increasing the size of the namecache suddenly made the comment

"This makes the algorithm O(n^2), but do you think I care?"
a lot more meaningful, as discovered by krw.
fix the loop so it doesn't restart all the time, as it's not necessary.
(this was also tried years ago in rev 1.20 and reverted, but that change
also introduced pool_put before the namecache was ready to free things. we
have been freeing cache entries with pool_put for some time now, so that's
been made safe.)
ok deraadt krw

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index 160a6b3..7781cfb 100644 (file)
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: vfs_cache.c,v 1.43 2015/01/12 20:00:11 tedu Exp $     */
+/*     $OpenBSD: vfs_cache.c,v 1.44 2015/01/16 17:05:49 tedu Exp $     */
 /*     $NetBSD: vfs_cache.c,v 1.13 1996/02/04 02:18:09 christos Exp $  */
 
 /*
@@ -448,10 +448,6 @@ cache_purge(struct vnode *vp)
 /*
  * Cache flush, a whole filesystem; called when filesys is umounted to
  * remove entries that would now be invalid
- *
- * The line "nxtcp = nchhead" near the end is to avoid potential problems
- * if the cache lru chain is modified while we are dumping the
- * inode.  This makes the algorithm O(n^2), but do you think I care?
  */
 void
 cache_purgevfs(struct mount *mp)
@@ -460,24 +456,20 @@ cache_purgevfs(struct mount *mp)
 
        /* whack the regular entries */
        for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) {
+               nxtcp = TAILQ_NEXT(ncp, nc_lru);
                if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) {
-                       nxtcp = TAILQ_NEXT(ncp, nc_lru);
                        continue;
                }
                /* free the resources we had */
                cache_zap(ncp);
-               /* cause rescan of list, it may have altered */
-               nxtcp = TAILQ_FIRST(&nclruhead);
        }
        /* whack the negative entries */
        for (ncp = TAILQ_FIRST(&nclruneghead); ncp != NULL; ncp = nxtcp) {
+               nxtcp = TAILQ_NEXT(ncp, nc_neg);
                if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) {
-                       nxtcp = TAILQ_NEXT(ncp, nc_neg);
                        continue;
                }
                /* free the resources we had */
                cache_zap(ncp);
-               /* cause rescan of list, it may have altered */
-               nxtcp = TAILQ_FIRST(&nclruneghead);
        }
 }