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Date:      Fri, 31 May 2024 13:11:20 -0700
From:      Rick Macklem <rick.macklem@gmail.com>
To:        J David <j.david.lists@gmail.com>
Cc:        FreeBSD FS <freebsd-fs@freebsd.org>
Subject:   Re: NFSv4 hangs on 13.3
Message-ID:  <CAM5tNy7YSTDwVm_oMcu=1PqRyXtTmvzTF058nd1WCXyCHwrtTQ@mail.gmail.com>
In-Reply-To: <CABXB=RTH6s25EMQzDbg8WPr1hKtjKOJGVh3no0TFcNC=ufwXCw@mail.gmail.com>
References:  <CABXB=RTH6s25EMQzDbg8WPr1hKtjKOJGVh3no0TFcNC=ufwXCw@mail.gmail.com>

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On Fri, May 31, 2024 at 12:39=E2=80=AFPM J David <j.david.lists@gmail.com> =
wrote:
>
> In an attempt to narrow down the problems we have with NFS v4.2, we've
> set up a FreeBSD 13.3 server that mirrors some read-only data from our
> Linux NFS servers.
>
> We are still observing occasional hangs on the FreeBSD 13.3 client machin=
es.
>
> When these hangs occur, anything that touches the mountpoint
> (including "umount -N") hangs indefinitely. There is nothing in dmesg.
>
> The only even slightly informative data I could gather is an "ls
> /mount/point" kstack:
>
> $ sudo procstat -kk 94676
>   PID    TID COMM                TDNAME              KSTACK
> 94676 976876 ls                  -                   mi_switch+0xbf
> sleeplk+0xea lockmgr_slock_hard+0x3a5 nfs_lock+0x29 vop_sigdefer+0x2a
> _vn_lock+0x47 vfs_cache_root+0x9d vfs_root_sigdefer+0x35 lookup+0x88a
> namei+0x24a kern_statat+0xf8 sys_fstatat+0x27 amd64_syscall+0x110
> fast_syscall_common+0xf8
>
> During this time, the NFS server continues serving other clients, and
> the affected client can access other NFS servers without hanging.
>
> The "nfsstat -m" for this mountpoint looks like this:
>
> nfsv4,minorversion=3D2,oneopenown,tcp,resvport,nconnect=3D1,hard,cto,nolo=
ckd,sec=3Dsys,acdirmin=3D3,acdirmax=3D60,acregmin=3D5,acregmax=3D60,nametim=
eo=3D60,negnametimeo=3D60,rsize=3D65536,wsize=3D65536,readdirsize=3D65536,r=
eadahead=3D1,wcommitsize=3D16777216,timeout=3D120,retrans=3D2147483647
>
> with these mount flags in /etc/fstab:
>
> ro,nfsv4,minorversion=3D2,tcp,nosuid,noatime,nolockd,oneopenown
>
> Is there anything more we can do to help identify this issue?
Collect the output of:
# ps axHl
and
# procstat -kk -a

What you show above is just a thread waiting for a lock on an NFS vnode.
What we need to figure out is what thread is holding the lock on that vnode
while waiting for something else.

rick

>
> Thanks for any advice!
>



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