[Bug 14610] New: Lockup in kernel 5.10 when copying large folder

[samba-bugs@samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=14610

            Bug ID: 14610
           Summary: Lockup in kernel 5.10 when copying large folder
           Product: CifsVFS
           Version: 5.x
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: kernel fs
          Assignee: sfrench@samba.org
          Reporter: wheybags@wheybags.com
        QA Contact: cifs-qa@samba.org
  Target Milestone: ---

Created attachment 16384
  --> https://bugzilla.samba.org/attachment.cgi?id=16384&action=edit
server side config file

I have been having an issue with CIFS mounts when running kernel 5.10 on the
client (using the 5.10 build from
https://wiki.ubuntu.com/Kernel/MainlineBuilds).

When doing a lot of IO in a file copy tool I'm writing, the mount would lock
up, and calls to open() would hang, sometimes form multiple seconds, and in a
few cases indefinitely (I left it for multiple minutes). Accessing the share
from a separate process (eg, running ls in a separate shell) would normally
work fine, but on a few occasions the share locked up completely and wouldn't
re-mount until I rebooted. When the lockups happen I get the following in
dmesg, sometimes just once, and sometimes repeating thousands of times:

Jan  2 00:13:50 pooka kernel: [ 9548.025373] CIFS: VFS: \\192.168.1.1 No task
to wake, unknown frame received! NumMids 1
   29 Jan  2 00:13:50 pooka kernel: [ 9548.025380] 00000000: 424d53fe 00000040
00000000 00000012  .SMB@...........
   30 Jan  2 00:13:50 pooka kernel: [ 9548.025382] 00000010: 00000001 00000000
ffffffff ffffffff  ................
   31 Jan  2 00:13:50 pooka kernel: [ 9548.025383] 00000020: 00000000 00000000
00000000 00000000  ................
   32 Jan  2 00:13:50 pooka kernel: [ 9548.025384] 00000030: 00000000 00000000
00000000 00000000  ................

The kernel messages will show up for me by running a copy of a large directory
using standard cp, as well. The problem is not present when running kernel 5.8
(stock for my distro).

The machines are connected directly via ethernet, I am pretty certain that
connection loss is not part of the problem. The client is running Ubuntu 20.10,
with kernel 5.10, and the client is stock Ubuntu 20.04 LTS.

Here's the mount line from /etc/fstab on the client:
//192.168.1.1/allfiles                       /files_zfs cifs
rw,relatime,cache=strict,user=guest,pass=,uid=0,file_mode=0755,dir_mode=0755,uid=1000,gid=1000
0 0

I have attached the server side config file.

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