Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <167875238571.8008.9808655454439667586@noble.neil.brown.name>
 <CALTww2916uiO8_ViJQXutO2BPasFmiUJtfz8MxW0HKjDzwGFeQ@mail.gmail.com>
 <167945548970.8008.8910680813298326328@noble.neil.brown.name>
 <168012671413.8106.6812573281942242445@noble.neil.brown.name>
 <CALTww28X1NQecTY3Jbkz_wbHc_N7GOw3hJLEyb2YnxAmQ8PRFw@mail.gmail.com> <168014613094.14629.7292916705339147692@noble.neil.brown.name>
In-Reply-To: <168014613094.14629.7292916705339147692@noble.neil.brown.name>
From:   Xiao Ni <xni@redhat.com>
Date:   Thu, 30 Mar 2023 12:55:07 +0800
Message-ID: <CALTww29CN4iqmneiAG31kZDBubCMop=gg299hdW-TXCNq1c4gQ@mail.gmail.com>
Subject: Re: [PATCH - mdadm] mdopen: always try create_named_array()
To:     NeilBrown <neilb@suse.de>
Cc:     Jes Sorensen <jes@trained-monkey.org>,
        Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>,
        Song Liu <song@kernel.org>,
        Linux regressions mailing list <regressions@lists.linux.dev>,
        linux-raid <linux-raid@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Nikolay Kichukov <hijacker@oldum.net>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Thu, Mar 30, 2023 at 11:15=E2=80=AFAM NeilBrown <neilb@suse.de> wrote:
>
> On Thu, 30 Mar 2023, Xiao Ni wrote:
> > On Thu, Mar 30, 2023 at 5:52=E2=80=AFAM NeilBrown <neilb@suse.de> wrote=
:
> > >
> > > On Wed, 22 Mar 2023, NeilBrown wrote:
> > > > On Wed, 22 Mar 2023, Xiao Ni wrote:
> > > >
> > > > >
> > > > > Second, are there possibilities that the arguments "dev" and "nam=
e" of
> > > > > function create_mddev
> > > > > are null at the same time?
> > > >
> > > > No.  For Build or Create, dev is never NULL.  For Assemble and
> > > > Incremental, name is never NULL.
> > > >
> > >
> > > I should clarify this a bit.  For Assemble and Incremental, "name" is
> > > never NULL *but* it might be an empty string.
> > > So:
> > >         if (name && name[0] =3D=3D 0)
> > >                 name =3D NULL;
> > >
> > > might cause it to become NULL.  So you cannot assume there is always
> > > either a valid "dev" or a valid "name".  "dev" might be NULL, and "na=
me"
> > > might be "".
> > >
> > > NeilBrown
> > >
> >
> > Hi Neil
> >
> > The input argument name should be the metadata name. For incremental
> > and assemble, why are there possibilities that the metadata name is
> > invalid? A raid device should have a valid metadata name, right?
>
> "should" do, yes.  But you can never completely trust data on disk.  It
> is safest to be prepared for "name" being "".
>
> NeilBrown
>

That's right, thanks for this explanation :)

--=20
Best Regards
Xiao Ni