linux-kernel - Re: [PATCH v7 08/19] iommu: Implement reserved_regions iommu-group sysfs file

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Message-ID: <1d2137bf-8d0d-d786-6cd6-9090fb76f05c@redhat.com>
Date:   Tue, 10 Jan 2017 22:21:28 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     drjones@...hat.com, jason@...edaemon.net, kvm@...r.kernel.org,
        marc.zyngier@....com, bharat.bhushan@....com,
        punit.agrawal@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        geethasowjanya.akula@...il.com, diana.craciun@....com,
        alex.williamson@...hat.com, pranav.sawargaonkar@...il.com,
        shankerd@...eaurora.org, linux-arm-kernel@...ts.infradead.org,
        tglx@...utronix.de, gpkulkarni@...il.com, robin.murphy@....com,
        christoffer.dall@...aro.org, eric.auger.pro@...il.com
Subject: Re: [PATCH v7 08/19] iommu: Implement reserved_regions iommu-group
 sysfs file

Hi Joerg,
On 10/01/2017 18:14, Joerg Roedel wrote:
> On Tue, Jan 10, 2017 at 05:20:34PM +0100, Auger Eric wrote:
>> The /sys/kernel/iommu_groups/n directory seems to be removed before this
>> gets called and this may produce a WARNING when devices get removed from
>> the group. I intend to remove the call since I have the feeling
>> everything gets cleaned up properly.
> 
> A feeling is not enough, please check that in the code.

So my understanding is on group's kobject_release we have:
kobject_release
|_ kobject_cleanup
	|_ kobject_del
		|_ sysfs_remove_dir
			|_ kernfs_remove
				|_ _kernfs_remove
	../..
	|_ ktype release (iommu_group_release)

_kernfs_remove() calls kernfs_put() on all descendant nodes, leading to
the whole directory cleanup.

In iommu_group_release I called sysfs_remove_file on the
reserved_regions attribute file. My understanding is its job is
identifical as what was done previously and the node was already
destroyed hence the warning.

sysfs_remove_file
|_ sysfs_remove_file_ns
	|_ kernfs_remove_by_name_ns
		|_kernfs_remove

So my understanding is it is safe to remove it.

Thanks

Eric
> 
> 
> 	Joerg
> 
> 
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> linux-arm-kernel@...ts.infradead.org
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> 

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