[PATCH v3 4/6] drm/gem-shmem: Refactor drm_gem_shmem_try_map_pmd()

[Thomas Zimmermann <tzimmermann@suse.de>]

The current mmap page-fault handler requires some changes before it
can track folio access.

Call to folio_test_pmd_mappable() into the mmap page-fault handler
before calling drm_gem_shmem_try_map_pmd(). The folio will become
useful for tracking the access status.

Also rename drm_gem_shmem_try_map_pmd() to _try_insert_pfn_pmd()
and only pass the page fault and page-frame number. The new name and
parameters make it similar to vmf_insert_pfn_pmd().

No functional changes. If PMD mapping fails or is not supported,
insert a regular PFN as before.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index ab8e331005f9..c3a054899ba3 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -550,17 +550,14 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
 
-static vm_fault_t drm_gem_shmem_try_map_pmd(struct vm_fault *vmf, unsigned long addr,
-					    struct page *page)
+static vm_fault_t drm_gem_shmem_try_insert_pfn_pmd(struct vm_fault *vmf, unsigned long pfn)
 {
 #ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
-	unsigned long pfn = page_to_pfn(page);
 	unsigned long paddr = pfn << PAGE_SHIFT;
-	bool aligned = (addr & ~PMD_MASK) == (paddr & ~PMD_MASK);
+	bool aligned = (vmf->address & ~PMD_MASK) == (paddr & ~PMD_MASK);
 
-	if (aligned &&
-	    pmd_none(*vmf->pmd) &&
-	    folio_test_pmd_mappable(page_folio(page))) {
+	if (aligned && pmd_none(*vmf->pmd)) {
+		/* Read-only mapping; split upon write fault */
 		pfn &= PMD_MASK >> PAGE_SHIFT;
 		return vmf_insert_pfn_pmd(vmf, pfn, false);
 	}
@@ -580,6 +577,7 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
 	struct page **pages = shmem->pages;
 	pgoff_t page_offset = vmf->pgoff - vma->vm_pgoff; /* page offset within VMA */
 	struct page *page;
+	struct folio *folio;
 	unsigned long pfn;
 
 	dma_resv_lock(obj->resv, NULL);
@@ -591,15 +589,16 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
 	page = pages[page_offset];
 	if (drm_WARN_ON_ONCE(dev, !page))
 		goto out;
-
-	ret = drm_gem_shmem_try_map_pmd(vmf, vmf->address, page);
-	if (ret == VM_FAULT_NOPAGE)
-		goto out;
+	folio = page_folio(page);
 
 	pfn = page_to_pfn(page);
-	ret = vmf_insert_pfn(vma, vmf->address, pfn);
 
- out:
+	if (folio_test_pmd_mappable(folio))
+		ret = drm_gem_shmem_try_insert_pfn_pmd(vmf, pfn);
+	if (ret != VM_FAULT_NOPAGE)
+		ret = vmf_insert_pfn(vma, vmf->address, pfn);
+
+out:
 	dma_resv_unlock(obj->resv);
 
 	return ret;
-- 
2.52.0