linux-kernel - Re: [PATCH v1] driver core: Use list_del_init to replace list_del at device_links

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Message-ID: <4b185c9f-7fa2-349d-9f72-3c787ac30377@huawei.com>
Date:   Wed, 8 Jan 2020 16:08:44 +0000
From:   John Garry <john.garry@...wei.com>
To:     James Bottomley <jejb@...ux.ibm.com>,
        Greg KH <gregkh@...uxfoundation.org>
CC:     luojiaxing <luojiaxing@...wei.com>,
        "saravanak@...gle.com" <saravanak@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v1] driver core: Use list_del_init to replace list_del at
 device_links_purge()

On 08/01/2020 16:01, James Bottomley wrote:
>>>> 	cdev->dev = NULL;
>>>> 			return device_add(&cdev->cdev);
>>>> 		}
>>>> 	}
>>>> 	return -ENODEV;
>>>> }
>>> The design of the code is simply to remove the link to the inserted
>>> device which has been removed.
>>>
>>> I*think*  this means the calls to device_del and device_add are
>>> unnecessary and should go.  enclosure_remove_links and the put of
>>> the
>>> enclosed device should be sufficient.
>> That would make more sense than trying to "reuse" the device
>> structure
>> here by tearing it down and adding it back.
> OK, let's try that.  This should be the patch if someone can try it
> (I've compile tested it, but the enclosure system is under a heap of
> stuff in the garage).

I can test it now.

But it is a bit suspicious that we had the device_del() and device_add() 
at all, especially since the code change makes it look a bit more like 
pre-43d8eb9cfd0 ("ses: add support for enclosure component hot removal")

John

> 
> James
> 
> ---
> 
> diff --git a/drivers/misc/enclosure.c b/drivers/misc/enclosure.c
> index 6d27ccfe0680..3c2d405bc79b 100644
> --- a/drivers/misc/enclosure.c
> +++ b/drivers/misc/enclosure.c
> @@ -406,10 +406,9 @@ int enclosure_remove_device(struct enclosure_device *edev, struct device *dev)
>   		cdev = &edev->component[i];
>   		if (cdev->dev == dev) {
>   			enclosure_remove_links(cdev);
> -			device_del(&cdev->cdev);
>   			put_device(dev);
>   			cdev->dev = NULL;
> -			return device_add(&cdev->cdev);
> +			return 0;
>   		}
>   	}
>   	return -ENODEV;