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Subject: Re: [f2fs-dev] Writes stoped working on f2fs after the compression
 support was added
To:     Jaegeuk Kim <jaegeuk@kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>
References: <20191209222345.1078-1-jaegeuk@kernel.org>
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 <20200224140349.74yagjdwewmclx4v@core.my.home>
 <20200224143149.au6hvmmfw4ajsq2g@core.my.home>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <39712bf4-210b-d7b6-cbb1-eb57585d991a@huawei.com>
Date:   Tue, 25 Feb 2020 19:24:12 +0800
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On 2020/2/24 22:31, Ondřej Jirman wrote:
> On Mon, Feb 24, 2020 at 03:03:49PM +0100, megi xff wrote:
>> On Mon, Feb 24, 2020 at 02:58:37PM +0100, megi xff wrote:
>>> Hello,
>>>
>>> On Mon, Feb 24, 2020 at 06:41:03PM +0800, Chao Yu wrote:
>>>> On 2020/2/24 18:37, Chao Yu wrote:
>>>>> Hi,
>>>>>
>>>>> Thanks for the report.
>>>>>
>>>>> Could you dump all other task stack info via "echo "t" > /proc/sysrq-trigger"?
>>>>>
>>>>>>
>>>>>> [  246.758021] INFO: task kworker/u16:1:58 blocked for more than 122 seconds.
>>>>>> [  246.758040]       Not tainted 5.6.0-rc2-00590-g9983bdae4974e #11
>>>>>> [  246.758044] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>>>>>> [  246.758052] kworker/u16:1   D    0    58      2 0x00000000
>>>>>> [  246.758090] Workqueue: writeback wb_workfn (flush-179:0)
>>>>>> [  246.758099] Backtrace:
>>>>>> [  246.758121] [<c0912b90>] (__schedule) from [<c0913234>] (schedule+0x78/0xf4)
>>>>>> [  246.758130]  r10:da644000 r9:00000000 r8:da645a60 r7:da283e10 r6:00000002 r5:da644000
>>>>>> [  246.758132]  r4:da4d3600
>>>>>> [  246.758148] [<c09131bc>] (schedule) from [<c017ec74>] (rwsem_down_write_slowpath+0x24c/0x4c0)
>>>>>> [  246.758152]  r5:00000001 r4:da283e00
>>>>>> [  246.758161] [<c017ea28>] (rwsem_down_write_slowpath) from [<c0915f2c>] (down_write+0x6c/0x70)
>>>>>> [  246.758167]  r10:da283e00 r9:da645d80 r8:d9ed0000 r7:00000001 r6:00000000 r5:eff213b0
>>>>>> [  246.758169]  r4:da283e00
>>>>>> [  246.758187] [<c0915ec0>] (down_write) from [<c0435b80>] (f2fs_write_single_data_page+0x608/0x7ac)
>>>>>
>>>>> I'm not sure what is this semaphore, I suspect this is F2FS_I(inode)->i_sem, in order to make
>>>>> sure of this, can you help to add below function, and use them to replace
>>>>> all {down,up}_{write,read}(&.i_sem) invoking? then reproduce this issue and catch the log.
>>>>
>>>> Sorry, just forgot attaching below function.
>>>>
>>>> void inode_down_write(struct inode *inode)
>>>> {
>>>> 	printk("%s from %pS\n", __func__, __builtin_return_address(0));
>>>> 	down_write(&F2FS_I(inode)->i_sem);
>>>> }
>>>>
>>>> void inode_up_write(struct inode *inode)
>>>> {
>>>> 	up_write(&F2FS_I(inode)->i_sem);
>>>> 	printk("%s from %pS\n", __func__, __builtin_return_address(0));
>>>> }
>>>>
>>>> void inode_down_read(struct inode *inode)
>>>> {
>>>> 	printk("%s from %pS\n", __func__, __builtin_return_address(0));
>>>> 	down_read(&F2FS_I(inode)->i_sem);
>>>> }
>>>>
>>>> void inode_up_read(struct inode *inode)
>>>> {
>>>> 	up_read(&F2FS_I(inode)->i_sem);
>>>> 	printk("%s from %pS\n", __func__, __builtin_return_address(0));
>>>> }
>>>>
>>>
>>> Here's the log and vmlinux file that may help mapping the code addresses back to
>>> code, hope it helps:
>>>
>>> https://megous.com/dl/tmp/f2fs-dmesg-log
>>> https://megous.com/dl/tmp/f2fs-log-build-artifacts.tar.gz
>>
>> Just by a looks of it:
>>
>> root@tbs2[/proc/sys/kernel] # dmesg | grep up_write | wc -l
>> 324
>> root@tbs2[/proc/sys/kernel] # dmesg | grep down_write | wc -l
>> 347
>>
>> there seems to be a mismatch of lock/unlock counts.
>  
> Sorry, a wrong grep expression.
> 
> root@tbs2[~] # dmesg | grep inode_down_write | wc -l
> 357
> root@tbs2[~] # dmesg | grep inode_up_write | wc -l
> 357
> root@tbs2[~] # dmesg | grep inode_up_read | wc -l
> 16
> root@tbs2[~] # dmesg | grep inode_down_read | wc -l
> 16

I don't know why we have consistent down/up pair, but through disassembled
code, I doubt it's the f2fs_inode->i_sem.

c0435d7c:       ebf54af8        bl      c0188964 <printk>
c0435d80:       e1a00006        mov     r0, r6
c0435d84:       eb138135        bl      c0916260 <down_write>

inode_down_write()

c0435d88:       e284ce1d        add     ip, r4, #464    ; 0x1d0

We are stuck here.

[  430.675754] [<c0916260>] (down_write) from [<c0435d88>] (f2fs_write_single_data_page+0x600/0x7d8)
                                                ^^^^^^^^^
[  430.675764] [<c0435788>] (f2fs_write_single_data_page) from [<c0436214>] (f2fs_write_cache_pages+0x2b4/0x7c4)


c0435d8c:       e14b0ad4        ldrd    r0, [fp, #-164] ; 0xffffff5c
c0435d90:       e1cc20d0        ldrd    r2, [ip]
c0435d94:       e1520000        cmp     r2, r0
c0435d98:       e0d33001        sbcs    r3, r3, r1
c0435d9c:       b1cc00f0        strdlt  r0, [ip]
c0435da0:       e1a00006        mov     r0, r6
c0435da4:       ebf52227        bl      c017e648 <up_write>
c0435da8:       e51b2098        ldr     r2, [fp, #-152] ; 0xffffff68
c0435dac:       e30c0730        movw    r0, #50992      ; 0xc730
c0435db0:       e59f11a4        ldr     r1, [pc, #420]  ; c0435f5c <f2fs_write_single_data_page+0x7d4>
c0435db4:       e34c00b6        movt    r0, #49334      ; 0xc0b6
c0435db8:       ebf54ae9        bl      c0188964 <printk>

inode_up_write()

Thanks,

> 
> So it's probably not inode locking.
> 
>> root@tbs2[/proc/sys/kernel] # dmesg | grep down_read | wc -l
>> 16
>> root@tbs2[/proc/sys/kernel] # dmesg | grep up_read | wc -l
>> 16
>>
>> regards,
>> 	o.
>>
>>> thank you,
>>> 	o.
>>>
>>>>> Thanks,
>>>>>
>>>>>> [  246.758190]  r5:eff213b0 r4:da283c60
>>>>>> [  246.758198] [<c0435578>] (f2fs_write_single_data_page) from [<c0435fd8>] (f2fs_write_cache_pages+0x2b4/0x7c4)
>>>>>> [  246.758204]  r10:da645c28 r9:da283d60 r8:da283c60 r7:0000000f r6:da645d80 r5:00000001
>>>>>> [  246.758206]  r4:eff213b0
>>>>>> [  246.758214] [<c0435d24>] (f2fs_write_cache_pages) from [<c043682c>] (f2fs_write_data_pages+0x344/0x35c)
>>>>>> [  246.758220]  r10:00000000 r9:d9ed002c r8:d9ed0000 r7:00000004 r6:da283d60 r5:da283c60
>>>>>> [  246.758223]  r4:da645d80
>>>>>> [  246.758238] [<c04364e8>] (f2fs_write_data_pages) from [<c0267ee8>] (do_writepages+0x3c/0xd4)
>>>>>> [  246.758244]  r10:0000000a r9:c0e03d00 r8:00000c00 r7:c0264ddc r6:da645d80 r5:da283d60
>>>>>> [  246.758246]  r4:da283c60
>>>>>> [  246.758254] [<c0267eac>] (do_writepages) from [<c0310cbc>] (__writeback_single_inode+0x44/0x454)
>>>>>> [  246.758259]  r7:da283d60 r6:da645eac r5:da645d80 r4:da283c60
>>>>>> [  246.758266] [<c0310c78>] (__writeback_single_inode) from [<c03112d0>] (writeback_sb_inodes+0x204/0x4b0)
>>>>>> [  246.758272]  r10:0000000a r9:c0e03d00 r8:da283cc8 r7:da283c60 r6:da645eac r5:da283d08
>>>>>> [  246.758274]  r4:d9dc9848
>>>>>> [  246.758281] [<c03110cc>] (writeback_sb_inodes) from [<c03115cc>] (__writeback_inodes_wb+0x50/0xe4)
>>>>>> [  246.758287]  r10:da3797a8 r9:c0e03d00 r8:d9dc985c r7:da645eac r6:00000000 r5:d9dc9848
>>>>>> [  246.758289]  r4:da5a8800
>>>>>> [  246.758296] [<c031157c>] (__writeback_inodes_wb) from [<c03118f4>] (wb_writeback+0x294/0x338)
>>>>>> [  246.758302]  r10:fffbf200 r9:da644000 r8:c0e04e64 r7:d9dc9848 r6:d9dc9874 r5:da645eac
>>>>>> [  246.758305]  r4:d9dc9848
>>>>>> [  246.758312] [<c0311660>] (wb_writeback) from [<c0312dac>] (wb_workfn+0x35c/0x54c)
>>>>>> [  246.758318]  r10:da5f2005 r9:d9dc984c r8:d9dc9948 r7:d9dc9848 r6:00000000 r5:d9dc9954
>>>>>> [  246.758321]  r4:000031e6
>>>>>> [  246.758334] [<c0312a50>] (wb_workfn) from [<c014f2b8>] (process_one_work+0x214/0x544)
>>>>>> [  246.758340]  r10:da5f2005 r9:00000200 r8:00000000 r7:da5f2000 r6:ef044400 r5:da5eb000
>>>>>> [  246.758343]  r4:d9dc9954
>>>>>> [  246.758350] [<c014f0a4>] (process_one_work) from [<c014f634>] (worker_thread+0x4c/0x574)
>>>>>> [  246.758357]  r10:ef044400 r9:c0e03d00 r8:ef044418 r7:00000088 r6:ef044400 r5:da5eb014
>>>>>> [  246.758359]  r4:da5eb000
>>>>>> [  246.758368] [<c014f5e8>] (worker_thread) from [<c01564fc>] (kthread+0x144/0x170)
>>>>>> [  246.758374]  r10:ec9e5e90 r9:dabf325c r8:da5eb000 r7:da644000 r6:00000000 r5:da5fe000
>>>>>> [  246.758377]  r4:dabf3240
>>>>>> [  246.758386] [<c01563b8>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
>>>>>> [  246.758391] Exception stack(0xda645fb0 to 0xda645ff8)
>>>>>> [  246.758397] 5fa0:                                     00000000 00000000 00000000 00000000
>>>>>> [  246.758402] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>>>>> [  246.758407] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>>>>> [  246.758413]  r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:c01563b8
>>>>>> [  246.758416]  r4:da5fe000
>>>>>> .
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Linux-f2fs-devel mailing list
>>>>> Linux-f2fs-devel@lists.sourceforge.net
>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>>>
> .
>