[Ocfs2-devel] [PATCH v2] ocfs2: try a blocking lock before return AOP_TRUNCATED_PAGE
Gang He
ghe at suse.com
Thu Jan 4 22:31:12 PST 2018
Hi Andrew,
Happy new year.
Could you help to pick up this patch, which is used to fix a old patch 1cce4df04f37.
If we have not this patch, some multiple node test cases will trigger softlockup problems,
also make HA communication daemon (e.g. corosync) timeout and the node will has to be fenced.
Thanks
Gang
>>>
>
> On 17/12/28 15:48, Gang He wrote:
>> If we can't get inode lock immediately in the function
>> ocfs2_inode_lock_with_page() when reading a page, we should not
>> return directly here, since this will lead to a softlockup problem
>> when the kernel is configured with CONFIG_PREEMPT is not set.
>> The method is to get a blocking lock and immediately unlock before
>> returning, this can avoid CPU resource waste due to lots of retries,
>> and benefits fairness in getting lock among multiple nodes, increase
>> efficiency in case modifying the same file frequently from multiple
>> nodes.
>> The softlockup crash (when set /proc/sys/kernel/softlockup_panic to 1)
>> looks like,
>> Kernel panic - not syncing: softlockup: hung tasks
>> CPU: 0 PID: 885 Comm: multi_mmap Tainted: G L 4.12.14-6.1-default #1
>> Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
>> Call Trace:
>> <IRQ>
>> dump_stack+0x5c/0x82
>> panic+0xd5/0x21e
>> watchdog_timer_fn+0x208/0x210
>> ? watchdog_park_threads+0x70/0x70
>> __hrtimer_run_queues+0xcc/0x200
>> hrtimer_interrupt+0xa6/0x1f0
>> smp_apic_timer_interrupt+0x34/0x50
>> apic_timer_interrupt+0x96/0xa0
>> </IRQ>
>> RIP: 0010:unlock_page+0x17/0x30
>> RSP: 0000:ffffaf154080bc88 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
>> RAX: dead000000000100 RBX: fffff21e009f5300 RCX: 0000000000000004
>> RDX: dead0000000000ff RSI: 0000000000000202 RDI: fffff21e009f5300
>> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffaf154080bb00
>> R10: ffffaf154080bc30 R11: 0000000000000040 R12: ffff993749a39518
>> R13: 0000000000000000 R14: fffff21e009f5300 R15: fffff21e009f5300
>> ocfs2_inode_lock_with_page+0x25/0x30 [ocfs2]
>> ocfs2_readpage+0x41/0x2d0 [ocfs2]
>> ? pagecache_get_page+0x30/0x200
>> filemap_fault+0x12b/0x5c0
>> ? recalc_sigpending+0x17/0x50
>> ? __set_task_blocked+0x28/0x70
>> ? __set_current_blocked+0x3d/0x60
>> ocfs2_fault+0x29/0xb0 [ocfs2]
>> __do_fault+0x1a/0xa0
>> __handle_mm_fault+0xbe8/0x1090
>> handle_mm_fault+0xaa/0x1f0
>> __do_page_fault+0x235/0x4b0
>> trace_do_page_fault+0x3c/0x110
>> async_page_fault+0x28/0x30
>> RIP: 0033:0x7fa75ded638e
>> RSP: 002b:00007ffd6657db18 EFLAGS: 00010287
>> RAX: 000055c7662fb700 RBX: 0000000000000001 RCX: 000055c7662fb700
>> RDX: 0000000000001770 RSI: 00007fa75e909000 RDI: 000055c7662fb700
>> RBP: 0000000000000003 R08: 000000000000000e R09: 0000000000000000
>> R10: 0000000000000483 R11: 00007fa75ded61b0 R12: 00007fa75e90a770
>> R13: 000000000000000e R14: 0000000000001770 R15: 0000000000000000
>>
>> About performance improvement, we can see the testing time is reduced,
>> and CPU utilization decreases, the detailed data is as follows.
>> I ran multi_mmap test case in ocfs2-test package in a three nodes cluster.
>> Before apply this patch,
>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
>> 2754 ocfs2te+ 20 0 170248 6980 4856 D 80.73 0.341 0:18.71
> multi_mmap
>> 1505 root rt 0 222236 123060 97224 S 2.658 6.015 0:01.44
> corosync
>> 5 root 20 0 0 0 0 S 1.329 0.000 0:00.19
> kworker/u8:0
>> 95 root 20 0 0 0 0 S 1.329 0.000 0:00.25
> kworker/u8:1
>> 2728 root 20 0 0 0 0 S 0.997 0.000 0:00.24
> jbd2/sda1-33
>> 2721 root 20 0 0 0 0 S 0.664 0.000 0:00.07
> ocfs2dc-3C8CFD4
>> 2750 ocfs2te+ 20 0 142976 4652 3532 S 0.664 0.227 0:00.28 mpirun
>>
>> ocfs2test at tb-node2:~>multiple_run.sh -i ens3 -k ~/linux-4.4.21-69.tar.gz -o
>> ~/ocfs2mullog -C hacluster -s pcmk -n tb-node2,tb-node1,tb-node3 -d
>> /dev/sda1 -b 4096 -c 32768 -t multi_mmap /mnt/shared
>> Tests with "-b 4096 -C 32768"
>> Thu Dec 28 14:44:52 CST 2017
>> multi_mmap..................................................Passed.
>> Runtime 783 seconds.
>>
>> After apply this patch,
>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
>> 2508 ocfs2te+ 20 0 170248 6804 4680 R 54.00 0.333 0:55.37
> multi_mmap
>> 155 root 20 0 0 0 0 S 2.667 0.000 0:01.20
> kworker/u8:3
>> 95 root 20 0 0 0 0 S 2.000 0.000 0:01.58
> kworker/u8:1
>> 2504 ocfs2te+ 20 0 142976 4604 3480 R 1.667 0.225 0:01.65 mpirun
>> 5 root 20 0 0 0 0 S 1.000 0.000 0:01.36
> kworker/u8:0
>> 2482 root 20 0 0 0 0 S 1.000 0.000 0:00.86
> jbd2/sda1-33
>> 299 root 0 -20 0 0 0 S 0.333 0.000 0:00.13
> kworker/2:1H
>> 335 root 0 -20 0 0 0 S 0.333 0.000 0:00.17
> kworker/1:1H
>> 535 root 20 0 12140 7268 1456 S 0.333 0.355 0:00.34 haveged
>> 1282 root rt 0 222284 123108 97224 S 0.333 6.017 0:01.33
> corosync
>>
>> ocfs2test at tb-node2:~>multiple_run.sh -i ens3 -k ~/linux-4.4.21-69.tar.gz -o
>> ~/ocfs2mullog -C hacluster -s pcmk -n tb-node2,tb-node1,tb-node3 -d
>> /dev/sda1 -b 4096 -c 32768 -t multi_mmap /mnt/shared
>> Tests with "-b 4096 -C 32768"
>> Thu Dec 28 15:04:12 CST 2017
>> multi_mmap..................................................Passed.
>> Runtime 487 seconds.
>>
>> Fixes: 1cce4df04f37 ("ocfs2: do not lock/unlock() inode DLM lock")
>> Signed-off-by: Gang He <ghe at suse.com>
> Reviewed-by: Joseph Qi <jiangqi903 at gmail.com>
>
>> ---
>> fs/ocfs2/dlmglue.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
>> index 4689940..5193218 100644
>> --- a/fs/ocfs2/dlmglue.c
>> +++ b/fs/ocfs2/dlmglue.c
>> @@ -2486,6 +2486,15 @@ int ocfs2_inode_lock_with_page(struct inode *inode,
>> ret = ocfs2_inode_lock_full(inode, ret_bh, ex, OCFS2_LOCK_NONBLOCK);
>> if (ret == -EAGAIN) {
>> unlock_page(page);
>> + /*
>> + * If we can't get inode lock immediately, we should not return
>> + * directly here, since this will lead to a softlockup problem.
>> + * The method is to get a blocking lock and immediately unlock
>> + * before returning, this can avoid CPU resource waste due to
>> + * lots of retries, and benefits fairness in getting lock.
>> + */
>> + if (ocfs2_inode_lock(inode, ret_bh, ex) == 0)
>> + ocfs2_inode_unlock(inode, ex);
>> ret = AOP_TRUNCATED_PAGE;
>> }
>>
>>
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