Date: Tue, 18 Feb 2014 14:18:15 +0100 From: Jeremie Le Hen <jlh@FreeBSD.org> To: Andriy Gapon <avg@FreeBSD.org> Cc: freebsd-current@FreeBSD.org Subject: Re: panic: LK_RETRY set with incompatible flags (0x200400) or an error occured (11) Message-ID: <20140218131815.GF3783@caravan.chchile.org> In-Reply-To: <52FF59B8.1080206@FreeBSD.org> References: <20140210205607.GA3783@caravan.chchile.org> <52F94923.60102@FreeBSD.org> <20140211093529.GB3783@caravan.chchile.org> <20140214191858.GC3783@caravan.chchile.org> <52FF59B8.1080206@FreeBSD.org>
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On Sat, Feb 15, 2014 at 02:12:40PM +0200, Andriy Gapon wrote:
> on 14/02/2014 21:18 Jeremie Le Hen said the following:
> > I've just got another occurence of the exact same panic. Any clue how
> > to debug this?
>
> Could you please obtain *vp from frame 12 ?
Sure:
$1 = {v_tag = 0xffffffff815019a5 "zfs", v_op = 0xffffffff815164a0,
v_data = 0xfffff80010dcb2e0, v_mount = 0xfffff80010dcd660,
v_nmntvnodes = {tqe_next = 0xfffff80010dc7ce8,
tqe_prev = 0xfffff80010dcd6c0}, v_un = {vu_mount = 0x0,
vu_socket = 0x0, vu_cdev = 0x0, vu_fifoinfo = 0x0},
v_hashlist = {le_next = 0x0, le_prev = 0x0}, v_cache_src = {
lh_first = 0xfffff8005aeefcb0}, v_cache_dst = {tqh_first = 0x0,
tqh_last = 0xfffff80010dc8050}, v_cache_dd = 0x0, v_lock = {
lock_object = {lo_name = 0xffffffff815019a5 "zfs",
lo_flags = 117112832, lo_data = 0, lo_witness = 0x0},
lk_lock = 18446735277920538624, lk_exslpfail = 0, lk_timo = 51,
lk_pri = 96}, v_interlock = {lock_object = {
lo_name = 0xffffffff80b46085 "vnode interlock",
lo_flags = 16973824, lo_data = 0, lo_witness = 0x0},
mtx_lock = 4}, v_vnlock = 0xfffff80010dc8068, v_actfreelist = {
tqe_next = 0x0, tqe_prev = 0xfffff80010dc7da8}, v_bufobj = {
bo_lock = {lock_object = {
lo_name = 0xffffffff80b4e613 "bufobj interlock",
lo_flags = 86179840, lo_data = 0, lo_witness = 0x0},
rw_lock = 1}, bo_ops = 0xffffffff80e2d440,
bo_object = 0xfffff800a30bbd00, bo_synclist = {le_next = 0x0,
le_prev = 0x0}, bo_private = 0xfffff80010dc8000,
__bo_vnode = 0xfffff80010dc8000, bo_clean = {bv_hd = {
tqh_first = 0x0, tqh_last = 0xfffff80010dc8120}, bv_root = {
pt_root = 0}, bv_cnt = 0}, bo_dirty = {bv_hd = {
tqh_first = 0x0, tqh_last = 0xfffff80010dc8140}, bv_root = {
pt_root = 0}, bv_cnt = 0}, bo_numoutput = 0, bo_flag = 0,
bo_bsize = 131072}, v_pollinfo = 0x0, v_label = 0x0,
v_lockf = 0x0, v_rl = {rl_waiters = {tqh_first = 0x0,
tqh_last = 0xfffff80010dc8188}, rl_currdep = 0x0},
v_cstart = 0, v_lasta = 0, v_lastw = 0, v_clen = 0, v_holdcnt = 7,
v_usecount = 6, v_iflag = 512, v_vflag = 1, v_writecount = 0,
v_hash = 3, v_type = VDIR}
> The problem seems to be happening in this piece of ZFS code:
> if (cnp->cn_flags & ISDOTDOT) {
> ltype = VOP_ISLOCKED(dvp);
> VOP_UNLOCK(dvp, 0);
> }
> ZFS_EXIT(zfsvfs);
> error = vn_lock(*vpp, cnp->cn_lkflags);
> if (cnp->cn_flags & ISDOTDOT)
> vn_lock(dvp, ltype | LK_RETRY);
>
> ltype is apparently LK_SHARED and the assertion is apparently triggered by
> EDEADLK error. The error can occur only if a thread tries to obtain a lock in a
> shared mode when it already has the lock exclusively.
> My only explanation of how this could happen is that dvp == *vpp and cn_lkflags
> is LK_EXCLUSIVE. In other words, this is a dot-dot lookup that results in the
> same vnode. I think that this is only possible if dvp is the root vnode.
> I am not sure if my theory is correct though.
> Also, I am not sure if zfs_lookup() should be prepared to handle such a lookup
> or if this kind of lookup should be handled by upper/other layers. In this case
> these would be VFS lookup code and nullfs code.
--
Jeremie Le Hen
Scientists say the world is made up of Protons, Neutrons and Electrons.
They forgot to mention Morons.
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