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Subject: Re: [PATCH v2] lightnvm: pblk-recovery: lightnvm: pblk: Fix two
 sleep-in-atomic-context bugs
To:     javier@cnexlabs.com, baijiaju1990@gmail.com
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20180905084017.27593-1-baijiaju1990@gmail.com>
 <4FEA8984-5E08-44E1-9E5C-03A6516AF7F6@cnexlabs.com>
From:   =?UTF-8?Q?Matias_Bj=c3=b8rling?= <mb@lightnvm.io>
Message-ID: <07fd7366-3deb-6c3e-1cc9-b0dcfdd9ad9f@lightnvm.io>
Date:   Fri, 7 Sep 2018 12:00:55 +0200
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On 09/06/2018 03:18 PM, Javier Gonzalez wrote:
>> On 5 Sep 2018, at 01.40, Jia-Ju Bai <baijiaju1990@gmail.com> wrote:
>>
>> The driver may sleep with holding a spinlock.
>>
>> The function call paths (from bottom to top) in Linux-4.16 are:
>>
>> [FUNC] nvm_dev_dma_alloc(GFP_KERNEL)
>> drivers/lightnvm/pblk-core.c, 754:
>> 	nvm_dev_dma_alloc in pblk_line_submit_smeta_io
>> drivers/lightnvm/pblk-core.c, 1048:
>> 	pblk_line_submit_smeta_io in pblk_line_init_bb
>> drivers/lightnvm/pblk-core.c, 1434:
>> 	pblk_line_init_bb in pblk_line_replace_data
>> drivers/lightnvm/pblk-recovery.c, 980:
>> 	pblk_line_replace_data in pblk_recov_l2p
>> drivers/lightnvm/pblk-recovery.c, 976:
>> 	spin_lock in pblk_recov_l2p
>>
>> [FUNC] bio_map_kern(GFP_KERNEL)
>> drivers/lightnvm/pblk-core.c, 762:
>> 	bio_map_kern in pblk_line_submit_smeta_io
>> drivers/lightnvm/pblk-core.c, 1048:
>> 	pblk_line_submit_smeta_io in pblk_line_init_bb
>> drivers/lightnvm/pblk-core.c, 1434:
>> 	pblk_line_init_bb in pblk_line_replace_data
>> drivers/lightnvm/pblk-recovery.c, 980:
>> 	pblk_line_replace_data in pblk_recov_l2p
>> drivers/lightnvm/pblk-recovery.c, 976:
>> 	spin_lock in pblk_recov_l2p
>>
>> To fix these bugs, the call to pblk_line_replace_data()
>> is moved out of the spinlock protection.
>>
>> These bugs are found by my static analysis tool DSAC.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>> ---
>> v2:
>> * Move the call to pblk_line_replace_data() out of the spinlock
>>   protection, instead of v1 that changes GFP_KERNEL to GFP_ATOMIC in
>>   the calls to bio_map_kern() and nvm_dev_dma_alloc().
>>   Thanks Javier for good advice.
>> ---
>> drivers/lightnvm/pblk-recovery.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
>> index 3a5069183859..5fde414d78bb 100644
>> --- a/drivers/lightnvm/pblk-recovery.c
>> +++ b/drivers/lightnvm/pblk-recovery.c
>> @@ -955,12 +955,14 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
>> 		}
>> 	}
>>
>> -	spin_lock(&l_mg->free_lock);
>> 	if (!open_lines) {
>> +		spin_lock(&l_mg->free_lock);
>> 		WARN_ON_ONCE(!test_and_clear_bit(meta_line,
>> 							&l_mg->meta_bitmap));
>> +		spin_unlock(&l_mg->free_lock);
>> 		pblk_line_replace_data(pblk);
>> 	} else {
>> +		spin_lock(&l_mg->free_lock);
>> 		/* Allocate next line for preparation */
>> 		l_mg->data_next = pblk_line_get(pblk);
>> 		if (l_mg->data_next) {
>> @@ -968,8 +970,8 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
>> 			l_mg->data_next->type = PBLK_LINETYPE_DATA;
>> 			is_next = 1;
>> 		}
>> +		spin_unlock(&l_mg->free_lock);
>> 	}
>> -	spin_unlock(&l_mg->free_lock);
>>
>> 	if (is_next)
>> 		pblk_line_erase(pblk, l_mg->data_next);
>> --
>> 2.17.0
> 
> It looks good to me. Thanks Jia-Ju.
> 
> Reviewed-by: Javier González <javier@cnexlabs.com>
> 

Thanks. Applied for 4.20.