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

From	Auger Eric <eric.auger@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v7 08/19] iommu: Implement reserved_regions iommu-group sysfs file
Date	2017-01-10 22:30 +0100
Message-ID	<sYc9s-6qU-49@gated-at.bofh.it> (permalink)
References	<sXIuJ-4Rr-3@gated-at.bofh.it> <sXIuL-4Rr-55@gated-at.bofh.it> <sY7t8-3Cj-25@gated-at.bofh.it> <sY8fw-47w-21@gated-at.bofh.it>
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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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[PATCH v7 08/19] iommu: Implement reserved_regions iommu-group sysfs file Eric Auger <eric.auger@redhat.com> - 2017-01-09 14:50 +0100
  Re: [PATCH v7 08/19] iommu: Implement reserved_regions iommu-group  sysfs file Auger Eric <eric.auger@redhat.com> - 2017-01-10 17:30 +0100
    Re: [PATCH v7 08/19] iommu: Implement reserved_regions iommu-group  sysfs file Joerg Roedel <joro@8bytes.org> - 2017-01-10 18:20 +0100
      Re: [PATCH v7 08/19] iommu: Implement reserved_regions iommu-group  sysfs file Auger Eric <eric.auger@redhat.com> - 2017-01-10 22:30 +0100

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