linux-kernel - Re: [PATCH v2] lightnvm: pblk-recovery: lightnvm: pblk: Fix two sleep-in-atomic-context bugs

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Date:   Thu, 6 Sep 2018 13:18:15 +0000
From:   Javier Gonzalez <javier@...xlabs.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
CC:     Matias Bjørling <mb@...htnvm.io>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] lightnvm: pblk-recovery: lightnvm: pblk: Fix two
 sleep-in-atomic-context bugs

> On 5 Sep 2018, at 01.40, Jia-Ju Bai <baijiaju1990@...il.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@...il.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@...xlabs.com>


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