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SubjectRe: [PATCH RFC] driver core: ensure a device has valid node id in device_add()
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On 2019/9/5 13:57, Greg KH wrote:
> On Thu, Sep 05, 2019 at 09:33:50AM +0800, Yunsheng Lin wrote:
>> Currently a device does not belong to any of the numa nodes
>> (dev->numa_node is NUMA_NO_NODE) when the FW does not provide
>> the node id and the device has not no parent device.
>>
>> According to discussion in [1]:
>> Even if a device's numa node is not set by fw, the device
>> really does belong to a node.
>>
>> This patch sets the device node to node 0 in device_add() if
>> the fw has not specified the node id and it either has no
>> parent device, or the parent device also does not have a valid
>> node id.
>>
>> There may be explicit handling out there relying on NUMA_NO_NODE,
>> like in nvme_probe().
>>
>> [1] https://lkml.org/lkml/2019/9/2/466
>>
>> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
>> ---
>> drivers/base/core.c | 17 ++++++++++++++---
>> include/linux/numa.h | 2 ++
>> 2 files changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>> index 1669d41..466b8ff 100644
>> --- a/drivers/base/core.c
>> +++ b/drivers/base/core.c
>> @@ -2107,9 +2107,20 @@ int device_add(struct device *dev)
>> if (kobj)
>> dev->kobj.parent = kobj;
>>
>> - /* use parent numa_node */
>> - if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
>> - set_dev_node(dev, dev_to_node(parent));
>> + /* use parent numa_node or default node 0 */
>> + if (!numa_node_valid(dev_to_node(dev))) {
>> + int nid = parent ? dev_to_node(parent) : NUMA_NO_NODE;
>
> Can you expand this to be a "real" if statement please?

Sure. May I ask why "? :" is not appropriate here?

>
>> +
>> + if (numa_node_valid(nid)) {
>> + set_dev_node(dev, nid);
>> + } else {
>> + if (nr_node_ids > 1U)
>> + pr_err("device: '%s': has invalid NUMA node(%d)\n",
>> + dev_name(dev), dev_to_node(dev));
>
> dev_err() will show you the exact device properly, instead of having to
> rely on dev_name().
>
> And what is a user to do if this message happens? How do they fix this?
> If they can not, what good is this error message?

If user know about their system's topology well enough and node 0
is not the nearest node to the device, maybe user can readjust that by
writing the nearest node to /sys/class/pci_bus/XXXX/device/numa_node,
if not, then maybe user need to contact the vendor for info or updates.

Maybe print error message as below:

dev_err(dev, FW_BUG "has invalid NUMA node(%d). Readjust it by writing to sysfs numa_node or contact your vendor for updates.\n",
dev_to_node(dev));

>
> thanks,
>
> greg k-h
>
> .
>

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