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From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     Dan Carpenter <dan.carpenter@oracle.com>,
        Christoph Hellwig <hch@infradead.org>
Cc:     Wenchao Hao <haowenchao@huawei.com>, axboe@kernel.dk,
        jejb@linux.ibm.com, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
        martin.petersen@oracle.com,
        syzbot+f08c77040fa163a75a46@syzkaller.appspotmail.com,
        syzkaller-bugs@googlegroups.com, linfeilong@huawei.com
Subject: Re: [PATCH] scsi: sd: call device_del() if device_add_disk() fails
Date:   Thu, 31 Mar 2022 11:07:45 +0200
Message-ID: <10056508.nUPlyArG6x@leap>
In-Reply-To: <YkU/6KB+0fPU5Hie@infradead.org>
References: <20220329154948.10350-1-fmdefrancesco@gmail.com> <20220331054156.GI3293@kadam> <YkU/6KB+0fPU5Hie@infradead.org>
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On gioved=C3=AC? 31 marzo 2022 07:45:12 CEST Christoph Hellwig wrote:
> > The temptation was to call device_unregister() which is a combined
> > device_del(); device_put(); but when the device_initialize() and
> > device_add() are called separately, then I think it is more readable to
> > call del and put separately as well.
>=20
> I think we should also consolidate the initialization side.  Using
> device_register and device_unregister would have prevented this bug
> and I should have switched to that before refactoring the code.
>=20
If I don't misunderstand what you wrote, I think you mean something like
the following changes:

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index a390679cf458..7a000a9a9dbe 100644
=2D-- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3431,7 +3431,7 @@ static int sd_probe(struct device *dev)
        sdkp->disk_dev.class =3D &sd_disk_class;
        dev_set_name(&sdkp->disk_dev, "%s", dev_name(dev));
=20
=2D       error =3D device_add(&sdkp->disk_dev);
+       error =3D device_register(&sdkp->disk_dev);
        if (error) {
                put_device(&sdkp->disk_dev);
                goto out;
@@ -3474,7 +3474,7 @@ static int sd_probe(struct device *dev)
=20
        error =3D device_add_disk(dev, gd, NULL);
        if (error) {
=2D               put_device(&sdkp->disk_dev);
+               device_unregister(&sdkp->disk_dev);
                goto out;
        }

@Dan, @Christoph: what do you think of the changes that I've copy-pasted ab=
ove?

Thanks,

=46abio M. De Francesco