Re: [PATCH 12/14] cifs: handle when server stops supporting multichannel

Shyam Prasad N
2023-11-09T13:49:35Z

On Thu, Nov 9, 2023 at 6:58 PM Paulo Alcantara <pc@manguebit.com> wrote:
>
> Shyam Prasad N <nspmangalore@gmail.com> writes:
>
> > On Thu, Nov 9, 2023 at 1:11 AM Paulo Alcantara <pc@manguebit.com> wrote:
> >>
> >> > and leaked server connections
> >> >
> >> > Display Internal CIFS Data Structures for Debugging
> >> > ---------------------------------------------------
> >> > CIFS Version 2.46
> >> > Features: DFS,FSCACHE,STATS2,DEBUG2,ALLOW_INSECURE_LEGACY,CIFS_POSIX,UPCALL(SPNEGO),XATTR,ACL,WITNESS
> >> > CIFSMaxBufSize: 16384
> >> > Active VFS Requests: 0
> >> >
> >> > Servers:
> >> > 1) ConnectionId: 0x70e Hostname: w22-root2.gandalf.test
> >> > ClientGUID: 44DAE383-3E91-3042-85FE-87D6F17298B7
> >> > Number of credits: 1,1,1 Dialect 0x210
> >> > Server capabilities: 0x300007
> >> > TCP status: 4 Instance: 77
> >> > Local Users To Server: 1 SecMode: 0x1 Req On Wire: 0 Net namespace: 4026531840
> >> > In Send: 0 In MaxReq Wait: 0
> >> > DFS leaf full path: \\W22-ROOT1.GANDALF.TEST\dfstest3\link10
> >> >
> >> > Sessions:
> >> > [NONE]
> >> > 2) ConnectionId: 0x706 Hostname: w22-root2.gandalf.test
> >> > ClientGUID: C8CF45E4-F70D-DF40-8821-0234A2E20DD4
> >> > Number of credits: 1,1,1 Dialect 0x210
> >> > Server capabilities: 0x300007
> >> > TCP status: 4 Instance: 81
> >> > Local Users To Server: 1 SecMode: 0x1 Req On Wire: 0 Net namespace: 4026531840
> >> > In Send: 0 In MaxReq Wait: 0
> >> > DFS leaf full path: \\W22-ROOT1.GANDALF.TEST\dfstest3\link6
> >> >
> >> > Sessions:
> >> > [NONE]
> >> > 3) ConnectionId: 0x6ae Hostname: w22-root1.gandalf.test
> >> > ClientGUID: AB059CDD-12FF-B94D-B30C-9E1928ACBA95
> >> > Number of credits: 1,1,1 Dialect 0x210
> >> > Server capabilities: 0x300007
> >> > TCP status: 4 Instance: 96
> >> > Local Users To Server: 1 SecMode: 0x1 Req On Wire: 0 Net namespace: 4026531840
> >> > In Send: 0 In MaxReq Wait: 0
> >> > DFS leaf full path: \\W22-ROOT1.GANDALF.TEST\dfstest3\link9
> >> >
> >> > Sessions:
> >> > [NONE]
> >> > ...
> >>
> >> I ended up with a simple reproducer for the above
> >>
> >> mount.cifs //srv/share /mnt/1 -o ...,echo_interval=10
> >> iptables -I INPUT -s $srvaddr -j DROP
> >> stat -f /mnt/1
> >> # check dmesg for "BUG: sleeping function called from invalid context"
> >> iptables -I INPUT -s $srvaddr -j ACCEPT
> >> stat -f /mnt/1
> >> umount /mnt/1
> >> # check /proc/fs/cifs/DebugData for leaked server connection
> >
> > Ack. I'll try and get a repro locally and debug this one.
>
> This should be related to patch 10/14 as you're taking an extra
> reference of @server over reconnect, and when the client reconnects and
> umount, that reference don't seem to be put afterwards.

The idea is that the reference is put in the reconnect worker.
I think the issue is that I don't drop the final reference if
cancel_delayed_work_sync was able to cancel a work.
Let me work on the updated patch.

Also, I found the reason for "BUG: sleeping function called from
invalid context". I've enabled CONFIG_DEBUG_ATOMIC_SLEEP in my test
config now.

--
Regards,
Shyam