[User-mode-linux-devel] Swapspace - kernel BUG in swapspace.c

[William S. <wst...@po...>]

Good day, Jeff and all,
	In shutting down redhat 6.9.5 (and stock redhat 6.2, incase you
were wondering), I got a few segfaults and a kernel bug.  This is the
first time I've used a swapfile in a while.

Saving random seed [  OK  ]
Stopping portmap services: [  OK  ]
Shutting down interface eth0 [  OK  ]
Shutting down kernel logger: [  OK  ]
Shutting down system logger: [  OK  ]
Starting killall [  OK  ]
Sending all processes the TERM signal...
Sending all processes the KILL signal..
Turning off swap kernel BUG at swapfile.c:300!

	(system fails to shutdown.)  The only command line parameters used
were: ./linux-2.4.0-test8 mem=32M ubd1=swap , where swap is a 126M
mkswap'ed swap file on the host.
	linux/mm/swapfile.c has:

static void unuse_vma(struct vm_area_struct * vma, pgd_t *pgdir,
                        swp_entry_t entry, struct page* page)
{
        unsigned long start = vma->vm_start, end = vma->vm_end;

        if (start >= end)
                BUG();
        do {
                unuse_pgd(vma, pgdir, start, end - start, entry, page);
                start = (start + PGDIR_SIZE) & PGDIR_MASK;
                pgdir++;
        } while (start && (start < end));
}

	, with the sole BUG line being line 300.
	I don't get it at every shutdown, but have gotten it a few
times.  While I do use a sparse root filesystem, this bug shows up whether
the swapfile on the host is sparse or not.
	UML kernel is the Jeff's stock 2.4.0-test8, host kernel is
2.4.0-test9-pre4 with Mingo's VM fix and the ptrace EIP lines removed -
essentially 2.4.0-test9-pre5.
	Cheers,
	- Bill

---------------------------------------------------------------------------
	"When in danger or in doubt, run in circles, scream and shout."
	-- Troubleshooters creed.
--------------------------------------------------------------------------
William Stearns (wst...@po...).  Mason, Buildkernel, named2hosts, 
and ipfwadm2ipchains are at:                http://www.pobox.com/~wstearns
LinuxMonth; articles for Linux Enthusiasts! http://www.linuxmonth.com
--------------------------------------------------------------------------