Ceph » CephFS

1. reproduce the scene as shown below：

(1) step 1:
Open the terminal_1, and
Prepare the cmd: "killall -q -1 ceph-fuse" from /etc/logrotate.d/ceph-common

(2) step 2:
Open the terminal_2 and
run the cmd: "ceph-fuse -m monip:port mountpoint"

(3) step 3:
Switch to terminal_1 immediately, and
Keep running the cmd: "killall -q -1 ceph-fuse"

2. You will find the following anomalies:
The ceph-fuse process has abnormal exit, and there is an Uninterruptible Sleep mount process,just like the following:

root@***:~#  ps -aux  | grep mount
root      271493  0.0  0.0  26484  1252 ?        D    Jun28   0:00 mount -i -o remount mountpoint

The ceph-fuse abnormal exit logs as bellow:

7fe99f769680  0 pidfile_write: ignore empty --pid-file
7fe99f769680 -1 init, newargv = 0x5583ca2243a0 newargc=9
7fe9952d3700  1 client.63156060 handle_mds_map epoch 29934
7fe999adc700 -1 received  signal: Hangup pid: 1062451 from  PID: 1062486 task name: killall -q -1 ceph-fuse  UID: 0

7fe9912cb700  1 client.63156060 using remount_cb
7fe990aca700 -1 fuse_ll: do_init: safe_write failed with error (32) Broken pipe
7fe990aca700 -1 fuse_ll: do_init: safe_write failed with error (32) Broken pipe
7fe990aca700 -1 *** Caught signal (Aborted) **
  in thread 7fe990aca700 thread_name:ceph-fuse

 1: (()+0x6ddf14) [0x5583c1086f14]
 2: (()+0x110e0) [0x7fe99d7fb0e0]
 3: (gsignal()+0xcf) [0x7fe99c5affff]
 4: (abort()+0x16a) [0x7fe99c5b142a]
 5: (()+0x1ed03b) [0x5583c0b9603b]
 6: (()+0x1536c) [0x7fe99f0c736c]
 7: (()+0x165a1) [0x7fe99f0c85a1]
 8: (()+0x12d48) [0x7fe99f0c4d48]
 9: (()+0x74a4) [0x7fe99d7f14a4]
 10: (clone()+0x3f) [0x7fe99c665d0f]
 NOTE: a copy of the executable, or `objdump -rdS <executable>` is needed to interpret this.

3. The reason
The SIGHUP signal handlers are not registered in parent ceph-fuse process.

more detailed explanation is as follows：
In the process of starting the ceph-fuse,if system just calls the logratote("killall -q -1 ceph-fuse ..") before the function of safe_read_exact in parent ceph-fuse process is complete,
it will cause the parent ceph-fuse process abnormal exit because of the parent process don't handle the SIGHUP signal,then it will lead to the child ceph-fuse process assert because of the function call of safe_write in do_init,then it will lead the system call of "mount -i -o remount" in remount_cb become Uninterruptible Sleep process.

4.solution

Register the SIGHUP signal handlers in parent ceph-fuse process.