[src/ad-namecache]: src/sys/kern - Get shared locks on the directories, excep...

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

details:   https://anonhg.NetBSD.org/src/rev/3886bbf8042e
branches:  ad-namecache
changeset: 982986:3886bbf8042e
user:      ad <ad%NetBSD.org@localhost>
date:      Fri Jan 17 21:54:27 2020 +0000

description:
- Get shared locks on the directories, except for VOP_GETATTR() which
  unfortunately still needs LK_EXCLUSIVE due to itimes handling in UFS.

- vnode locks are not needed to traverse the namecache.

diffstat:

 sys/kern/vfs_getcwd.c |  21 ++++++++++-----------
 1 files changed, 10 insertions(+), 11 deletions(-)

diffs (85 lines):

diff -r 00642ee1f2ae -r 3886bbf8042e sys/kern/vfs_getcwd.c
--- a/sys/kern/vfs_getcwd.c     Fri Jan 17 21:53:01 2020 +0000
+++ b/sys/kern/vfs_getcwd.c     Fri Jan 17 21:54:27 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_getcwd.c,v 1.53.2.1 2020/01/17 21:47:35 ad Exp $ */
+/* $NetBSD: vfs_getcwd.c,v 1.53.2.2 2020/01/17 21:54:27 ad Exp $ */
 
 /*-
  * Copyright (c) 1999 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_getcwd.c,v 1.53.2.1 2020/01/17 21:47:35 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_getcwd.c,v 1.53.2.2 2020/01/17 21:54:27 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -107,6 +107,9 @@
        int len, reclen;
        tries = 0;
 
+       /* Upgrade to exclusive for UFS VOP_GETATTR (itimes) & VOP_LOOKUP. */
+       vn_lock(lvp, LK_UPGRADE | LK_RETRY);
+
        /*
         * If we want the filename, get some info we need while the
         * current directory is still locked.
@@ -142,7 +145,7 @@
        }
        uvp = *uvpp;
        /* Now lvp is unlocked, try to lock uvp */
-       error = vn_lock(uvp, LK_EXCLUSIVE);
+       error = vn_lock(uvp, LK_SHARED);
        if (error) {
                *lvpp = NULL;
                *uvpp = NULL;
@@ -254,7 +257,7 @@
                vput(tvp);
                vref(uvp);
                *uvpp = uvp;
-               vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY);
+               vn_lock(uvp, LK_SHARED | LK_RETRY);
                goto unionread;
        }
 #endif
@@ -310,7 +313,7 @@
         */
 
        VOP_UNLOCK(lvp);
-       vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY);
+       vn_lock(uvp, LK_SHARED | LK_RETRY);
        vrele(lvp);
        *lvpp = NULL;
 
@@ -349,7 +352,7 @@
         *      uvp is either NULL, or locked and held.
         */
 
-       vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
+       vn_lock(lvp, LK_SHARED | LK_RETRY);
        if (bufp)
                bp = *bpp;
 
@@ -396,7 +399,7 @@
                                goto out;
                        }
                        vref(lvp);
-                       error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
+                       error = vn_lock(lvp, LK_SHARED | LK_RETRY);
                        if (error != 0) {
                                vrele(lvp);
                                lvp = NULL;
@@ -557,11 +560,7 @@
        bp = bend = &path[len];
        *(--bp) = '\0';
 
-       error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
-       if (error != 0)
-               return error;
        error = cache_revlookup(vp, &dvp, &bp, path);
-       VOP_UNLOCK(vp);
        if (error != 0)
                return (error == -1 ? ENOENT : error);