate all entries to particular vnode.
* Invalidate all entries to a particular vnode.
*
* We actually just increment the v_id, that will do it. The stale entries
* will be purged by lookup as they get found. If the v_id wraps around, we
* need to ditch the entire cache, to avoid confusion. No valid vnode will
* ever have (v_id == 0).
* Remove all entries in the namecache relating to this vnode and
* change the v_id. We take the v_id from a global counter, since
* it becomes a handy sequence number in crash-dumps that way.
* No valid vnode will ever have (v_id == 0).
*
* XXX: Only time and the size of v_id prevents this from failing:
* XXX: In theory we should hunt down all (struct vnode*, v_id)
* XXX: soft references and nuke them, at least on the global
* XXX: v_id wraparound. The period of resistance can be extended
* XXX: by incrementing each vnodes v_id individually instead of
* XXX: using the global v_id.
*/
void
cache_purge(vp)
struct vnode *vp;
@ -336,9 +344,9 @@ cache_purge(vp)
while (!TAILQ_EMPTY(&vp->v_cache_dst))
cache_zap(TAILQ_FIRST(&vp->v_cache_dst));
nextid++;
while (nextid == vp->v_id || !nextid)
continue;
do
nextid++;
while (nextid == vp->v_id || !nextid);
vp->v_id = nextid;
vp->v_dd = vp;
vp->v_ddid = 0;