Re: panic: LK_RETRY set with incompatible flags

Andriy Gapon wrote:
> on 31/01/2013 15:29 Sergey Kandaurov said the following:
> > Hi.
> >
> > Got this assertion on idle NFS server while `ls -la /.zfs/shares/'
> > issued on NFS client.
> > kern/vfs_vnops.c:_vn_lock()
> >                 KASSERT((flags & LK_RETRY) == 0 || error == 0,
> >                     ("LK_RETRY set with incompatible flags (0x%x) or
> > an error occured (%d)",
> >
> > panic: LK_RETRY set with incompatible flags (0x200400) or an error
> > occured (11)
> >
> > What does that mean and how is it possible? As you can see, both
> > parts
> > of assertion failed.
> > 11 is EDEADLK
> > 0x200400: LK_RETRY & LK_UPGRADE
> 
> LK_SHARED, not LK_UPGRADE.
> Apparently the thread already holds an exlusive lock on the vnode,
> which you
> confirm below.
> 
> 
> > Tracing pid 2943 tid 101532 td 0xfffffe004f5b7000
> > kdb_enter() at kdb_enter+0x3e/frame 0xffffff848e45ef50
> > vpanic() at vpanic+0x147/frame 0xffffff848e45ef90
> > kassert_panic() at kassert_panic+0x136/frame 0xffffff848e45f000
> > _vn_lock() at _vn_lock+0x70/frame 0xffffff848e45f070
> > zfs_lookup() at zfs_lookup+0x392/frame 0xffffff848e45f100
> > zfs_freebsd_lookup() at zfs_freebsd_lookup+0x6d/frame
> > 0xffffff848e45f240
> > VOP_CACHEDLOOKUP_APV() at VOP_CACHEDLOOKUP_APV+0xc2/frame
> > 0xffffff848e45f260
> > vfs_cache_lookup() at vfs_cache_lookup+0xcf/frame 0xffffff848e45f2b0
> > VOP_LOOKUP_APV() at VOP_LOOKUP_APV+0xc2/frame 0xffffff848e45f2d0
> > lookup() at lookup+0x548/frame 0xffffff848e45f350
> > nfsvno_namei() at nfsvno_namei+0x1a5/frame 0xffffff848e45f400
> > nfsrvd_lookup() at nfsrvd_lookup+0x13a/frame 0xffffff848e45f6b0
> > nfsrvd_dorpc() at nfsrvd_dorpc+0xca5/frame 0xffffff848e45f8a0
> > nfssvc_program() at nfssvc_program+0x482/frame 0xffffff848e45fa00
> > svc_run_internal() at svc_run_internal+0x1e9/frame
> > 0xffffff848e45fba0
> > svc_thread_start() at svc_thread_start+0xb/frame 0xffffff848e45fbb0
> > fork_exit() at fork_exit+0x84/frame 0xffffff848e45fbf0
> > fork_trampoline() at fork_trampoline+0xe/frame 0xffffff848e45fbf0
> > --- trap 0xc, rip = 0x800883e9a, rsp = 0x7fffffffd488, rbp =
> > 0x7fffffffd730 ---
> >
> > db> show lockedvnods
> > Locked vnodes
> >
> > 0xfffffe02e21b11d8: tag zfs, type VDIR
> >     usecount 4, writecount 0, refcount 4 mountedhere 0
> >     flags (VI_ACTIVE)
> >     v_object 0xfffffe02d9f2eb40 ref 0 pages 0
> >     lock type zfs: EXCL by thread 0xfffffe004f5b7000 (pid 2943,
> >     nfsd,
> > tid 101532)
> >
> >
> >
I just took a look at zfs_vnops.c and I am probably missing something,
but I can't see how this ever worked for a lookup of ".." when at the
root (unless ZFS doesn't do the ".." is the current directory when at
the root).

Here's the code snippet:
1442 	if (error == 0 && (nm[0] != '.' || nm[1] != '\0')) {
1443 	int ltype = 0;
1444 	
1445 	if (cnp->cn_flags & ISDOTDOT) {
1446 	        ltype = VOP_ISLOCKED(dvp);
1447            VOP_UNLOCK(dvp, 0);
1448 	}
1449 	ZFS_EXIT(zfsvfs);
1450 	error = zfs_vnode_lock(*vpp, cnp->cn_lkflags);
1451 	if (cnp->cn_flags & ISDOTDOT)
1452 	        vn_lock(dvp, ltype | LK_RETRY);
1453 	if (error != 0) {
1454 	        VN_RELE(*vpp);
1455 	        *vpp = NULL;
1456 	        return (error);
1457 	} 

Maybe line# 1451 should be changed to:
        if ((cnp->cn_flags & ISDOTDOT) && *vpp != dvp)

I'm not at all familiar with ZFS, so I've probably way
off the mark on this, rick
ps: I hope kib and jhb don't mind being added as cc's, since
    they are familiar with this stuff, although maybe not ZFS
    specifics.

> 
> 
> --
> Andriy Gapon
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