Author: bz
Date: Wed Jun 20 08:34:29 2018
New Revision: 335437
URL: https://svnweb.freebsd.org/changeset/base/335437

Log:
  Sometimes it is helpful to get the path for a vnode.
  Implement a ddb function walking the namecache to do this.
  
  Reviewed by:          jhb, mjg
  Inspired by:          gdb macro from jhb (old version)
  Sponsored by:         iXsystems, Inc.
  Differential Revision:        https://reviews.freebsd.org/D14898

Modified:
  head/share/man/man4/ddb.4
  head/sys/kern/vfs_cache.c

Modified: head/share/man/man4/ddb.4
==============================================================================
--- head/share/man/man4/ddb.4   Wed Jun 20 07:02:19 2018        (r335436)
+++ head/share/man/man4/ddb.4   Wed Jun 20 08:34:29 2018        (r335437)
@@ -60,7 +60,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 24, 2017
+.Dd June 20, 2018
 .Dt DDB 4
 .Os
 .Sh NAME
@@ -1121,6 +1121,11 @@ header file.
 .Pp
 .It Ic show Cm vnodebufs Ar addr
 Shows clean/dirty buffer lists of the vnode located at
+.Ar addr .
+.\"
+.Pp
+.It Ic show Cm vpath Ar addr
+Walk the namecache to lookup the pathname of the vnode located at
 .Ar addr .
 .\"
 .Pp

Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c   Wed Jun 20 07:02:19 2018        (r335436)
+++ head/sys/kern/vfs_cache.c   Wed Jun 20 08:34:29 2018        (r335437)
@@ -37,6 +37,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_ddb.h"
 #include "opt_ktrace.h"
 
 #include <sys/param.h>
@@ -62,6 +63,10 @@ __FBSDID("$FreeBSD$");
 #include <sys/ktrace.h>
 #endif
 
+#ifdef DDB
+#include <ddb/ddb.h>
+#endif
+
 #include <vm/uma.h>
 
 SDT_PROVIDER_DECLARE(vfs);
@@ -2529,3 +2534,54 @@ out:
        free(fbuf, M_TEMP);
        return (error);
 }
+
+#ifdef DDB
+static void
+db_print_vpath(struct vnode *vp)
+{
+
+       while (vp != NULL) {
+               db_printf("%p: ", vp);
+               if (vp == rootvnode) {
+                       db_printf("/");
+                       vp = NULL;
+               } else {
+                       if (vp->v_vflag & VV_ROOT) {
+                               db_printf("<mount point>");
+                               vp = vp->v_mount->mnt_vnodecovered;
+                       } else {
+                               struct namecache *ncp;
+                               char *ncn;
+                               int i;
+
+                               ncp = TAILQ_FIRST(&vp->v_cache_dst);
+                               if (ncp != NULL) {
+                                       ncn = ncp->nc_name;
+                                       for (i = 0; i < ncp->nc_nlen; i++)
+                                               db_printf("%c", *ncn++);
+                                       vp = ncp->nc_dvp;
+                               } else {
+                                       vp = NULL;
+                               }
+                       }
+               }
+               db_printf("\n");
+       }
+
+       return;
+}
+
+DB_SHOW_COMMAND(vpath, db_show_vpath)
+{
+       struct vnode *vp;
+
+       if (!have_addr) {
+               db_printf("usage: show vpath <struct vnode *>\n");
+               return;
+       }
+
+       vp = (struct vnode *)addr;
+       db_print_vpath(vp);
+}
+
+#endif
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