panic: softdep_deallocate_dependencies: unrecovered I/O error

Hi there,

Just now my pretty fresh 11-CURRENT rebooted unexpectedly in the middle of
'svn up'.  Some information from core.txt.0 (full version available upon
request) given in the end of this email.  (Machine: 11.0-CURRENT/i386 built
on Oct 18, GENERIC kernel, default install, single / partition with J+SU.)

This particular crash is worrisome for me for the following reasons:

- I had lost some data; /usr/ports (checked out copy) become corrupted:
  some files have zero size; also svn(1) now reports that repo version is
  12(!); I never had experienced such a fuckup with FreeBSD in years; it
  makes 10.0 look particularly bad: I can even cope with FreeBSD becoming
  bloated and slow, but I definitely cannot tolerate data loss -- we are
  not Linux after all;

- I've already seen these 'error=11' messaged on -CURRENT before, again,
  while doing 'svn up'; I've followed up [1] about it on -hackers_at_ on Oct
  1st; avg_at_ game me some advice [2], but I did not have a chance to see if
  it helps yet (I've never seen those errors again on my laptop, until it
  happened today on another box also running -CURRENT); perhaps this panic
  can somehow expedite investigation.

./danfe

[1] http://docs.freebsd.org/cgi/mid.cgi?20131001192955.GA27965
[2] http://docs.freebsd.org/cgi/mid.cgi?524B2555.7030408

Unread portion of the kernel message buffer:
g_vfs_done():ada0s3a[WRITE(offset=11688411136, length=32768)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11688476672, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11688607744, length=32768)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11689328640, length=32768)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11689394176, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11689525248, length=65536)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11689820160, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11690704896, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11691196416, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11691327488, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11691458560, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11691589632, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11691720704, length=131072)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=11692081152, length=98304)]error = 11
g_vfs_done():ada0s3a[WRITE(offset=10815619072, length=4096)]error = 11
/: got error 11 while accessing filesystem
panic: softdep_deallocate_dependencies: unrecovered I/O error
cpuid = 0
KDB: stack backtrace:
#0 0xc0aed942 at kdb_backtrace+0x52
#1 0xc0ab37e1 at panic+0x121
#2 0xc0d044b1 at softdep_deallocate_dependencies+0x71
#3 0xc0b39ce6 at brelse+0x86
#4 0xc0b3d470 at bufdone+0x60
#5 0xc0a1967a at g_vfs_done+0x27a
#6 0xc0b3cf24 at biodone+0x54
#7 0xc0a15f04 at g_io_schedule_up+0x1d4
#8 0xc0a1649d at g_up_procbody+0x6d
#9 0xc0a82ab3 at fork_exit+0xa3
#10 0xc0f77794 at fork_trampoline+0x8
<...>
(kgdb) #0  doadump (textdump=-961984384) at pcpu.h:233
#1  0xc0ab3459 in kern_reboot (howto=260)
    at /usr/src/sys/kern/kern_shutdown.c:447
#2  0xc0ab381f in panic (fmt=<value optimized out>)
    at /usr/src/sys/kern/kern_shutdown.c:754
#3  0xc0d044b1 in softdep_deallocate_dependencies (bp=<value optimized out>)
    at /usr/src/sys/ufs/ffs/ffs_softdep.c:13595
#4  0xc0b39ce6 in brelse (bp=0xe1a8b850) at buf.h:427
#5  0xc0b3d470 in bufdone (bp=<value optimized out>)
    at /usr/src/sys/kern/vfs_bio.c:3759
#6  0xc0a1967a in g_vfs_done (bip=<value optimized out>)
    at /usr/src/sys/geom/geom_vfs.c:161
#7  0xc0b3cf24 in biodone (bp=0xce43fe40) at /usr/src/sys/kern/vfs_bio.c:3579
#8  0xc0a15f04 in g_io_schedule_up (tp=0xc6a91930)
    at /usr/src/sys/geom/geom_io.c:799
#9  0xc0a1649d in g_up_procbody (arg=0x0) at /usr/src/sys/geom/geom_kern.c:98
#10 0xc0a82ab3 in fork_exit (callout=0xc0a16430 <g_up_procbody>)
    at /usr/src/sys/kern/kern_fork.c:995
#11 0xc0f77794 in fork_trampoline () at /usr/src/sys/i386/i386/exception.s:279