Re: [Ocfs2-devel] [PATCH] ocfs2: fix crash caused by stale lvb with fsdlm plugin

[Eric Ren]

Hi Gang,

On 12/12/2016 10:56 AM, Gang He wrote:
> Hi Eric,
>
> Looks good for me.
> Just one suggestion,
> please monitor if the LVB sharing mechanism in the cluster still works well 
> in the normal scenario,
> to avoid any performance decrease regression problem.
Thanks for your review. I have done the testing as you suggested, and it works
as expected.

Thanks,
Eric
>
> Reviewed-by: Gang He 
>
> Thanks
> Gang
>
>
>> The crash happens rather often when we reset some cluster
>> nodes while nodes contend fiercely to do truncate and append.
>>
>> The crash backtrace is below:
>> "
>> [  245.197849] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover_grant 1
>> locks on 971 resources
>> [  245.197859] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover 9
>> generation 5 done: 4 ms
>> [  245.198379] ocfs2: Begin replay journal (node 318952601, slot 2) on
>> device (253,18)
>> [  247.272338] ocfs2: End replay journal (node 318952601, slot 2) on device
>> (253,18)
>> [  247.547084] ocfs2: Beginning quota recovery on device (253,18) for slot 2
>> [  247.683263] ocfs2: Finishing quota recovery on device (253,18) for slot 2
>> [  247.833022] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: bug
>> expression: le64_to_cpu(fe->i_size) != i_size_read(inode)
>> [  247.833029] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: Inode
>> 290321, inode i_size = 732 != di i_size = 937, i_flags = 0x1
>> [  247.833074] [ cut here ]
>> [  247.833077] kernel BUG at /usr/src/linux/fs/ocfs2/file.c:470!
>> [  247.833079] invalid opcode:  [#1] SMP
>> [  247.833081] Modules linked in: ocfs2_stack_user(OEN) ocfs2(OEN)
>> ocfs2_nodemanager ocfs2_stackglue(OEN) quota_tree dlm(OEN) configfs fuse
>> sd_modiscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi af_packet
>> iscsi_ibft iscsi_boot_sysfs softdog xfs libcrc32c ppdev parport_pc pcspkr
>> parport  joydev virtio_balloon virtio_net i2c_piix4 acpi_cpufreq button
>> processor ext4 crc16 jbd2 mbcache ata_generic cirrus virtio_blk ata_piix
>>   drm_kms_helper ahci syscopyarea libahci sysfillrect sysimgblt
>> fb_sys_fops ttm floppy libata drm virtio_pci virtio_ring uhci_hcd virtio
>> ehci_hcd   usbcore serio_raw usb_common sg dm_multipath dm_mod
>> scsi_dh_rdac scsi_dh_emc scsi_dh_alua scsi_mod autofs4
>> [  247.833107] Supported: No, Unsupported modules are loaded
>> [  247.833110] CPU: 1 PID: 30154 Comm: truncate Tainted: G   OE   N
>> 4.4.21-69-default #1
>> [  247.833111] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>> rel-1.8.1-0-g4adadbd-20151112_172657-sheep25 04/01/2014
>> [  247.833112] task: 88004ff6d240 ti: 880074e68000 task.ti:
>> 880074e68000
>> [  247.833113] RIP: 0010:[]  []
>> ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
>> [  247.833151] RSP: 0018:880074e6bd50  EFLAGS: 00010282
>> [  247.833152] RAX: 0074 RBX: 029e RCX:
>> 
>> [  247.833153] RDX: 0001 RSI: 0246 RDI:
>> 0246
>> [  247.833154] RBP: 880074e6bda8 R08: 3675dc7a R09:
>> 82013414
>> [  247.833155] R10: 00034c50 R11:  R12:
>> 88003aab3448
>> [  247.833156] R13: 02dc R14: 00046e11 R15:
>> 0020
>> [  247.833157] FS:  7f839f965700() GS:88007fc8()
>> knlGS:
>> [  247.833158] CS:  0010 DS:  ES:  CR0: 8005003b
>> [  247.833159] CR2: 7f839f97e000 CR3: 36723000 CR4:
>> 06e0
>> [  247.833164] Stack:
>> [  247.833165]  03a9 0001 880060554000
>> 88004fcaf000
>> [  247.833167]  88003aa7b090 1000 88003aab3448
>> 880074e6beb0
>> [  247.833169]  0001 2068 0020
>> 
>> [  247.833171] Call Trace:
>> [  247.833208]  [] ocfs2_setattr+0x698/0xa90 [ocfs2]
>> [  247.833225]  [] notify_change+0x1ae/0x380
>> [  247.833242]  [] do_truncate+0x5e/0x90
>> [  247.833246]  [] 
>> do_sys_ftruncate.constprop.11+0x108/0x160
>> [  247.833257]  [] entry_SYSCALL_64_fastpath+0x12/0x6d
>> [  247.834724] DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x12/0x6d
>> [  247.834725]
>> [  247.834726] Leftover inexact backtrace:
>>
>> [  247.834728] Code: 24 28 ba d6 01 00 00 48 c7 c6 30 43 62 a0 8b 41 2c 89
>> 44 24 08 48 8b 41 20 48 c7 c1 78 a3 62 a0 48 89 04 24 31 c0 e8 a0 97 f9 ff 
>> <0f>
>> 0b 3d 00 fe ff ff 0f 84 ab fd ff ff 83 f8 fc 0f 84 a2 fd ff
>> [  247.834748] RIP  [] ocfs2_truncate_file+0x640/0x6c0
>> [ocfs2]
>> [  247.834774]  RSP 
>> "
>>
>> It's because ocfs2_inode_lock() get us stale LVB in which the i_size is not
>> equal to the disk i_size. We mistakenly trust the LVB because the
>> underlaying
>> fsdlm dlm_lock() doesn't set lkb_sbflags with DLM_SBF_VALNOTVALID properly
>> for
>> us. But, why?
>>
>> The current code tries to downconvert lock without DLM_LKF_VALBLK
>> flag to tell o2cb don't update RSB's 

Re: [Ocfs2-devel] [PATCH] ocfs2: fix crash caused by stale lvb with fsdlm plugin

[Gang He]

Hi Eric,

Looks good for me.
Just one suggestion, 
please monitor if the LVB sharing mechanism in the cluster still works well in 
the normal scenario, 
to avoid any performance decrease regression problem.

Reviewed-by: Gang He 

Thanks
Gang


>>> 
> The crash happens rather often when we reset some cluster
> nodes while nodes contend fiercely to do truncate and append.
> 
> The crash backtrace is below:
> "
> [  245.197849] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover_grant 1 
> locks on 971 resources
> [  245.197859] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover 9 
> generation 5 done: 4 ms
> [  245.198379] ocfs2: Begin replay journal (node 318952601, slot 2) on 
> device (253,18)
> [  247.272338] ocfs2: End replay journal (node 318952601, slot 2) on device 
> (253,18)
> [  247.547084] ocfs2: Beginning quota recovery on device (253,18) for slot 2
> [  247.683263] ocfs2: Finishing quota recovery on device (253,18) for slot 2
> [  247.833022] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: bug 
> expression: le64_to_cpu(fe->i_size) != i_size_read(inode)
> [  247.833029] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: Inode 
> 290321, inode i_size = 732 != di i_size = 937, i_flags = 0x1
> [  247.833074] [ cut here ]
> [  247.833077] kernel BUG at /usr/src/linux/fs/ocfs2/file.c:470!
> [  247.833079] invalid opcode:  [#1] SMP
> [  247.833081] Modules linked in: ocfs2_stack_user(OEN) ocfs2(OEN) 
> ocfs2_nodemanager ocfs2_stackglue(OEN) quota_tree dlm(OEN) configfs fuse 
> sd_modiscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi af_packet 
> iscsi_ibft iscsi_boot_sysfs softdog xfs libcrc32c ppdev parport_pc pcspkr 
> parport  joydev virtio_balloon virtio_net i2c_piix4 acpi_cpufreq button 
> processor ext4 crc16 jbd2 mbcache ata_generic cirrus virtio_blk ata_piix  
>  drm_kms_helper ahci syscopyarea libahci sysfillrect sysimgblt 
> fb_sys_fops ttm floppy libata drm virtio_pci virtio_ring uhci_hcd virtio 
> ehci_hcd   usbcore serio_raw usb_common sg dm_multipath dm_mod 
> scsi_dh_rdac scsi_dh_emc scsi_dh_alua scsi_mod autofs4
> [  247.833107] Supported: No, Unsupported modules are loaded
> [  247.833110] CPU: 1 PID: 30154 Comm: truncate Tainted: G   OE   N  
> 4.4.21-69-default #1
> [  247.833111] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 
> rel-1.8.1-0-g4adadbd-20151112_172657-sheep25 04/01/2014
> [  247.833112] task: 88004ff6d240 ti: 880074e68000 task.ti: 
> 880074e68000
> [  247.833113] RIP: 0010:[]  [] 
> ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
> [  247.833151] RSP: 0018:880074e6bd50  EFLAGS: 00010282
> [  247.833152] RAX: 0074 RBX: 029e RCX: 
> 
> [  247.833153] RDX: 0001 RSI: 0246 RDI: 
> 0246
> [  247.833154] RBP: 880074e6bda8 R08: 3675dc7a R09: 
> 82013414
> [  247.833155] R10: 00034c50 R11:  R12: 
> 88003aab3448
> [  247.833156] R13: 02dc R14: 00046e11 R15: 
> 0020
> [  247.833157] FS:  7f839f965700() GS:88007fc8() 
> knlGS:
> [  247.833158] CS:  0010 DS:  ES:  CR0: 8005003b
> [  247.833159] CR2: 7f839f97e000 CR3: 36723000 CR4: 
> 06e0
> [  247.833164] Stack:
> [  247.833165]  03a9 0001 880060554000 
> 88004fcaf000
> [  247.833167]  88003aa7b090 1000 88003aab3448 
> 880074e6beb0
> [  247.833169]  0001 2068 0020 
> 
> [  247.833171] Call Trace:
> [  247.833208]  [] ocfs2_setattr+0x698/0xa90 [ocfs2]
> [  247.833225]  [] notify_change+0x1ae/0x380
> [  247.833242]  [] do_truncate+0x5e/0x90
> [  247.833246]  [] do_sys_ftruncate.constprop.11+0x108/0x160
> [  247.833257]  [] entry_SYSCALL_64_fastpath+0x12/0x6d
> [  247.834724] DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x12/0x6d
> [  247.834725]
> [  247.834726] Leftover inexact backtrace:
> 
> [  247.834728] Code: 24 28 ba d6 01 00 00 48 c7 c6 30 43 62 a0 8b 41 2c 89 
> 44 24 08 48 8b 41 20 48 c7 c1 78 a3 62 a0 48 89 04 24 31 c0 e8 a0 97 f9 ff 
> <0f> 
> 0b 3d 00 fe ff ff 0f 84 ab fd ff ff 83 f8 fc 0f 84 a2 fd ff
> [  247.834748] RIP  [] ocfs2_truncate_file+0x640/0x6c0 
> [ocfs2]
> [  247.834774]  RSP 
> "
> 
> It's because ocfs2_inode_lock() get us stale LVB in which the i_size is not
> equal to the disk i_size. We mistakenly trust the LVB because the 
> underlaying
> fsdlm dlm_lock() doesn't set lkb_sbflags with DLM_SBF_VALNOTVALID properly 
> for
> us. But, why?
> 
> The current code tries to downconvert lock without DLM_LKF_VALBLK
> flag to tell o2cb don't update RSB's LVB if it's a PR->NULL conversion,
> even if the lock resource type needs LVB. This is not the right way for 
> fsdlm.
> 
> The fsdlm plugin behaves different on DLM_LKF_VALBLK, it depends on
> DLM_LKF_VALBLK to decide if we 

Re: [Ocfs2-devel] [PATCH] ocfs2: fix crash caused by stale lvb with fsdlm plugin

[Eric Ren]

Sorry, this email is not delivered to Mark successfully because of one weird 
character
trailing his email address somehow.

So, resend later...

Thanks,
Eric

On 12/09/2016 05:24 PM, Eric Ren wrote:
> The crash happens rather often when we reset some cluster
> nodes while nodes contend fiercely to do truncate and append.
>
> The crash backtrace is below:
> "
> [  245.197849] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover_grant 1 
> locks on 971 resources
> [  245.197859] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover 9 
> generation 5 done: 4 ms
> [  245.198379] ocfs2: Begin replay journal (node 318952601, slot 2) on device 
> (253,18)
> [  247.272338] ocfs2: End replay journal (node 318952601, slot 2) on device 
> (253,18)
> [  247.547084] ocfs2: Beginning quota recovery on device (253,18) for slot 2
> [  247.683263] ocfs2: Finishing quota recovery on device (253,18) for slot 2
> [  247.833022] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: bug 
> expression: le64_to_cpu(fe->i_size) != i_size_read(inode)
> [  247.833029] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: Inode 
> 290321, inode i_size = 732 != di i_size = 937, i_flags = 0x1
> [  247.833074] [ cut here ]
> [  247.833077] kernel BUG at /usr/src/linux/fs/ocfs2/file.c:470!
> [  247.833079] invalid opcode:  [#1] SMP
> [  247.833081] Modules linked in: ocfs2_stack_user(OEN) ocfs2(OEN) 
> ocfs2_nodemanager ocfs2_stackglue(OEN) quota_tree dlm(OEN) configfs fuse 
> sd_modiscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi af_packet 
> iscsi_ibft iscsi_boot_sysfs softdog xfs libcrc32c ppdev parport_pc pcspkr 
> parport  joydev virtio_balloon virtio_net i2c_piix4 acpi_cpufreq button 
> processor ext4 crc16 jbd2 mbcache ata_generic cirrus virtio_blk ata_piix  
>  drm_kms_helper ahci syscopyarea libahci sysfillrect sysimgblt 
> fb_sys_fops ttm floppy libata drm virtio_pci virtio_ring uhci_hcd virtio 
> ehci_hcd   usbcore serio_raw usb_common sg dm_multipath dm_mod 
> scsi_dh_rdac scsi_dh_emc scsi_dh_alua scsi_mod autofs4
> [  247.833107] Supported: No, Unsupported modules are loaded
> [  247.833110] CPU: 1 PID: 30154 Comm: truncate Tainted: G   OE   N  
> 4.4.21-69-default #1
> [  247.833111] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 
> rel-1.8.1-0-g4adadbd-20151112_172657-sheep25 04/01/2014
> [  247.833112] task: 88004ff6d240 ti: 880074e68000 task.ti: 
> 880074e68000
> [  247.833113] RIP: 0010:[]  [] 
> ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
> [  247.833151] RSP: 0018:880074e6bd50  EFLAGS: 00010282
> [  247.833152] RAX: 0074 RBX: 029e RCX: 
> 
> [  247.833153] RDX: 0001 RSI: 0246 RDI: 
> 0246
> [  247.833154] RBP: 880074e6bda8 R08: 3675dc7a R09: 
> 82013414
> [  247.833155] R10: 00034c50 R11:  R12: 
> 88003aab3448
> [  247.833156] R13: 02dc R14: 00046e11 R15: 
> 0020
> [  247.833157] FS:  7f839f965700() GS:88007fc8() 
> knlGS:
> [  247.833158] CS:  0010 DS:  ES:  CR0: 8005003b
> [  247.833159] CR2: 7f839f97e000 CR3: 36723000 CR4: 
> 06e0
> [  247.833164] Stack:
> [  247.833165]  03a9 0001 880060554000 
> 88004fcaf000
> [  247.833167]  88003aa7b090 1000 88003aab3448 
> 880074e6beb0
> [  247.833169]  0001 2068 0020 
> 
> [  247.833171] Call Trace:
> [  247.833208]  [] ocfs2_setattr+0x698/0xa90 [ocfs2]
> [  247.833225]  [] notify_change+0x1ae/0x380
> [  247.833242]  [] do_truncate+0x5e/0x90
> [  247.833246]  [] do_sys_ftruncate.constprop.11+0x108/0x160
> [  247.833257]  [] entry_SYSCALL_64_fastpath+0x12/0x6d
> [  247.834724] DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x12/0x6d
> [  247.834725]
> [  247.834726] Leftover inexact backtrace:
>
> [  247.834728] Code: 24 28 ba d6 01 00 00 48 c7 c6 30 43 62 a0 8b 41 2c 89 44 
> 24 08 48 8b 41 20 48 c7 c1 78 a3 62 a0 48 89 04 24 31 c0 e8 a0 97 f9 ff <0f> 
> 0b 3d 00 fe ff ff 0f 84 ab fd ff ff 83 f8 fc 0f 84 a2 fd ff
> [  247.834748] RIP  [] ocfs2_truncate_file+0x640/0x6c0 
> [ocfs2]
> [  247.834774]  RSP 
> "
>
> It's because ocfs2_inode_lock() get us stale LVB in which the i_size is not
> equal to the disk i_size. We mistakenly trust the LVB because the underlaying
> fsdlm dlm_lock() doesn't set lkb_sbflags with DLM_SBF_VALNOTVALID properly for
> us. But, why?
>
> The current code tries to downconvert lock without DLM_LKF_VALBLK
> flag to tell o2cb don't update RSB's LVB if it's a PR->NULL conversion,
> even if the lock resource type needs LVB. This is not the right way for fsdlm.
>
> The fsdlm plugin behaves different on DLM_LKF_VALBLK, it depends on
> DLM_LKF_VALBLK to decide if we care about the LVB in the LKB. If 
> DLM_LKF_VALBLK
> is not set, fsdlm will skip 

[Ocfs2-devel] [PATCH] ocfs2: fix crash caused by stale lvb with fsdlm plugin

[Eric Ren]

The crash happens rather often when we reset some cluster
nodes while nodes contend fiercely to do truncate and append.

The crash backtrace is below:
"
[  245.197849] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover_grant 1 locks 
on 971 resources
[  245.197859] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover 9 generation 
5 done: 4 ms
[  245.198379] ocfs2: Begin replay journal (node 318952601, slot 2) on device 
(253,18)
[  247.272338] ocfs2: End replay journal (node 318952601, slot 2) on device 
(253,18)
[  247.547084] ocfs2: Beginning quota recovery on device (253,18) for slot 2
[  247.683263] ocfs2: Finishing quota recovery on device (253,18) for slot 2
[  247.833022] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: bug 
expression: le64_to_cpu(fe->i_size) != i_size_read(inode)
[  247.833029] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: Inode 290321, 
inode i_size = 732 != di i_size = 937, i_flags = 0x1
[  247.833074] [ cut here ]
[  247.833077] kernel BUG at /usr/src/linux/fs/ocfs2/file.c:470!
[  247.833079] invalid opcode:  [#1] SMP
[  247.833081] Modules linked in: ocfs2_stack_user(OEN) ocfs2(OEN) 
ocfs2_nodemanager ocfs2_stackglue(OEN) quota_tree dlm(OEN) configfs fuse sd_mod 
   iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi af_packet iscsi_ibft 
iscsi_boot_sysfs softdog xfs libcrc32c ppdev parport_pc pcspkr parport  
joydev virtio_balloon virtio_net i2c_piix4 acpi_cpufreq button processor ext4 
crc16 jbd2 mbcache ata_generic cirrus virtio_blk ata_piix   
drm_kms_helper ahci syscopyarea libahci sysfillrect sysimgblt fb_sys_fops ttm 
floppy libata drm virtio_pci virtio_ring uhci_hcd virtio ehci_hcd   usbcore 
serio_raw usb_common sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc 
scsi_dh_alua scsi_mod autofs4
[  247.833107] Supported: No, Unsupported modules are loaded
[  247.833110] CPU: 1 PID: 30154 Comm: truncate Tainted: G   OE   N  
4.4.21-69-default #1
[  247.833111] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 
rel-1.8.1-0-g4adadbd-20151112_172657-sheep25 04/01/2014
[  247.833112] task: 88004ff6d240 ti: 880074e68000 task.ti: 
880074e68000
[  247.833113] RIP: 0010:[]  [] 
ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
[  247.833151] RSP: 0018:880074e6bd50  EFLAGS: 00010282
[  247.833152] RAX: 0074 RBX: 029e RCX: 
[  247.833153] RDX: 0001 RSI: 0246 RDI: 0246
[  247.833154] RBP: 880074e6bda8 R08: 3675dc7a R09: 82013414
[  247.833155] R10: 00034c50 R11:  R12: 88003aab3448
[  247.833156] R13: 02dc R14: 00046e11 R15: 0020
[  247.833157] FS:  7f839f965700() GS:88007fc8() 
knlGS:
[  247.833158] CS:  0010 DS:  ES:  CR0: 8005003b
[  247.833159] CR2: 7f839f97e000 CR3: 36723000 CR4: 06e0
[  247.833164] Stack:
[  247.833165]  03a9 0001 880060554000 
88004fcaf000
[  247.833167]  88003aa7b090 1000 88003aab3448 
880074e6beb0
[  247.833169]  0001 2068 0020 

[  247.833171] Call Trace:
[  247.833208]  [] ocfs2_setattr+0x698/0xa90 [ocfs2]
[  247.833225]  [] notify_change+0x1ae/0x380
[  247.833242]  [] do_truncate+0x5e/0x90
[  247.833246]  [] do_sys_ftruncate.constprop.11+0x108/0x160
[  247.833257]  [] entry_SYSCALL_64_fastpath+0x12/0x6d
[  247.834724] DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x12/0x6d
[  247.834725]
[  247.834726] Leftover inexact backtrace:

[  247.834728] Code: 24 28 ba d6 01 00 00 48 c7 c6 30 43 62 a0 8b 41 2c 89 44 
24 08 48 8b 41 20 48 c7 c1 78 a3 62 a0 48 89 04 24 31 c0 e8 a0 97 f9 ff <0f> 0b 
3d 00 fe ff ff 0f 84 ab fd ff ff 83 f8 fc 0f 84 a2 fd ff
[  247.834748] RIP  [] ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
[  247.834774]  RSP 
"

It's because ocfs2_inode_lock() get us stale LVB in which the i_size is not
equal to the disk i_size. We mistakenly trust the LVB because the underlaying
fsdlm dlm_lock() doesn't set lkb_sbflags with DLM_SBF_VALNOTVALID properly for
us. But, why?

The current code tries to downconvert lock without DLM_LKF_VALBLK
flag to tell o2cb don't update RSB's LVB if it's a PR->NULL conversion,
even if the lock resource type needs LVB. This is not the right way for fsdlm.

The fsdlm plugin behaves different on DLM_LKF_VALBLK, it depends on
DLM_LKF_VALBLK to decide if we care about the LVB in the LKB. If DLM_LKF_VALBLK
is not set, fsdlm will skip recovering RSB's LVB from this lkb and set the right
DLM_SBF_VALNOTVALID appropriately when node failure happens.

The following diagram briefly illustrates how this crash happens:

RSB1 is inode metadata lock resource with LOCK_TYPE_USES_LVB;

The 1st round:

 Node1Node2
RSB1: PR