[src/ad-namecache]: src/sys/kern - rb_tree_insert_node() refuses to insert du...

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

details:   https://anonhg.NetBSD.org/src/rev/617b9b8e199b
branches:  ad-namecache
changeset: 983030:617b9b8e199b
user:      ad <ad%NetBSD.org@localhost>
date:      Sun Mar 22 01:58:22 2020 +0000

description:
- rb_tree_insert_node() refuses to insert duplicate nodes.  It always
  returns a pointer to the current node in the tree for the given key.
  Therefore the call to rb_tree_lookup_node() in cache_enter() is not
  needed.

- Adjust a comment and move some code for clarity.

diffstat:

 sys/kern/vfs_cache.c |  22 +++++++++++-----------
 1 files changed, 11 insertions(+), 11 deletions(-)

diffs (72 lines):

diff -r 65e30fda0641 -r 617b9b8e199b sys/kern/vfs_cache.c
--- a/sys/kern/vfs_cache.c      Sun Mar 22 00:34:31 2020 +0000
+++ b/sys/kern/vfs_cache.c      Sun Mar 22 01:58:22 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_cache.c,v 1.126.2.15 2020/03/22 00:34:31 ad Exp $  */
+/*     $NetBSD: vfs_cache.c,v 1.126.2.16 2020/03/22 01:58:22 ad Exp $  */
 
 /*-
  * Copyright (c) 2008, 2019, 2020 The NetBSD Foundation, Inc.
@@ -171,7 +171,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.126.2.15 2020/03/22 00:34:31 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.126.2.16 2020/03/22 01:58:22 ad Exp $");
 
 #define __NAMECACHE_PRIVATE
 #ifdef _KERNEL_OPT
@@ -416,8 +416,6 @@
         * Search the RB tree for the key.  This is an inlined lookup
         * tailored for exactly what's needed here (64-bit key and so on)
         * that is quite a bit faster than using rb_tree_find_node(). 
-        * Elsewhere during entry/removal the usual functions are used as it
-        * doesn't matter there.
         */
        for (;;) {
                if (__predict_false(RB_SENTINEL_P(node))) {
@@ -525,6 +523,9 @@
                return false;
        }
 
+       /* Compute the key up front - don't need the lock. */
+       key = cache_key(name, namelen);
+
        /* Could the entry be purged below? */
        if ((cnflags & ISLASTCN) != 0 &&
            ((cnflags & MAKEENTRY) == 0 || nameiop == CREATE)) {
@@ -533,9 +534,6 @@
                op = RW_READER;
        }
 
-       /* Compute the key up front - don't need the lock. */
-       key = cache_key(name, namelen);
-
        /* Now look for the name. */
        rw_enter(&dvi->vi_nc_lock, op);
        ncp = cache_lookup_entry(dvp, name, namelen, key);
@@ -890,18 +888,20 @@
        /*
         * Insert to the directory.  Concurrent lookups in the same
         * directory may race for a cache entry.  There can also be hash
-        * value collisions.  If there's a entry there already, free it.
+        * value collisions.  If there's a entry there already, purge it.
         */
        rw_enter(&dvi->vi_nc_lock, RW_WRITER);
-       oncp = rb_tree_find_node(&dvi->vi_nc_tree, &ncp->nc_key);
-       if (oncp) {
+       oncp = rb_tree_insert_node(&dvi->vi_nc_tree, ncp);
+       if (oncp != ncp) {
+               KASSERT(oncp->nc_key == ncp->nc_key);
                KASSERT(oncp->nc_nlen == ncp->nc_nlen);
                if (cache_namecmp(oncp, name, namelen)) {
                        COUNT(ncs_collisions);
                }
                cache_remove(oncp, true);
+               oncp = rb_tree_insert_node(&dvi->vi_nc_tree, ncp);
+               KASSERT(oncp == ncp);
        }
-       rb_tree_insert_node(&dvi->vi_nc_tree, ncp);
 
        /* Then insert to the vnode. */
        if (vp == NULL) {