Date: Tue, 23 Sep 2008 15:09:40 -0400 From: John Baldwin <jhb@freebsd.org> To: arch@freebsd.org Cc: pjd@freebsd.org Subject: Using a file-backed swap via md0 results in panic on reboot.. Message-ID: <200809231509.40279.jhb@freebsd.org>
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So if you attach an md device to a file and then use that md0 device for swap,
you will get a panic on shutdown if the swap file was in use. The reason is
that we remove swap devices _after_ unmounting the filesystems in boot():
if (nbusy) {
/*
* Failed to sync all blocks. Indicate this and don't
* unmount filesystems (thus forcing an fsck on reboot).
*/
printf("Giving up on %d buffers\n", nbusy);
DELAY(5000000); /* 5 seconds */
} else {
if (!first_buf_printf)
printf("Final sync complete\n");
/*
* Unmount filesystems
*/
if (panicstr == 0)
vfs_unmountall();
}
swapoff_all();
DELAY(100000); /* wait for console output to finish */
Is there any reason we can't move the swapoff_all()? Should we perhaps only
do it in "clean" case? Alternatively, should the swapoff_all() during
shutdown have a special flag so that it doesn't actually read in any data
from disk and just throws away the data instead? Sample panic:
Waiting (max 60 seconds) for system process `vnlru' to stop...done
Waiting (max 60 seconds) for system process `syncer' to stop...
Syncing disks, vnodes remaining...2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0
0 0 done
Waiting (max 60 seconds) for system process `bufdaemon' to stop...done
All buffers synced.
Swap device ad0s1b removed.
swap_pager: I/O error - pagein failed; blkno 2097177,size 4096, error 5
panic: swap_pager_force_pagein: read from swap failed
cpuid = 0
KDB: stack backtrace:
panic() at panic+0x2c5
swapoff_one() at swapoff_one+0x5bb
swapoff_all() at swapoff_all+0xe4
boot() at boot+0x871
reboot() at reboot+0x45
syscall() at syscall+0x642
Xfast_syscall() at Xfast_syscall+0xa8
--
John Baldwin
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