Re: pbulk hang in 5.99.21

[enami tsugutomo <tsugutomo.enami%jp.sony.com@localhost>]

> On Sun, Nov 08, 2009 at 11:38:15AM +0100, Thomas Klausner wrote:
> > I've just upgraded my 5.99.21 from Oct 22 to Nov 8 (kernel and
> > userland, packages not rebuilt), and now a pbulk (set up in a tmpfs)
> > hangs during the scan phase. Output including some ctrl-t:
> 
> Still happens with today's 5.99.22.

Here is a workaround I'm trying now.

enami.

Index: sys/kern/vfs_subr.c
===================================================================
RCS file: /cvsroot/src/sys/kern/vfs_subr.c,v
retrieving revision 1.386
diff -u -r1.386 vfs_subr.c
--- sys/kern/vfs_subr.c 5 Nov 2009 08:18:02 -0000       1.386
+++ sys/kern/vfs_subr.c 11 Nov 2009 06:02:33 -0000
@@ -1386,7 +1386,7 @@
 vrelel(vnode_t *vp, int flags)
 {
        bool recycle, defer;
-       int error;
+       int error, islayer_vnode;
 
        KASSERT(mutex_owned(&vp->v_interlock));
        KASSERT((vp->v_iflag & VI_MARKER) == 0);
@@ -1425,6 +1425,7 @@
                 * XXX This ugly block can be largely eliminated if
                 * locking is pushed down into the file systems.
                 */
+               islayer_vnode = (vp->v_iflag & VI_LAYER) != 0;
                if (curlwp == uvm.pagedaemon_lwp) {
                        /* The pagedaemon can't wait around; defer. */
                        defer = true;
@@ -1432,13 +1433,18 @@
                        /* We have to try harder. */
                        vp->v_iflag &= ~VI_INACTREDO;
                        error = vn_lock(vp, LK_EXCLUSIVE | LK_INTERLOCK |
-                           LK_RETRY);
+                           (islayer_vnode ? LK_NOWAIT : LK_RETRY));
                        if (error != 0) {
-                               /* XXX */
-                               vpanic(vp, "vrele: unable to lock %p");
-                       }
-                       defer = false;
-               } else if ((vp->v_iflag & VI_LAYER) != 0) {
+                               if (islayer_vnode) {
+                                       defer = true;
+                                       mutex_enter(&vp->v_interlock);
+                               } else {
+                                       /* XXX */
+                                       vpanic(vp, "vrele: unable to lock %p");
+                               }
+                       } else
+                               defer = false;
+               } else if (islayer_vnode) {
                        /* 
                         * Acquiring the stack's lock in vclean() even
                         * for an honest vput/vrele is dangerous because