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Subject: Re: [PATCH] bcache: Remove some unnecessary NULL point check for the
 return value of __bch_btree_node_alloc-related pointer
From:   Coly Li <colyli@suse.de>
In-Reply-To: <CAJedcCzNB+1byPEzEgQ6ELjeoRQcZ=GnZg+1J4+FZvfnoK0H2Q@mail.gmail.com>
Date:   Fri, 3 Feb 2023 10:46:00 +0800
Cc:     Zheng Wang <zyytlz.wz@163.com>, stable@vger.kernel.org,
        Kent Overstreet <kent.overstreet@gmail.com>,
        linux-bcache@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        alex000young@gmail.com
Content-Transfer-Encoding: quoted-printable
Message-Id: <1A4D30F2-5FCB-4498-9571-12B320F4E1A1@suse.de>
References: <20230203022759.576832-1-zyytlz.wz@163.com>
 <CAJedcCzNB+1byPEzEgQ6ELjeoRQcZ=GnZg+1J4+FZvfnoK0H2Q@mail.gmail.com>
To:     Zheng Hacker <hackerzheng666@gmail.com>
Precedence: bulk


> 2023=E5=B9=B42=E6=9C=883=E6=97=A5 10:43=EF=BC=8CZheng Hacker =
<hackerzheng666@gmail.com> =E5=86=99=E9=81=93=EF=BC=9A
>=20
> Hello,
>=20
> After writing the patch, I found there may be more places to replace
> IS_ERR_OR_NULL to IS_ERR.
> If the alloc of node will never be NULL, the additional NULL check of
> nodes after allocation may also
> be useless. This patch just fixes the check around the alloc. I'm not
> sure about other places for my
> limited understanding of the code in bcache.

This was why I suggested you to post an extra cleanup patch like this.

You may just add more changes as you mentioned into this patch and post =
another updated version.

Thanks.

Coly Li

>=20
> Thanks,
> Zheng Wang
>=20
> Zheng Wang <zyytlz.wz@163.com> =E4=BA=8E2023=E5=B9=B42=E6=9C=883=E6=97=A5=
=E5=91=A8=E4=BA=94 10:28=E5=86=99=E9=81=93=EF=BC=9A
>>=20
>> 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.
>>=20
>> Fixes: cafe56359144 ("bcache: A block layer cache")
>> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
>> ---
>> drivers/md/bcache/btree.c | 6 +++---
>> drivers/md/bcache/super.c | 2 +-
>> 2 files changed, 4 insertions(+), 4 deletions(-)
>>=20
>> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
>> index 147c493a989a..417cd7c436c4 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 =3D bch_btree_node_alloc(b->c, op, b->level, =
b->parent);
>>=20
>> -       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);
>> @@ -1352,7 +1352,7 @@ static int btree_gc_coalesce(struct btree *b, =
struct btree_op *op,
>>=20
>>        for (i =3D 0; i < nodes; i++) {
>>                new_nodes[i] =3D 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;
>>        }
>>=20
>> @@ -1669,7 +1669,7 @@ static int bch_btree_gc_root(struct btree *b, =
struct btree_op *op,
>>        if (should_rewrite) {
>>                n =3D btree_node_alloc_replacement(b, NULL);
>>=20
>> -               if (!IS_ERR_OR_NULL(n)) {
>> +               if (!IS_ERR(n)) {
>>                        bch_btree_node_write_sync(n);
>>=20
>>                        bch_btree_set_root(n);
>> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
>> index ba3909bb6bea..92de714fe75e 100644
>> --- a/drivers/md/bcache/super.c
>> +++ b/drivers/md/bcache/super.c
>> @@ -2088,7 +2088,7 @@ static int run_cache_set(struct cache_set *c)
>>=20
>>                err =3D "cannot allocate new btree root";
>>                c->root =3D __bch_btree_node_alloc(c, NULL, 0, true, =
NULL);
>> -               if (IS_ERR_OR_NULL(c->root))
>> +               if (IS_ERR(c->root))
>>                        goto err;
>>=20
>>                mutex_lock(&c->root->write_lock);
>> --
>> 2.25.1
>>=20