osd_scrub_setup() uses regular read/write which updates procfs stats. so the stats must be initialized for OI scrub. otherwise:
[ 35.389637] BUG: spinlock bad magic on CPU#0, mount.lustre/5948
[ 35.399328] lock: 0xffff8800b9f28688, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
[ 35.399634] CPU: 0 PID: 5948 Comm: mount.lustre Tainted: P OE ------------ 3.10.0-debug #2
[ 35.410877] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[ 35.411165] 0000000000000000 0000000062ba1829 ffff8802ff6df798 ffffffff816fd3e4
[ 35.411886] ffff8802ff6df7b8 ffffffff816fd472 ffff8800b9f28688 ffffffff81aa1a78
[ 35.412541] ffff8802ff6df7d8 ffffffff816fd498 ffff8800b9f28688 0000000000000001
[ 35.413900] Call Trace:
[ 35.414871] [<ffffffff816fd3e4>] dump_stack+0x19/0x1b
[ 35.415782] [<ffffffff816fd472>] spin_dump+0x8c/0x91
[ 35.416723] [<ffffffff816fd498>] spin_bug+0x21/0x26
[ 35.417674] [<ffffffff8138ec10>] do_raw_spin_lock+0x130/0x150
[ 35.418664] [<ffffffff81706249>] _raw_spin_lock+0x49/0x50
[ 35.419697] [<ffffffffa0377c07>] ? lprocfs_oh_tally+0x17/0x40 [obdclass]
[ 35.420682] [<ffffffffa0377c07>] lprocfs_oh_tally+0x17/0x40 [obdclass]
[ 35.421512] [<ffffffffa116d81b>] record_start_io.part.13+0x2b/0x40 [osd_zfs]
[ 35.422322] [<ffffffffa116df1d>] osd_read+0xfd/0x2b0 [osd_zfs]
[ 35.423125] [<ffffffffa039f1e4>] dt_read+0x14/0x50 [obdclass]
[ 35.423978] [<ffffffffa03c355f>] scrub_file_load+0x4f/0x410 [obdclass]