On Mon, 10 Feb 2025 20:37:45 +0100 David Hildenbrand [off-list ref] wrote:

The single "real" user in the tree of make_device_exclusive_range() always
requests making only a single address exclusive. The current implementation
is hard to fix for properly supporting anonymous THP / large folios and
for avoiding messing with rmap walks in weird ways.

So let's always process a single address/page and return folio + page to
minimize page -> folio lookups. This is a preparation for further
changes.

Reject any non-anonymous or hugetlb folios early, directly after GUP.

While at it, extend the documentation of make_device_exclusive() to
clarify some things.

x86_64 allmodconfig:

drivers/gpu/drm/nouveau/nouveau_svm.c: In function 'nouveau_atomic_range_fault':
drivers/gpu/drm/nouveau/nouveau_svm.c:612:68: error: 'folio' undeclared (first use in this function)
  612 |                 page = make_device_exclusive(mm, start, drm->dev, &folio);
      |                                                                    ^~~~~
drivers/gpu/drm/nouveau/nouveau_svm.c:612:68: note: each undeclared identifier is reported only once for each function it appears in