linux-kernel - Re: [RESEBD PATCH v3] bcache: Remove some unnecessary NULL point check for the return value of __bch_btree_node

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Date:   Fri, 17 Feb 2023 13:57:28 -0800 (PST)
From:   Eric Wheeler <bcache@...ts.ewheeler.net>
To:     Zheng Wang <zyytlz.wz@....com>
cc:     colyli@...e.de, hackerzheng666@...il.com,
        kent.overstreet@...il.com, linux-bcache@...r.kernel.org,
        linux-kernel@...r.kernel.org, alex000young@...il.com,
        stable@...r.kernel.org
Subject: Re: [RESEBD PATCH v3] bcache: Remove some unnecessary NULL point
 check for the return value of __bch_btree_node_alloc-related pointer

On Fri, 17 Feb 2023, Zheng Wang wrote:

> Due to the previously fix of __bch_btree_node_alloc, the return value will
> never be a NULL pointer. So IS_ERR is enough to handle the failure
>  situation. Fix it by replacing IS_ERR_OR_NULL check to IS_ERR check.
> 
> Fixes: cafe56359144 ("bcache: A block layer cache")
> Cc: stable@...r.kernel.org
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---
> v3:
> - Add Cc: stable@...r.kernel.org suggested by Eric

Make sure that the commit
	bcache: Fix __bch_btree_node_alloc to make the failure behavior consistent
is committed _before_ this "Remove some unnecessary NULL point check..." 
patch.

It would be a good idea to add "this patch depends on `bcache: Fix 
__bch_btree_node_alloc to make the failure behavior consistent`" to the 
commit message so the stable maintainers know.

-Eric

> v2:
> - Replace more checks
> ---
>  drivers/md/bcache/btree.c | 10 +++++-----
>  drivers/md/bcache/super.c |  4 ++--
>  2 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index 147c493a989a..7c21e54468bf 100644
> --- a/drivers/md/bcache/btree.c
> +++ b/drivers/md/bcache/btree.c
> @@ -1138,7 +1138,7 @@ static struct btree *btree_node_alloc_replacement(struct btree *b,
>  {
>  	struct btree *n = bch_btree_node_alloc(b->c, op, b->level, b->parent);
>  
> -	if (!IS_ERR_OR_NULL(n)) {
> +	if (!IS_ERR(n)) {
>  		mutex_lock(&n->write_lock);
>  		bch_btree_sort_into(&b->keys, &n->keys, &b->c->sort);
>  		bkey_copy_key(&n->key, &b->key);
> @@ -1340,7 +1340,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
>  	memset(new_nodes, 0, sizeof(new_nodes));
>  	closure_init_stack(&cl);
>  
> -	while (nodes < GC_MERGE_NODES && !IS_ERR_OR_NULL(r[nodes].b))
> +	while (nodes < GC_MERGE_NODES && !IS_ERR(r[nodes].b))
>  		keys += r[nodes++].keys;
>  
>  	blocks = btree_default_blocks(b->c) * 2 / 3;
> @@ -1352,7 +1352,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
>  
>  	for (i = 0; i < nodes; i++) {
>  		new_nodes[i] = btree_node_alloc_replacement(r[i].b, NULL);
> -		if (IS_ERR_OR_NULL(new_nodes[i]))
> +		if (IS_ERR(new_nodes[i]))
>  			goto out_nocoalesce;
>  	}
>  
> @@ -1487,7 +1487,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
>  	bch_keylist_free(&keylist);
>  
>  	for (i = 0; i < nodes; i++)
> -		if (!IS_ERR_OR_NULL(new_nodes[i])) {
> +		if (!IS_ERR(new_nodes[i])) {
>  			btree_node_free(new_nodes[i]);
>  			rw_unlock(true, new_nodes[i]);
>  		}
> @@ -1669,7 +1669,7 @@ static int bch_btree_gc_root(struct btree *b, struct btree_op *op,
>  	if (should_rewrite) {
>  		n = btree_node_alloc_replacement(b, NULL);
>  
> -		if (!IS_ERR_OR_NULL(n)) {
> +		if (!IS_ERR(n)) {
>  			bch_btree_node_write_sync(n);
>  
>  			bch_btree_set_root(n);
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index ba3909bb6bea..7660962e7b8b 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1724,7 +1724,7 @@ static void cache_set_flush(struct closure *cl)
>  	if (!IS_ERR_OR_NULL(c->gc_thread))
>  		kthread_stop(c->gc_thread);
>  
> -	if (!IS_ERR_OR_NULL(c->root))
> +	if (!IS_ERR(c->root))
>  		list_add(&c->root->list, &c->btree_cache);
>  
>  	/*
> @@ -2088,7 +2088,7 @@ static int run_cache_set(struct cache_set *c)
>  
>  		err = "cannot allocate new btree root";
>  		c->root = __bch_btree_node_alloc(c, NULL, 0, true, NULL);
> -		if (IS_ERR_OR_NULL(c->root))
> +		if (IS_ERR(c->root))
>  			goto err;
>  
>  		mutex_lock(&c->root->write_lock);
> -- 
> 2.25.1
> 
>