Greetings,

I got the below dmesg and the first bad commit is

commit 84550b9356af50c7cbd6b6ce6e8fd06585eebf14
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Sun Sep 29 22:06:07 2013 -0400

    RCU'd vfsmounts
    
    _very_ preliminary, barely tested.
    
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

[    3.509455] power_supply test_battery: prop VOLTAGE_NOW=3300
Kernel tests: Boot OK!
[   70.923628] ------------[ cut here ]------------
[   70.928604] WARNING: CPU: 1 PID: 479 at fs/dcache.c:385 d_lru_del+0x15f/0x190()
[   70.933837] Modules linked in:
[   70.951217] CPU: 1 PID: 479 Comm: umount Not tainted 3.12.0-00649-g32a440b #89
[   70.956272] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   70.960968]  ffffffff cca87e04 c1c05539 00000000 00000000 00000181 cca87e34 c1064306
[   70.966287]  c1ec447c 00000001 000001df c1ed6158 00000181 c11d221f c11d221f 00000001
[   70.971684]  cea83e80 00000001 cca87e44 c10643c2 00000009 00000000 cca87e58 c11d221f
[   70.977076] Call Trace:
[   70.981446]  [<c1c05539>] dump_stack+0x7d/0xb0
[   70.986142]  [<c1064306>] warn_slowpath_common+0x96/0xb0
[   70.990978]  [<c11d221f>] ? d_lru_del+0x15f/0x190
[   70.995755]  [<c11d221f>] ? d_lru_del+0x15f/0x190
[   71.000432]  [<c10643c2>] warn_slowpath_null+0x22/0x30
[   71.005244]  [<c11d221f>] d_lru_del+0x15f/0x190
[   71.009871]  [<c11d27ff>] umount_collect+0x14f/0x190
[   71.014502]  [<c1c139a2>] ? _raw_spin_lock+0x42/0xb0
[   71.019072]  [<c11d3847>] d_walk+0xc7/0x3d0
[   71.023599]  [<c11d26b0>] ? dentry_lru_del+0x70/0x70
[   71.028535]  [<c11d5d8b>] shrink_dcache_for_umount+0x8b/0x150
[   71.033510]  [<c11b4477>] generic_shutdown_super+0xc7/0x1a0
[   71.038858]  [<c11b480a>] kill_litter_super+0x3a/0x50
[   71.043563]  [<c11b4a95>] deactivate_locked_super+0x45/0x70
[   71.048629]  [<c11b5e16>] deactivate_super+0x96/0xb0
[   71.053511]  [<c11df6e6>] mntput_no_expire+0x1d6/0x200
[   71.058174]  [<c11e0d41>] SyS_umount+0x121/0x5e0
[   71.063860]  [<c11e121e>] SyS_oldumount+0x1e/0x20
[   71.068699]  [<c1c140ff>] syscall_call+0x7/0xb
[   71.073363] ---[ end trace 6b92dd3d08e2681d ]---
[   71.078672] ------------[ cut here ]------------

git bisect start 32a440b38c2b6f2f927b8e294e4877fe505f9653 5e01dc7b26d9f24f39abace5da98ccbd6a5ceb52 --
git bisect good 1e7a6935bccc8d16596b2f72d4162eadb0a5f2d0  # 10:35     17+      3  Merge 'tip/perf/core' into devel-roam-i386-201311072347
git bisect good 6f7dbe7290a3c2af9ccf75c7e219dfc1ee762b05  # 11:04     17+      0  Merge 'at91/nfe/at91-3.14-cleanup+test-new' into devel-roam-i386-201311072347
git bisect  bad 5d4c247511b3030ca14d7b2d12e2f206bbccb7d1  # 11:19      0-      4  locks: introduce new FL_DELEG lock flag
git bisect  bad 84550b9356af50c7cbd6b6ce6e8fd06585eebf14  # 11:37      0-      4  RCU'd vfsmounts
git bisect good 6339dab869e07a81abd22970696dde6febee094a  # 11:55     20+      0  do_remount(): pull touch_mnt_namespace() up
git bisect good 474279dc0f7745124fc76b474c8dc1294f8e87ce  # 12:10     20+      1  split __lookup_mnt() in two functions
git bisect good baa40671d3e3b590a33b2c0e022db61cbebf5c00  # 12:31     20+      0  autofs4: make freeing sbi rcu-delayed
git bisect good 1dcddd4abd2c6df7f28928ad5cafa4a1cd20030b  # 12:43     20+      0  ncpfs: rcu-delay unload_nls() and freeing ncp_server
git bisect good dd3e2c55a45fe75f3213b17b74f9a32380f4e84b  # 12:51     20+      0  fuse: rcu-delay freeing fuse_conn
git bisect good dd3e2c55a45fe75f3213b17b74f9a32380f4e84b  # 12:54     60+      0  fuse: rcu-delay freeing fuse_conn
git bisect  bad 32a440b38c2b6f2f927b8e294e4877fe505f9653  # 12:54      0-     19  Merge 'vfs/for-next' into devel-roam-i386-201311072347
git bisect good 6c86ae2928f9e4cbf0d5844f5fcfd549e3450b8c  # 13:28     60+      4  Merge tag 'ftrace-urgent-3.12-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Thanks,
Fengguang