On Fri, Dec 08, 2023 at 04:23:35PM +0800, linan666@xxxxxxxxxxxxxxx wrote:
> From: Li Nan <linan122@xxxxxxxxxx>
>
> "if device_add() succeeds, you should call device_del() when you want to
> get rid of it."
>
> In sd_probe(), device_add_disk() fails when device_add() has already
> succeeded, so change put_device() to device_unregister() to ensure device
> resources are released.
>
> Fixes: 2a7a891f4c40 ("scsi: sd: Add error handling support for add_disk()")
> Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
Nacked-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> ---
> drivers/scsi/sd.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 542a4bbb21bc..d81cbeee06eb 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -3736,7 +3736,7 @@ static int sd_probe(struct device *dev)
>
> error = device_add_disk(dev, gd, NULL);
> if (error) {
> - put_device(&sdkp->disk_dev);
> + device_unregister(&sdkp->disk_dev);
> put_disk(gd);
> goto out;
> }
This is incorrect, device_unregister() calls:
void device_unregister(struct device *dev)
{
pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
device_del(dev);
put_device(dev);
}
So you're adding what you believe to be a correct missing device_del().
But what you missed is that if device_add_disk() fails then device_add()
did not succeed because the new code we have in the kernel *today* unwinds
this for us now.
What you missed is that in today's code inside device_add_disk(), if
device_add() succeeeds we now unwind and call device_del() for the
device for you. And so, quoting the next sentence you took from
device_add():
"If device_add() has *not* succeeded, use *only* put_device() to drop the
reference count."
Please do reference in the future a crash dump / or explain how you
reached your conclusions if you do not have a crash dump to prove an
issue. Specially if you are suggesting it Fixes a commit.
Luis
