On Wed, Jul 02, 2025 at 02:01:33PM +0200, David Hildenbrand wrote: > On 02.07.25 13:54, Harry Yoo wrote: > > On Mon, Jun 30, 2025 at 03:00:01PM +0200, David Hildenbrand wrote: > > > Instead, let's use a page flag. As the page flag can result in > > > false-positives, glue it to the page types for which we > > > support/implement movable_ops page migration. > > > > > > The flag reused by PageMovableOps() might be sued by other pages, so > > > warning in case it is set in page_has_movable_ops() might result in > > > false-positive warnings. > > > > > > Reviewed-by: Zi Yan <z...@nvidia.com> > > > Signed-off-by: David Hildenbrand <da...@redhat.com> > > > --- > > > > LGTM, > > Reviewed-by: Harry Yoo <harry....@oracle.com> > > > > With a question: is there any reason to change the page flag > > operations to use atomic bit ops? > > As we have the page lock in there, it's complicated. I thought about this > when writing that code, and was not able to convince myself that it is safe. > > But that was when I was prototyping and reshuffling patches, and we would > still have code that would clear the flag. > Given that we only allow setting the flag, it might be okay to use the > non-atomic variant as long as there can be nobody racing with us when > modifying flags. Especially trying to lock the folio concurrently is the big > problem. > > In isolate_movable_ops_page(), there is a comment about checking the flag > before grabbing the page lock, so that should be handled.
Right. > I'll have to check some other cases in balloon/zsmalloc code. Okay, it's totally fine to go with atomic version and then switching back to non atomic ops when we're sure it's safe. -- Cheers, Harry / Hyeonggon
