Hi everyone:
I create a target using fileio as the backend storage on ARM64 server. The initiator reported some errors showed bellow  while perform iozone test.

[178444.145679]  connection14:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4339462894, last ping 4339464146, now 4339465400
[178444.145706]  connection14:0: detected conn error (1011)
[178469.674313]  connection14:0: detected conn error (1020)
[178504.420979]  connection14:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4339477953, last ping 4339479204, now 4339480456
[178504.421001]  connection14:0: detected conn error (1011)
[178532.064262]  connection14:0: detected conn error (1020)
[178564.584087]  connection14:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4339492980, last ping 4339494232, now 4339495484
..............................

I try to trace the function call of target iscsi. Then, I found the  receiving  thread of target iscsi blocked at fd_execute_sync_cache -> vfs_fsync_range. Further, vfs_fsync_range may takes more than 10 seconds to return,while initiator Ping timeout would happened after 5 seconds.   vfs_fsync_range was call with the form vfs_fsync_range(fd_dev->fd_file, 0, LLONG_MAX, 1) every times  which means sync all device cache. 
So, is this a bug?
How  does Initiator send sync_cache scsi command? 
Does it need to sync all device cache at once?
Any reply would be thankful.