Issue

ext4 ファイルシステムのマウントを解除すると shrink_dcache_for_umount_subtree() でパニックが発生します。

BUG:Dentry ffff88021dc61980{i=201b,n=.} still in use (24) [unmount of ext4 dm-2]
------------[ cut here ]------------
kernel BUG at fs/dcache.c:670!
invalid opcode:0000 [#1] SMP 
last sysfs file:/sys/devices/pci0000:00/0000:00:15.0/0000:03:00.0/local_cpus
CPU 0 
Modules linked in: ipv6 fuse dazuko(U) usb_spi(U) autofs4 nfs lockd fscache nfs_acl auth_rpcgss sunrpc vsock(U) uinput ppdev parport_pc parport e1000 sg microcode vmware_balloon vmci(U) i2c_piix4 i2c_core shpchp ext4 mbcache jbd2 sd_mod crc_t10dif sr_mod cdrom vmw_pvscsi pata_acpi ata_generic ata_piix dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]

Pid:22286, comm: umount Not tainted 2.6.32-220.17.1.el6.x86_64 #1 VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform
RIP:0010:[<ffffffff8118eba8>]  [<ffffffff8118eba8>] shrink_dcache_for_umount_subtree+0x2a8/0x2b0
RSP:0000:ffff880237af1de8  EFLAGS:00010296
RAX:0000000000000058 RBX: ffff88021dc61980 RCX:0000000000000000
RDX:0000000000000000 RSI:0000000000000046 RDI:0000000000000246
RBP: ffff880237af1e28 R08:000000000001072d R09:20666f20746e756f
R10:0000000000000001 R11:2820657375206e69 R12:0000000000000008
R13: ffffffff81a83ec0 R14: ffff8801ea1b5780 R15: ffff88021dc619e0
FS:00007f9502c21740(0000) GS:ffff880028200000(0000) knlGS:0000000000000000
CS:0010 DS:0000 ES:0000 CR0:000000008005003b
CR2:00000033bd406dd0 CR3:00000001a9897000 CR4:00000000000006f0
DR0:0000000000000000 DR1:0000000000000000 DR2:0000000000000000
DR3:0000000000000000 DR6:00000000ffff0ff0 DR7:0000000000000400
Process umount (pid:22286, threadinfo ffff880237af0000, task ffff8801c43a0ac0)
Stack:
 ffff880235b62270 ffff8802387a5500 ffffffff8105ea30 ffff880235b62000
<0> ffffffffa00ddfe0 ffffffff81c00340 ffff880235b62000 ffff8802366793c0
<0> ffff880237af1e48 ffffffff8118ebe6 0000000000000286 ffff880235b62000
Call Trace:
 [<ffffffff8105ea30>] ? default_wake_function+0x0/0x20
 [<ffffffff8118ebe6>] shrink_dcache_for_umount+0x36/0x60
 [<ffffffff81178b2f>] generic_shutdown_super+0x1f/0xe0
 [<ffffffff81178c21>] kill_block_super+0x31/0x50
 [<ffffffff81179be0>] deactivate_super+0x70/0x90
 [<ffffffff81195b8f>] mntput_no_expire+0xbf/0x110
 [<ffffffff8119662b>] sys_umount+0x7b/0x3a0
 [<ffffffff810d4932>] ? audit_syscall_entry+0x272/0x2a0
 [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b
Code:50 30 4c 8b 0a 31 d2 48 85 f6 74 04 48 8b 56 40 48 05 70 02 00 00 48 89 de 48 c7 c7 00 27 7a 81 48 89 04 24 31 c0 e8 ad de 35 00 <0f> 0b eb fe 0f 0b eb fe 55 48 89 e5 53 48 83 ec 08 0f 1f 44 00 
RIP  [<ffffffff8118eba8>] shrink_dcache_for_umount_subtree+0x2a8/0x2b0
 RSP <ffff880237af1de8>