Hi,
Quite often I see "panic: unmount: dangling vnode". My test
regress/sys/kern/mount triggers it, but it also happens when rebooting
virtual machines.
The problem is, when dirty buffers are flushed to disk, the unmount
process sleeps. If the file system is busy, other processes can
create new dirty buffers by writing files.
First I tired to block these writes. But this is very complex. A
much simpler solution is to flush a few times. With this diff I
could not trigger the problem anymore.
Is that fix good enough?
bluhm
Index: kern/vfs_subr.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/vfs_subr.c,v
retrieving revision 1.293
diff -u -p -r1.293 vfs_subr.c
--- kern/vfs_subr.c 26 Aug 2019 18:56:29 -0000 1.293
+++ kern/vfs_subr.c 20 Nov 2019 20:50:31 -0000
@@ -962,14 +962,20 @@ int
vflush(struct mount *mp, struct vnode *skipvp, int flags)
{
struct vflush_args va;
+ int loopcnt;
va.skipvp = skipvp;
va.busy = 0;
va.flags = flags;
- vfs_mount_foreach_vnode(mp, vflush_vnode, &va);
-
- if (va.busy)
- return (EBUSY);
+ for (loopcnt = 10; loopcnt > 0; loopcnt--) {
+ vfs_mount_foreach_vnode(mp, vflush_vnode, &va);
+ if (va.busy)
+ return (EBUSY);
+ if ((flags & FORCECLOSE) == 0)
+ break;
+ if (LIST_EMPTY(&mp->mnt_vnodelist))
+ break;
+ }
return (0);
}
