CIFS access to my netgear has recently stopped working

Looks like I figured it out. My / partition was full. I was getting these errors in my /var/log/samba/smbd.conf:

[2016/07/17 13:49:52.588165,  2] auth/auth.c:309(check_ntlm_password)
  check_ntlm_password:  authentication for user [sonos] -> [sonos] -> [sonos] succeeded
[2016/07/17 13:49:52.610935,  0] ../lib/util/tdb_wrap.c:65(tdb_wrap_log)
  tdb(/var/run/samba/locking.tdb): expand_file write of 8192 bytes failed (No space left on device)
[2016/07/17 13:49:52.611155,  0] locking/locking.c:905(share_mode_lock_destructor)
  store returned NT_STATUS_UNSUCCESSFUL
[2016/07/17 13:49:52.611337,  0] lib/util.c:1117(smb_panic)
  PANIC (pid 3938): could not store share mode entry: NT_STATUS_UNSUCCESSFUL
[2016/07/17 13:49:52.621784,  0] lib/util.c:1221(log_stack_trace)
  BACKTRACE: 23 stack frames:
   #0 /usr/sbin/smbd(log_stack_trace+0x2d) [0x844aa6d]
   #1 /usr/sbin/smbd(smb_panic+0x31) [0x844ab71]
   #2 /usr/sbin/smbd() [0x83db76c]
   #3 /usr/lib/libtalloc.so.2(+0x32ef) [0xf75692ef]
   #4 /usr/sbin/smbd() [0x814c056]
   #5 /usr/sbin/smbd(create_file_default+0xfe) [0x814de4e]
   #6 /usr/sbin/smbd() [0x8190159]
   #7 /usr/sbin/smbd(smb_vfs_call_create_file+0xab) [0x815410b]
   #8 /usr/lib/samba/vfs/acl_xattr.so(+0x3346) [0xf70a1346]
   #9 /usr/sbin/smbd(smb_vfs_call_create_file+0xab) [0x815410b]
   #10 /usr/sbin/smbd(reply_ntcreate_and_X+0x269) [0x81150a9]
   #11 /usr/sbin/smbd() [0x8164ca9]
   #12 /usr/sbin/smbd() [0x81685c9]
   #13 /usr/sbin/smbd() [0x81689ac]
   #14 /usr/sbin/smbd(run_events_poll+0x392) [0x845a472]
   #15 /usr/sbin/smbd(smbd_process+0x9f9) [0x81681d9]
   #16 /usr/sbin/smbd() [0x87041dc]
   #17 /usr/sbin/smbd(run_events_poll+0x392) [0x845a472]
   #18 /usr/sbin/smbd() [0x845a8d7]
   #19 /usr/lib/libtevent.so.0(_tevent_loop_once+0x9b) [0xf755d73b]
   #20 /usr/sbin/smbd(main+0x11f0) [0x8705740]
   #21 /lib/i686/cmov/libc.so.6(__libc_start_main+0xe5) [0xf73d4e15]
   #22 /usr/sbin/smbd() [0x80e53a1]
[2016/07/17 13:49:52.623172,  0] lib/fault.c:372(dump_core)
  dumping core in /var/log/samba/cores/smbd

Once I figured that out I hunted down and deleted the crashplan failed upgrades that filled up my /, and now all is well.