вт, 12 нояб. 2019 г. в 11:34, Frank Sorenson <sorenson@redhat.com>:
>
> If a process opening a file is killed while waiting for a SMB2_CREATE
> response from the server, the response may not be handled by the client,
> leaking an open file handle on the server.
>

Thanks for reporting the problem.

> This can be reproduced with the following:
>
> # mount //vm3/user1 /mnt/vm3 -overs=3,sec=ntlmssp,credentials=/root/.user1_smb_creds
> # cd /mnt/vm3
> # echo foo > foo
>
> # for i in {1..100} ; do cat foo >/dev/null 2>&1 & sleep 0.0001 ; kill -9 $! ; done
>
> (increase count if necessary--100 appears sufficient to cause multiple leaked file handles)
>

This is a known problem and the client handles it by closing unmatched
opens (the one that don't have a corresponding waiting thread)
immediately. It is indicated by the message you observed: "Close
unmatched open".

>
> The client will stop waiting for the response, and will output
> the following when the response does arrive:
>
>     CIFS VFS: Close unmatched open
>
> on the server side, an open file handle is leaked.  If using samba,
> the following will show these open files:
>
>
> # smbstatus | grep -i Locked -A1000
> Locked files:
> Pid          Uid        DenyMode   Access      R/W        Oplock           SharePath   Name   Time
> --------------------------------------------------------------------------------------------------
> 25936        501        DENY_NONE  0x80        RDONLY     NONE             /home/user1   .   Tue Nov 12 12:29:24 2019
> 25936        501        DENY_NONE  0x80        RDONLY     NONE             /home/user1   .   Tue Nov 12 12:29:24 2019
> 25936        501        DENY_NONE  0x120089    RDONLY     LEASE(RWH)       /home/user1   foo   Tue Nov 12 12:29:24 2019
> 25936        501        DENY_NONE  0x120089    RDONLY     LEASE(RWH)       /home/user1   foo   Tue Nov 12 12:29:24 2019
> 25936        501        DENY_NONE  0x120089    RDONLY     LEASE(RWH)       /home/user1   foo   Tue Nov 12 12:29:24 2019
> 25936        501        DENY_NONE  0x120089    RDONLY     LEASE(RWH)       /home/user1   foo   Tue Nov 12 12:29:24 2019
> 25936        501        DENY_NONE  0x120089    RDONLY     LEASE(RWH)       /home/user1   foo   Tue Nov 12 12:29:24 2019
>

I tried it locally myself, it seems that we have another issue related
to interrupted close requests:

[1656476.740311] fs/cifs/file.c: Flush inode 0000000078729371 file
000000004d5f9348 rc 0
[1656476.740313] fs/cifs/file.c: closing last open instance for inode
0000000078729371
[1656476.740314] fs/cifs/file.c: CIFS VFS: in _cifsFileInfo_put as
Xid: 457 with uid: 1000
[1656476.740315] fs/cifs/smb2pdu.c: Close
[1656476.740317] fs/cifs/transport.c: signal is pending before sending any data

This will return -512 error to the upper layer but we do not save a
problematic handle somewhere to close it later. op->release() error
code is not being checked by VFS anyway.

We should do the similar thing as we do today for cancelled mids:
allocate "struct close_cancelled_open" and queue the lazy work to
close the handle.

I attached the patch implementing this idea. The patch handles the
interrupt errors in smb2_close_file which is called during close
system call. It fixed the problem in my setup. In the same time I
think I should probably move the handling to PDU layer function
SMB2_close() to handle *all* interrupted close requests including ones
closing temporary handles. I am wondering if anyone has thoughts about
it. Anyway, review of the patch is highly appreciated.

@Frank, could you please test the patch in your environment?

--
Best regards,
Pavel Shilovsky