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Subject: Re: [PATCH] jffs2: Fix use of uninitialized delayed_work, lockdep
 breakage
To:     Hou Tao <houtao1@huawei.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        David Woodhouse <dwmw2@infradead.org>,
        linux-mtd@lists.infradead.org
References: <20181019083020.14335-1-daniel.santos@pobox.com>
 <d2f16a3a-7237-6c4e-5ff8-43f05bdb7e0f@huawei.com>
From:   Daniel Santos <daniel.santos@pobox.com>
Message-ID: <1868afe1-734f-7b44-535a-ac722b6722a4@pobox.com>
Date:   Sun, 21 Oct 2018 23:56:45 -0500
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On 10/21/2018 07:32 PM, Hou Tao wrote:
>
> On 2018/10/19 16:30, Daniel Santos wrote:
>> jffs2_sync_fs makes the assumption that if CONFIG_JFFS2_FS_WRITEBUFFER
>> is defined then a write buffer is available and has been initialized.
>> However, this does is not the case when the mtd device has no
>> out-of-band buffer:
>>
>> int jffs2_nand_flash_setup(struct jffs2_sb_info *c)
>> {
>>         if (!c->mtd->oobsize)
>>                 return 0;
>> ...
>>
>> The resulting call to cancel_delayed_work_sync passing a uninitialized
>> (but zeroed) delayed_work struct forces lockdep to become disabled.
>>
>> [   90.050639] overlayfs: upper fs does not support tmpfile.
>> [   90.652264] INFO: trying to register non-static key.
>> [   90.662171] the code is fine but needs lockdep annotation.
>> [   90.673090] turning off the locking correctness validator.
>> [   90.684021] CPU: 0 PID: 1762 Comm: mount_root Not tainted 4.14.63 #=
0
>> [   90.696672] Stack : 00000000 00000000 80d8f6a2 00000038 805f0000 80=
444600 8fe364f4 805dfbe7
>> [   90.713349]         80563a30 000006e2 8068370c 00000001 00000000 00=
000001 8e2fdc48 ffffffff
>> [   90.730020]         00000000 00000000 80d90000 00000000 00000106 00=
000000 6465746e 312e3420
>> [   90.746690]         6b636f6c 03bf0000 f8000000 20676e69 00000000 80=
000000 00000000 8e2c2a90
>> [   90.763362]         80d90000 00000001 00000000 8e2c2a90 00000003 80=
260dc0 08052098 80680000
>> [   90.780033]         ...
>> [   90.784902] Call Trace:
>> [   90.789793] [<8000f0d8>] show_stack+0xb8/0x148
>> [   90.798659] [<8005a000>] register_lock_class+0x270/0x55c
>> [   90.809247] [<8005cb64>] __lock_acquire+0x13c/0xf7c
>> [   90.818964] [<8005e314>] lock_acquire+0x194/0x1dc
>> [   90.828345] [<8003f27c>] flush_work+0x200/0x24c
>> [   90.837374] [<80041dfc>] __cancel_work_timer+0x158/0x210
>> [   90.847958] [<801a8770>] jffs2_sync_fs+0x20/0x54
>> [   90.857173] [<80125cf4>] iterate_supers+0xf4/0x120
>> [   90.866729] [<80158fc4>] sys_sync+0x44/0x9c
>> [   90.875067] [<80014424>] syscall_common+0x34/0x58
>>
>> Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
>> ---
>>  fs/jffs2/super.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
>> index 793ad30970ff..cae4ecda3c50 100644
>> --- a/fs/jffs2/super.c
>> +++ b/fs/jffs2/super.c
>> @@ -101,7 +101,8 @@ static int jffs2_sync_fs(struct super_block *sb, i=
nt wait)
>>  	struct jffs2_sb_info *c =3D JFFS2_SB_INFO(sb);
>> =20
>>  #ifdef CONFIG_JFFS2_FS_WRITEBUFFER
>> -	cancel_delayed_work_sync(&c->wbuf_dwork);
>> +	if (jffs2_is_writebuffered(c))
>> +		cancel_delayed_work_sync(&c->wbuf_dwork);
>>  #endif
>> =20
>>  	mutex_lock(&c->alloc_sem);
>>
> Reviewed-by: Hou Tao <houtao1@huawei.com>
>
> And I am curious that why is there NAND Flash without OOB area ? So for=
 them
> the ECC data must be saved in data area ?
>
> Regards,
>
> Tao

Thank you.

I'm not intimately familiar with these, but it's an SPI NOR chip and I'm
pretty sure they that they don't have ECC.=C2=A0 Specifically a Winbond
w25q128fv using drivers/mtd/devices/m25p80.c.

Thanks,
Daniel