Bug 48755

Got a panic right now on 5.0-p2/i386, probably related to filesystem
stuff:

# gdb -k /boot/kernel/kernel ./vmcore.0 
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This GDB was configured as "i386-undermydesk-freebsd"...(no debugging symbols found)...
panic: bwrite: buffer is not busy???
panic messages:
---
panic: pmap_enter: attempted pmap_enter on 4MB page

syncing disks, buffers remaining... panic: bwrite: buffer is not busy???
Uptime: 17h3m21s
Dumping 511 MB
ata0: resetting devices ..
done
 16 32[CTRL-C to abort]  48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288 304 320 336 352 368 384 400 416 432 448[CTRL-C to abort]  464 480 496
---
#0  0xc01de84b in doadump ()
(kgdb) bt
#0  0xc01de84b in doadump ()
#1  0xc01decd6 in boot ()
#2  0xc01def23 in panic ()
#3  0xc021d692 in bwrite ()
#4  0xc021ec4e in vfs_bio_awrite ()
#5  0xc02ca63a in ffs_fsync ()
#6  0xc02c987e in ffs_sync ()
#7  0xc023070b in sync ()
#8  0xc01de94c in boot ()
#9  0xc01def23 in panic ()
#10 0xc031afed in pmap_enter ()
#11 0xc02dc8d4 in vm_fault ()
#12 0xc031e45f in trap_pfault ()
#13 0xc031df52 in trap ()
#14 0xc030f048 in calltrap ()
---Can't read userspace from dump, or kernel process---

I'll keep the crashdump for a while, in case someone wants
to extract some more info.