[libvirt PATCH 1/3] vircgroup: introduce virCgroupGetInode function

[Michal Prívozník]

On 8/4/21 10:22 AM, Pavel Hrdina wrote:
> On Wed, Aug 04, 2021 at 10:06:17AM +0200, Michal Prívozník wrote:
>> On 8/3/21 4:29 PM, Pavel Hrdina wrote:
>>> For new feature Fibre Channel VMID we will need to get inode of the
>>> VM root cgroup as it is used in the new kernel API together with VMID.
>>>
>>> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
>>> ---
>>>  src/libvirt_private.syms |  1 +
>>>  src/util/vircgroup.c     | 37 +++++++++++++++++++++++++++++++++++++
>>>  src/util/vircgroup.h     |  2 ++
>>>  3 files changed, 40 insertions(+)
>>>
>>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>>> index 6961cdb137..d8451fcfff 100644
>>> --- a/src/libvirt_private.syms
>>> +++ b/src/libvirt_private.syms
>>> @@ -1920,6 +1920,7 @@ virCgroupGetCpuShares;
>>>  virCgroupGetDevicePermsString;
>>>  virCgroupGetDomainTotalCpuStats;
>>>  virCgroupGetFreezerState;
>>> +virCgroupGetInode;
>>>  virCgroupGetMemoryHardLimit;
>>>  virCgroupGetMemorySoftLimit;
>>>  virCgroupGetMemoryStat;
>>> diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
>>> index 1b3b28342e..ea702e7b63 100644
>>> --- a/src/util/vircgroup.c
>>> +++ b/src/util/vircgroup.c
>>> @@ -3973,3 +3973,40 @@ virCgroupGetCpuPeriodQuota(virCgroup *cgroup, unsigned long long *period,
>>>  
>>>      return 0;
>>>  }
>>> +
>>> +
>>> +/**
>>> + * virCgroupGetInode:
>>> + *
>>> + * @cgroup: the cgroup to get inode for
>>> + *
>>> + * Get the @cgroup inode and return its value to the caller.
>>> + *
>>> + * Returns inode on success, -1 on error with error message reported.
>>> + */
>>> +int
>>> +virCgroupGetInode(virCgroup *cgroup)
>>> +{
>>> +    VIR_AUTOCLOSE fd = 0;
>>> +    struct stat st;
>>> +    int controller = virCgroupGetAnyController(cgroup);
>>> +    g_autofree char *path = NULL;
>>> +
>>> +    if (controller < 0)
>>> +        return -1;
>>> +
>>> +    if (virCgroupPathOfController(cgroup, controller, "", &path) < 0)
>>> +        return -1;
>>> +
>>> +    if ((fd = open(path, O_RDONLY | O_NONBLOCK)) < 0) {
>>> +        virReportSystemError(errno, _("failed to open cgroup '%s'"), path);
>>> +        return -1;
>>> +    }
>>
>> Is the open() necessary? Why isn't plain stat() enough?
> 
> Good question :) I was lazy so I looked for first similar code in
> libvirt codebase and copied it. You are right, stat should be enough
> as according to man page stat and fstat are identical except or the
> fd vs path parameter. I'll fix it before pushing or should I send a v2?

No need, just drop open() and switch to stat() before pushing. My
Reviewed-by still applies.

Michal