Re: git: 8ef0c11e7ce7 - main - nfsclient: upgrade vnode lock in VOP_OPEN()/VOP_CLOSE() if we need to flush buffers

On 2021-Nov-16 17:14:55 +0000, Konstantin Belousov <kib@FreeBSD.org> wrote:
>    nfsclient: upgrade vnode lock in VOP_OPEN()/VOP_CLOSE() if we need to flush buffers
>    
>    VOP_FSYNC() asserts that the vnode is exclusively locked for NFS.
>    If we try to execute file with recently modified content, the assert is
>    triggered.

I have a diskless arm64 system configured with swap over NFS and I'm
now consistently getting a panic during shutdown.  I haven't
specificially confirmed that it's this commit but the content is
suggestive.

panic: upgrade of unlocked lock (lockmgr) nfs @ /usr/src/sys/fs/nfsclient/nfs_clvnops.c:855
cpuid = 3
time = 1637166551
KDB: stack backtrace:
db_trace_self() at db_trace_self
db_trace_self_wrapper() at db_trace_self_wrapper+0x30
vpanic() at vpanic+0x178
panic() at panic+0x44
witness_upgrade() at witness_upgrade+0x104
lockmgr_upgrade() at lockmgr_upgrade+0x164
nfs_lock() at nfs_lock+0x2c
vop_sigdefer() at vop_sigdefer+0x30
_vn_lock() at _vn_lock+0x54
nfs_close() at nfs_close+0xc8
vop_sigdefer() at vop_sigdefer+0x30
VOP_CLOSE_APV() at VOP_CLOSE_APV+0x2c
swapdev_close() at swapdev_close+0x3c
swapoff_one() at swapoff_one+0x598
sys_swapoff() at sys_swapoff+0x12c
do_el0_sync() at do_el0_sync+0x498
handle_el0_sync() at handle_el0_sync+0x90
--- exception, esr 0x56000000

I presume this isn't intended.  Can you suggest where I should start
looking for the problem?

-- 
Peter Jeremy