repeatable ZFS panic: share->excl

[Attilio Rao]

2009/3/12, Anonymous <swell.k at gmail.com>:
> Tim Kientzle <kientzle at freebsd.org> writes:
>
>  > Peter Schuller wrote:
>  >>>   First problem I notice is a panic, which seems to occur every
>  >>> time 'tar' is used. Might be unrelated to tar, but it definately
>  >>> provokes it. Simply the tar command or a pkg_add causes it.
>  >>
>  >> See the "ZFS/extattr lockup"/"bsdtar lockup on current" threads from
>  >> the past handful of days.
>  >
>  > I think this may be a different problem.
>  > The earlier thread involved a ZFS bug that causes
>  > it to lock up if it receives a request to enumerate
>  > extended attributes on a file (via extattr_list_link
>  > system call).  Tar recently added support for
>  > backing up extended attributes.  I've disabled
>  > that support until this particular ZFS problem can
>  > be fixed.
>
>
> I guess you're wrong, it's same issue. Here is output from unmodified
>  kernel (r189728) under qemu which looks exactly as on that
>  screenshot. Perhaps, the panic is triggered by INVARIANTS.
>
>  # lsextattr -h user foo
>  shared lock of (lockmgr) zfs @ /usr/src/sys/kern/vfs_lookup.c:477
>  while exclusively locked from /usr/src/sys/modules/zfs/../../cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c:152
>  panic: share->excl
>  cpuid = 0
>  KDB: enter: panic
>  [thread pid 105 tid 100078 ]
>  Stopped at      kdb_enter+0x3d: movq    $0,0x662538(%rip)
>
>  db> bt
>  Tracing pid 105 tid 100078 td 0xffffff00015bea80
>  kdb_enter() at kdb_enter+0x3d
>  panic() at panic+0x17b
>  witness_checkorder() at witness_checkorder+0x16e
>  __lockmgr_args() at __lockmgr_args+0xd1b
>  vop_stdlock() at vop_stdlock+0x39
>  VOP_LOCK1_APV() at VOP_LOCK1_APV+0x9b
>  _vn_lock() at _vn_lock+0x57
>  lookup() at lookup+0xf4
>  namei() at namei+0x545
>  zfs_listextattr() at zfs_listextattr+0x18c
>  VOP_LISTEXTATTR_APV() at VOP_LISTEXTATTR_APV+0xb5
>  extattr_list_vp() at extattr_list_vp+0x22a
>  extattr_list_link() at extattr_list_link+0xc3
>  syscall() at syscall+0x1e7
>  Xfast_syscall() at Xfast_syscall+0xab
>  --- syscall (439, FreeBSD ELF64, extattr_list_link), rip = 0x800692e4c, rsp = 0x7fffffffed08, rbp = 0x7fffffffede0 ---
>
>  db> show all locks
>  Process 105 (lsextattr) thread 0xffffff00015bea80 (100078)
>  exclusive lockmgr zfs (zfs) r = 0 (0xffffff0001581578) locked @ /usr/src/sys/modules/zfs/../../cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c:152
>  exclusive lockmgr zfs (zfs) r = 0 (0xffffff0001581a58) locked @ /usr/src/sys/kern/vfs_extattr.c:668
>
>  db> show lockedvnods
>  Locked vnodes
>
>  0xffffff00015819c0: tag zfs, type VREG
>     usecount 1, writecount 0, refcount 1 mountedhere 0
>     flags ()
>     v_object 0xffffff0001574898 ref 0 pages 0
>     lock type zfs: EXCL by thread 0xffffff00015bea80 (pid 105)
>  #0 0xffffffff80530568 at __lockmgr_args+0x758
>  #1 0xffffffff805c0fd9 at vop_stdlock+0x39
>  #2 0xffffffff808557db at VOP_LOCK1_APV+0x9b
>  #3 0xffffffff805dd6a7 at _vn_lock+0x57
>  #4 0xffffffff805c2f20 at extattr_list_vp+0xb0
>  #5 0xffffffff805c3173 at extattr_list_link+0xc3
>  #6 0xffffffff8080f227 at syscall+0x1e7
>  #7 0xffffffff807ec39b at Xfast_syscall+0xab
>
>  0xffffff00015814e0: tag zfs, type VDIR
>     usecount 1, writecount 0, refcount 1 mountedhere 0
>     flags ()
>     lock type zfs: EXCL by thread 0xffffff00015bea80 (pid 105)
>  #0 0xffffffff80530568 at __lockmgr_args+0x758
>  #1 0xffffffff805c0fd9 at vop_stdlock+0x39
>  #2 0xffffffff808557db at VOP_LOCK1_APV+0x9b
>  #3 0xffffffff805dd6a7 at _vn_lock+0x57
>  #4 0xffffffff8108405e at zfs_znode_cache_constructor+0x4e
>  #5 0xffffffff81085029 at zfs_znode_alloc+0x39
>  #6 0xffffffff81085915 at zfs_mknode+0x205
>  #7 0xffffffff810948f5 at zfs_make_xattrdir+0x155
>  #8 0xffffffff81095bc3 at zfs_get_xattrdir+0xd3
>  #9 0xffffffff810a4dbf at zfs_lookup+0x11f
>  #10 0xffffffff810a51d8 at zfs_listextattr+0x128
>  #11 0xffffffff80853255 at VOP_LISTEXTATTR_APV+0xb5
>  #12 0xffffffff805c309a at extattr_list_vp+0x22a
>  #13 0xffffffff805c3173 at extattr_list_link+0xc3
>  #14 0xffffffff8080f227 at syscall+0x1e7
>  #15 0xffffffff807ec39b at Xfast_syscall+0xab

Could you please re-enable the extended attributes on bsdtar, try this
patch and report to me?:
http://www.freebsd.org/~attilio/zfs_vnops.diff

(sorry if it is untested but I just don't have any ZFS machine).
Actually, I think the problem is that zfs_lookup() doesn't get the
correct handover once the extended attributes directory vnode is
retrieved.

Thanks,
Attilio


-- 
Peace can only be achieved by understanding - A. Einstein