Re: [PATCH v3 1/4] hugetlb: Fix wrong use of nr_online_nodes

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 2022/4/14 6:04, Andrew Morton wrote:
On Wed, 13 Apr 2022 14:27:54 +0800 "liupeng (DM)" <liupeng256@xxxxxxxxxx> wrote:

On 2022/4/13 12:42, Andrew Morton wrote:
On Wed, 13 Apr 2022 03:29:12 +0000 Peng Liu<liupeng256@xxxxxxxxxx>  wrote:

Certain systems are designed to have sparse/discontiguous nodes. In
this case, nr_online_nodes can not be used to walk through numa node.
Also, a valid node may be greater than nr_online_nodes.

However, in hugetlb, it is assumed that nodes are contiguous. Recheck
all the places that use nr_online_nodes, and repair them one by one.

What are the runtime effects of this shortcoming?
.
For sparse/discontiguous nodes, the current code may treat a valid node
as invalid, and will fail to allocate all hugepages on a valid node that
"nid >= nr_online_nodes".

As David suggested:
if (tmp >= nr_online_nodes)
	goto invalid;

Just imagine node 0 and node 2 are online, and node 1 is offline. Assuming
that "node < 2" is valid is wrong.
So do you think we should backport thtis fix into earlier kernel releases?
.
I think it is not an urgent bug, because:
1) Qemu does not support sparse node so far, although there are some sparse-node
issues to make qemu support sparse node.
2) I don't find an actual normal machine that reports sparse-node and need to
use hugepages so far.

[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux