[src/trunk]: src/sys/kern - expose the now hidden namecache

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/536192528ad0
branches:  trunk
changeset: 459494:536192528ad0
user:      christos <christos%NetBSD.org@localhost>
date:      Fri Sep 13 14:01:33 2019 +0000

description:
- expose the now hidden namecache
- compare with USHRT_MAX since the max length grew (we could make it NAME_MAX)
- use kmem_alloc for entries > NCHNAMLEN so the namecache contains all
  possible entries.

diffstat:

 sys/kern/vfs_cache.c |  27 ++++++++++++++++-----------
 1 files changed, 16 insertions(+), 11 deletions(-)

diffs (98 lines):

diff -r fa436ef38c01 -r 536192528ad0 sys/kern/vfs_cache.c
--- a/sys/kern/vfs_cache.c      Fri Sep 13 13:59:31 2019 +0000
+++ b/sys/kern/vfs_cache.c      Fri Sep 13 14:01:33 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_cache.c,v 1.120 2017/03/18 22:36:56 riastradh Exp $        */
+/*     $NetBSD: vfs_cache.c,v 1.121 2019/09/13 14:01:33 christos Exp $ */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -58,8 +58,9 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.120 2017/03/18 22:36:56 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.121 2019/09/13 14:01:33 christos Exp $");
 
+#define __NAMECACHE_PRIVATE
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
 #include "opt_dtrace.h"
@@ -93,10 +94,6 @@
  * obtained from (dvp, name) where dvp refers to the directory
  * containing name.
  *
- * For simplicity (and economy of storage), names longer than
- * a maximum length of NCHNAMLEN are not cached; they occur
- * infrequently in any case, and are almost never of interest.
- *
  * Upon reaching the last segment of a path, if the reference
  * is for DELETE, or NOCACHE is set (rewrite), and the
  * name is located in the cache, it will be dropped.
@@ -589,7 +586,7 @@
 
        cpup = curcpu()->ci_data.cpu_nch;
        mutex_enter(&cpup->cpu_lock);
-       if (__predict_false(namelen > NCHNAMLEN)) {
+       if (__predict_false(namelen > USHRT_MAX)) {
                SDT_PROBE(vfs, namecache, lookup, toolong, dvp,
                    name, namelen, 0, 0);
                COUNT(cpup, ncs_long);
@@ -703,7 +700,7 @@
 
        cpup = curcpu()->ci_data.cpu_nch;
        mutex_enter(&cpup->cpu_lock);
-       if (__predict_false(namelen > NCHNAMLEN)) {
+       if (__predict_false(namelen > USHRT_MAX)) {
                COUNT(cpup, ncs_long);
                mutex_exit(&cpup->cpu_lock);
                /* found nothing */
@@ -868,7 +865,7 @@
 
        /* First, check whether we can/should add a cache entry. */
        if ((cnflags & MAKEENTRY) == 0 ||
-           __predict_false(namelen > NCHNAMLEN || !doingcache)) {
+           __predict_false(namelen > USHRT_MAX || !doingcache)) {
                SDT_PROBE(vfs, namecache, enter, toolong, vp, name, namelen,
                    0, 0);
                return;
@@ -882,6 +879,10 @@
                mutex_exit(namecache_lock);
        }
 
+       if (namelen > NCHNAMLEN) {
+               ncp = kmem_alloc(sizeof(*ncp) + namelen, KM_SLEEP);
+               cache_ctor(NULL, ncp, 0);
+       } else
        ncp = pool_cache_get(namecache_cache, PR_WAITOK);
        mutex_enter(namecache_lock);
        numcache++;
@@ -919,7 +920,7 @@
                ncp->nc_vlist.le_prev = NULL;
                ncp->nc_vlist.le_next = NULL;
        }
-       KASSERT(namelen <= NCHNAMLEN);
+       KASSERT(namelen <= USHRT_MAX);
        ncp->nc_nlen = namelen;
        memcpy(ncp->nc_name, name, (unsigned)ncp->nc_nlen);
        TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
@@ -970,7 +971,7 @@
        int error;
 
        TAILQ_INIT(&nclruhead);
-       namecache_cache = pool_cache_init(sizeof(struct namecache),
+       namecache_cache = pool_cache_init(sizeof(struct namecache) + NCHNAMLEN,
            coherency_unit, 0, 0, "ncache", NULL, IPL_NONE, cache_ctor,
            cache_dtor, NULL);
        KASSERT(namecache_cache != NULL);
@@ -1248,6 +1249,10 @@
                        LIST_REMOVE(ncp, nc_hash);
                        ncp->nc_hash.le_prev = NULL;
                }
+               if (ncp->nc_nlen > NCHNAMLEN) {
+                       cache_dtor(NULL, ncp);
+                       kmem_free(ncp, sizeof(*ncp) + ncp->nc_nlen);
+               } else
                pool_cache_put(namecache_cache, ncp);
                ncp = next;
        }