On Thu, Jun 08, 2023 at 01:49:27PM -0700, Mike Kravetz wrote:
This effectively reverts commit 16c243e99d33 ("udmabuf: Add support for mapping hugepages (v4)"). Recently, Junxiao Chang found a BUG with page map counting as described here [1]. This issue pointed out that the udmabuf driver was making direct use of subpages of hugetlb pages. This is not a good idea, and no other mm code attempts such use. In addition to the mapcount issue, this also causes issues with hugetlb vmemmap optimization and page poisoning.
For now, remove hugetlb support.
If udmabuf wants to be used on hugetlb mappings, it should be changed to only use complete hugetlb pages. This will require different alignment and size requirements on the UDMABUF_CREATE API.
[1] https://lore.kernel.org/linux-mm/20230512072036.1027784-1-junxiao.chang@inte...
Fixes: 16c243e99d33 ("udmabuf: Add support for mapping hugepages (v4)") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com
Acked-by: Gerd Hoffmann kraxel@redhat.com