Re: [PATCH] cgroup: fix to allow mounting a hierarchy by name

From: Li Zefan
Date: Wed Dec 28 2011 - 01:10:21 EST

Li Zefan wrote:
> Tejun Heo wrote:
>> Hello, Li.
>> On Tue, Dec 27, 2011 at 10:10:37AM +0800, Li Zefan wrote:
>>> If we mount a hierarchy with a name specified, the name is unique,
>>> and we can use it to mount the hierarchy without specifying its
>>> set of subsystem names. This feature is documented is
>>> Documentation/cgroups/cgroups.txt section 2.3
>>> Here's an example:
>>> # mount -t cgroup -o cpuset,name=myhier xxx /cgroup1
>>> # mount -t cgroup -o name=myhier xxx /cgroup2
>>> But it was broken by commit 32a8cf235e2f192eb002755076994525cdbaa35a
>>> (cgroup: make the mount options parsing more accurate)
>>> This fixes the regression.
>> Hmmm... so that has been broken over a year and nobody complained? Is
>> there any valid use case where specifying mount path as all other
>> filesystems wouldn't work? Is this 'name' thing necessary at all?
>> Maybe we should rip it out instead of fixing it? We can just leave it
>> as non-functional name which does nothing but being visible in mount
>> listing.
> The "name" option was introduced along with the "none" option, so we
> can distinguish between different cgroup hierarchies which have no
> bound subsystems, like this:
> # mount -t cgroup -o none,name=hier1 xxx /cgroup1
> # mount -t cgroup -o none,name=hier2 xxx /cgroup2
> As the name is unique, we have this "mount by hierarchy name" feature.
> It looks reasonable, but I guess few people know this feature. We can
> live with it, as it only saves us some typing when mounting an existing


> hierarchy. On the other hand, removing this small feature can hardly
> result in code reduction.
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