VNOP_FSYNC: mutex_enter: locking against myself!"@spl-mutex.c:108

[lundman]

Large rsync (Copying "/" to ZFS) produced:

panic(cpu 0 caller 0xffffff7f86bdf4a8): "mutex_enter: locking against myself!"@spl-mutex.c:108
Backtrace (CPU 0), Frame : Return Address
0xffffff804ab13360 : 0xffffff800541d626 mach_kernel : _panic + 0xc6
0xffffff804ab133d0 : 0xffffff7f86bdf4a8 net.lundman.spl : _spl_mutex_enter + 0x78
0xffffff804ab133f0 : 0xffffff7f86cc4614 net.lundman.zfs : _zfs_zget + 0x74
0xffffff804ab13490 : 0xffffff7f86caf1ed net.lundman.zfs : _zfs_get_data + 0x7d
0xffffff804ab13540 : 0xffffff7f86ccc0a6 net.lundman.zfs : _zil_lwb_commit + 0x356
0xffffff804ab135d0 : 0xffffff7f86cca128 net.lundman.zfs : _zil_commit_writer + 0x128
0xffffff804ab13620 : 0xffffff7f86cc9f87 net.lundman.zfs : _zil_commit + 0x137
0xffffff804ab13650 : 0xffffff7f86cb2ae0 net.lundman.zfs : _zfs_fsync + 0x110
0xffffff804ab136a0 : 0xffffff7f86cb9dfe net.lundman.zfs : _zfs_vnop_fsync + 0x6e
0xffffff804ab136e0 : 0xffffff8005511f3f mach_kernel : _VNOP_FSYNC + 0x2f
0xffffff804ab13710 : 0xffffff80054f1583 mach_kernel : _vflush + 0x673
0xffffff804ab13760 : 0xffffff80054f0cd1 mach_kernel : _vnode_rele_ext + 0x351
0xffffff804ab137a0 : 0xffffff80054f7ac6 mach_kernel : _vfs_addtrigger + 0x2a6
0xffffff804ab137d0 : 0xffffff80054efa5e mach_kernel : _vnode_create + 0x15e
0xffffff804ab13890 : 0xffffff7f86cbce9c net.lundman.zfs : _zfs_znode_getvnode + 0x20c
0xffffff804ab13930 : 0xffffff7f86cc3260 net.lundman.zfs : _zfs_znode_alloc + 0x760
0xffffff804ab13b20 : 0xffffff7f86cc4849 net.lundman.zfs : _zfs_zget + 0x2a9
0xffffff804ab13bc0 : 0xffffff7f86cbb780 net.lundman.zfs : _zfs_vnop_readdirattr + 0x5f0
0xffffff804ab13e00 : 0xffffff8005513246 mach_kernel : _VNOP_READDIRATTR + 0x56
0xffffff804ab13e60 : 0xffffff8005501f1a mach_kernel : _getdirentriesattr + 0x2da
0xffffff804ab13f50 : 0xffffff80057e16aa mach_kernel : _unix_syscall64 + 0x20a
0xffffff804ab13fb0 : 0xffffff80054ce9c3 mach_kernel : _hndl_unix_scall64 + 0x13

Pretty clear that we call zget which allocates a new vnode which trigger a vflush which triggers a zil_commit which has to call zget.

Quite similar to the reclaim issue, and can be solved the same. This explains why MacZFS has logic to test for this case finally.

[lundman]

fc7b82d

Test if we are already locked in zget.

This takes a different approach to MacZFS, who passes a value from zfs_get_data to avoid locks.