linux-kernel - Re: bcache: unlock new_nodes[i]->write_lock in btree_gc

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Date:   Mon, 20 Apr 2020 14:55:38 +0800
From:   Zhiqiang Liu <liuzhiqiang26@...wei.com>
To:     <colyli@...e.de>, <kmo@...erainc.com>,
        <linux-bcache@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     "wubo (T)" <wubo40@...wei.com>,
        Mingfangsen <mingfangsen@...wei.com>,
        Yanxiaodan <yanxiaodan@...wei.com>,
        linfeilong <linfeilong@...wei.com>
Subject: Re: bcache: unlock new_nodes[i]->write_lock in btree_gc_coalesce

friendly ping...

On 2020/4/15 19:42, Zhiqiang Liu wrote:
> From: Zhiqiang Liu <liuzhiqiang26@...wei.com>
> 
> coccicheck reports:
>   drivers/md//bcache/btree.c:1538:1-7: preceding lock on line 1417
> 
> After obtaining new_nodes[i]->write_lock, we may go to out_nocoalesce
> tag without releasing lock. Here, we add a new tag
> 'out_unlock_nocoalesce' before out_nocoalesce tag to release
> new_nodes[i]->write_lock.
> 
> Fixes: 2a285686c1 ("bcache: btree locking rework")
> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@...wei.com>
> ---
>  drivers/md/bcache/btree.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index fa872df4e770..cad8b0b97e33 100644
> --- a/drivers/md/bcache/btree.c
> +++ b/drivers/md/bcache/btree.c
> @@ -1447,7 +1447,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
>  			if (__set_blocks(n1, n1->keys + n2->keys,
>  					 block_bytes(b->c)) >
>  			    btree_blocks(new_nodes[i]))
> -				goto out_nocoalesce;
> +				goto out_unlock_nocoalesce;
> 
>  			keys = n2->keys;
>  			/* Take the key of the node we're getting rid of */
> @@ -1476,7 +1476,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
> 
>  		if (__bch_keylist_realloc(&keylist,
>  					  bkey_u64s(&new_nodes[i]->key)))
> -			goto out_nocoalesce;
> +			goto out_unlock_nocoalesce;
> 
>  		bch_btree_node_write(new_nodes[i], &cl);
>  		bch_keylist_add(&keylist, &new_nodes[i]->key);
> @@ -1522,6 +1522,10 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
>  	/* Invalidated our iterator */
>  	return -EINTR;
> 
> +out_unlock_nocoalesce:
> +	for (i = 0; i < nodes; i++)
> +		mutex_unlock(&new_nodes[i]->write_lock);
> +
>  out_nocoalesce:
>  	closure_sync(&cl);
>