[LU-14713] Process hung with waiting for mmap_sem

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.15.0
• Affects Version/s: Lustre 2.12.7, Lustre 2.12.8
• Severity: 3
• Assignee: Zhenyu Xu
• Reporter: Zhenyu Xu

Description

Write and Truncate IO will serialized on ll_trunc_sem::ll_trunc_{readers|waiters}, if one process quit abruptly (be killed), the other will keep waiting for the semaphore (task state be set as TASK_INTERRUPTIBLE):

 INFO: task a.out:109684 blocked for more than 120 seconds.
      Tainted: G          IOE    --------- -  - 4.18.0-240.15.1.el8_3.x86_64 #1
 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 Call Trace:
 __schedule+0x2a6/0x700
 schedule+0x38/0xa0
 trunc_sem_down_read+0xa6/0xb0 [lustre]
 vvp_io_write_start+0x107/0xb80 [lustre]
 cl_io_start+0x59/0x110 [obdclass]
 cl_io_loop+0x9a/0x1e0 [obdclass]
 ll_file_io_generic+0x380/0xb10 [lustre]
 ll_file_write_iter+0x136/0x5a0 [lustre]
 new_sync_write+0x124/0x170
 vfs_write+0xa5/0x1a0
 ksys_write+0x4f/0xb0
 do_syscall_64+0x5b/0x1a0

Issue Links

• is related to: LU-15397 LustreError: 4585:0:(llite_mmap.c:61:our_vma()) ASSERTION( !down_write_trylock(&mm->mmap_sem) ) failed