5 Aug
2022
5 Aug
'22
6:06 p.m.
On 05.08.22 19:55, Paolo Bonzini wrote:
On 7/21/22 11:44, David Hildenbrand wrote:
Also, I*think* you can place pages via userfaultfd into shmem. Not sure if that would count "auto alloc", but it would certainly bypass fallocate().
Yeah, userfaultfd_register would probably have to forbid this for F_SEAL_AUTO_ALLOCATE vmas. Maybe the memfile_node can be reused for this, adding a new MEMFILE_F_NO_AUTO_ALLOCATE flags? Then userfault_register would do something like memfile_node_get_flags(vma->vm_file) and check the result.
An alternative is to simply have the shmem allocation fail in a similar way. Maybe it does already, I haven't checked (don't think so).
--
Thanks,
David / dhildenb