Panic using networked swap with 6.0-BETA1

[Greg Lewis]

Hi,

No response on freebsd-sparc, plus I think this may be MI, so I'm sending
it to freebsd-current too.

I have a Ultra 10 which I network boot in a diskless configuration to run
FreeBSD.  This weekend I downloaded 6.0-BETA1 and got that set up.  I've
gotten the following panic reproduceably while trying to compile the
lang/perl5.8 port when the machine starts to swap.

Note that this is typed in from looking at the console (I'd need to set
up a serial console) so apologies for any typos.

panic: bstrategy: no bufobj bp=0xc3dee258
cpuid = 0
KDB: enter: panic
[thread pid 7 tid 100027 ]
Stopped at      kdb_enter+0x3c: ta           %xcc, 1
db> trace
Tracing pid 7 tid 100027 td 0xfffff80017df84c0
panic() at panic+0x16c
swapdev_strategy() at swapdev_strategy+0x70
swp_pager_strategy() at swp_page_strategy+0x8c
swap_pager_putpages() at swap_pager_putpages+0x3e8
default_pager_putpages() at default_pager_putpages+0x1c
vm_pageout_flush() at vm_pageout_flush+0x14c
vm_pageout_clean() at vm_pageout_clean+0x334
vm_pageout_scan() at vm_pageout_scan+0x738
vm_pageout() at vm_pageout+0x3e8
fork_exit() at fork_exit+0x94
fork_trampoline() at fork_trampoline+0x8
db>

Please let me know if you want anything else examined from the debugger.

The server is an x86 box running FreeBSD 4.11-STABLE:

FreeBSD misty.eyesbeyond.com 4.11-STABLE FreeBSD 4.11-STABLE #0: Thu Apr  7 10:51:05 MDT 2005     glewis at misty.eyesbeyond.com:/usr/src/sys/compile/MISTY  i386

I created the swap file on the server as follows:

dd if=/dev/zero of=swap bs=4k count=128k

The fstab entry looks like:

/swap                                   none    swap    sw      0       0

I downloaded 5.4 and tried it tonight and network swap works without any
problems, so the behaviour in 6.0-BETA1 appears to definitely be a
regression.

In addition, I tried a similar trick on my Alpha with 6.0-BETA1 tonight and
received a similar panic:

panic: bstrategy: no bufobj bp=0xfffffe0003358010                               
cpuid = 0                                                                       
KDB: enter: panic                                                               
[thread pid 8 tid 100025 ]                                                      
Stopped at      kdb_enter+0x48: or      zero,zero,zero  <zero=0x0>              
db> trace                                                                       
Tracing pid 8 tid 100025 td 0xfffffc0007bbed20                                  
kdb_enter() at kdb_enter+0x48                                                   
panic() at panic+0x210                                                          
swapdev_strategy() at swapdev_strategy+0xb8                                     
swp_pager_strategy() at swp_pager_strategy+0xac                                 
swap_pager_putpages() at swap_pager_putpages+0x4c4                              
default_pager_putpages() at default_pager_putpages+0x1c                         
vm_pageout_flush() at vm_pageout_flush+0x1d8                                    
db>

I haven't tried it under 5.4 on the Alpha yet, but networked swap
definitely worked under 5.2 on the Alpha.

-- 
Greg Lewis                          Email   : glewis at eyesbeyond.com
Eyes Beyond                         Web     : http://www.eyesbeyond.com
Information Technology              FreeBSD : glewis at FreeBSD.org