On 31.01.25 01:28, Alistair Popple wrote:
On Thu, Jan 30, 2025 at 04:57:39PM +1100, Alistair Popple wrote:
On Wed, Jan 29, 2025 at 12:54:01PM +0100, David Hildenbrand wrote:
[...]
-int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
- unsigned long end, struct page **pages,
- void *owner)
+struct page *make_device_exclusive(struct mm_struct *mm, unsigned long addr,
+ void *owner, struct folio **foliop)
{
- long npages = (end - start) >> PAGE_SHIFT;
- long i;
+ struct folio *folio;
+ struct page *page;
+ long npages;
+
+ mmap_assert_locked(mm);
- npages = get_user_pages_remote(mm, start, npages,
+ /*
+ * Fault in the page writable and try to lock it; note that if the
+ * address would already be marked for exclusive use by the device,
+ * the GUP call would undo that first by triggering a fault.
+ */
+ npages = get_user_pages_remote(mm, addr, 1,
FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
- pages, NULL);
- if (npages < 0)
- return npages;
-
- for (i = 0; i < npages; i++, start += PAGE_SIZE) {
- struct folio *folio = page_folio(pages[i]);
- if (PageTail(pages[i]) || !folio_trylock(folio)) {
- folio_put(folio);
- pages[i] = NULL;
- continue;
- }
+ &page, NULL);
+ if (npages != 1)
+ return ERR_PTR(npages);
+ folio = page_folio(page);
- if (!folio_make_device_exclusive(folio, mm, start, owner)) {
- folio_unlock(folio);
- folio_put(folio);
- pages[i] = NULL;
- }
+ if (!folio_test_anon(folio) || folio_test_hugetlb(folio)) {
+ folio_put(folio);
+ return ERR_PTR(-EOPNOTSUPP);
+ }
+
+ if (!folio_trylock(folio)) {
Actually I think we can make this folio_lock(folio) now. The only reason for
the trylock was to avoid deadlock between other threads looping over a range
of folios while holding folio locks which is something the migration code also
does.
Okay, let me do that in a separate patch. Thanks!
--
Cheers,
David / dhildenb
