This code was written by Matt Brost. This is a placeholder until his
patch is available.

Cc: Matthew Brost <[email protected]>
Signed-off-by: Francois Dugast <[email protected]>
---
 drivers/gpu/drm/drm_pagemap.c | 36 ++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
index db3795f03aca..05e708730132 100644
--- a/drivers/gpu/drm/drm_pagemap.c
+++ b/drivers/gpu/drm/drm_pagemap.c
@@ -452,6 +452,39 @@ static int drm_pagemap_migrate_range(struct 
drm_pagemap_devmem *devmem,
        return ret;
 }
 
+/**
+ * drm_pagemap_cpages() - Count collected pages
+ * @migrate_pfn: Array of migrate_pfn entries to account
+ * @npages: Number of entries in @migrate_pfn
+ *
+ * Compute the total number of minimum-sized pages represented by the
+ * collected entries in @migrate_pfn. The total is derived from the
+ * order encoded in each entry.
+ *
+ * Return: Total number of minimum-sized pages.
+ */
+static int drm_pagemap_cpages(unsigned long *migrate_pfn, unsigned long npages)
+{
+       unsigned long i, cpages = 0;
+
+       for (i = 0; i < npages;) {
+               struct page *page = migrate_pfn_to_page(migrate_pfn[i]);
+               struct folio *folio;
+               unsigned int order = 0;
+
+               if (!page)
+                       goto next;
+
+               folio = page_folio(page);
+               order = folio_order(folio);
+               cpages += NR_PAGES(order);
+next:
+               i += NR_PAGES(order);
+       }
+
+       return cpages;
+}
+
 /**
  * drm_pagemap_migrate_to_devmem() - Migrate a struct mm_struct range to 
device memory
  * @devmem_allocation: The device memory allocation to migrate to.
@@ -554,7 +587,8 @@ int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem 
*devmem_allocation,
                goto err_free;
        }
 
-       if (migrate.cpages != npages) {
+       if (migrate.cpages != npages &&
+           drm_pagemap_cpages(migrate.src, npages) != npages) {
                /*
                 * Some pages to migrate. But we want to migrate all or
                 * nothing. Raced or unknown device pages.
-- 
2.43.0

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