Date: Fri, 23 Feb 2001 15:59:59 +0100 (CET) From: mitja.horvat@hermes.si To: FreeBSD-gnats-submit@freebsd.org Subject: kern/25309: kernel panic related to umount -f & kevents Message-ID: <200102231459.f1NExwD15609@lamu.hermes.si>
next in thread | raw e-mail | index | archive | help
>Number: 25309
>Category: kern
>Synopsis: Bug with kevent & umount -f
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Feb 23 07:00:02 PST 2001
>Closed-Date:
>Last-Modified:
>Originator: Mitja Horvat
>Release: FreeBSD 4.2-STABLE i386
>Organization:
>Environment:
FreeBSD 4.2-STABLE i386, cvsupped on Feb 11th 2001.
PIII/800Mhz, 256MB of RAM, 15GB ATA/66 hard drive.
>Description:
Kernel panic occurs when waiting for a kevent on a UFS file and the
filesystem is forcibly unmounted.
>How-To-Repeat:
Since tail (in conjunction with -f) uses kevent to achieve it's job,
it can be used to reproduce the problem. Mount a filesystem, and
tail -f a file. Unmount the filesystem using the -f flag(force). Note,
that the bug may not manifestate immediately.
#!/bin/sh
while true
do
mount /dev/DEVICE /MOUNT_POINT
tail -f /MOUNT_POINT/RANDOM_FILE &
umount -f /MOUNT_POINT
kill %%
done
Replace /dev/DEVICE with a device(eg. CDROM), /MOUNT_POINT with the mount point
of the device, and RANDOM_FILE with a random file on the filesystem.
>Fix:
The following patch fixes the problem for me. Please note that I'm far away from being
a kernel hacker, so I'm not 100% sure if it breaks something else or not
(although it's a very simple fix).
--- vfs_vnops.c.orig Mon Feb 12 14:17:19 2001
+++ vfs_vnops.c Fri Feb 23 15:55:18 2001
@@ -722,6 +722,15 @@
struct vnode *vp = (struct vnode *)kn->kn_fp->f_data;
struct inode *ip = VTOI(vp);
+ /*
+ * If the underlying inode was freed(this can happen
+ * if the filesystem is forcibly unmounted with
+ * umount -f), return as there was activity on the file,
+ * so the process will be woken up and later it will
+ * receive an error during read XXX
+ */
+ if (ip == NULL) return 1;
+
kn->kn_data = ip->i_size - kn->kn_fp->f_offset;
return (kn->kn_data != 0);
}
>Release-Note:
>Audit-Trail:
>Unformatted:
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-bugs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200102231459.f1NExwD15609>