[PATCH v6 07/39] mm: assert mmap lock held, use new flags API in vm_insert_page[s]

[Lorenzo Stoakes (ARM)]

The existing logic asserts that an mmap write lock is held, bizarrely, by
asserting that an mmap_read_trylock() fails (which is not the same thing).

Assert the mmap write lock here and switch to using the new VMA flags API
while here.

Note that the vma_start_write() is explicitly broken out from
vm_flags_set() here in order to use vma_set_flags() safely.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs at kernel.org>
---
 mm/memory.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 448342883e9d..a35cca09eb71 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2599,10 +2599,11 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
 
 	if (!range_in_vma(vma, addr, end))
 		return -EFAULT;
-	if (!(vma->vm_flags & VM_MIXEDMAP)) {
-		VM_WARN_ON_ONCE(mmap_read_trylock(vma->vm_mm));
-		VM_WARN_ON_ONCE(vma->vm_flags & VM_PFNMAP);
-		vm_flags_set(vma, VM_MIXEDMAP);
+	if (!vma_test(vma, VMA_MIXEDMAP_BIT)) {
+		mmap_assert_write_locked(vma->vm_mm);
+		VM_WARN_ON_ONCE(vma_test(vma, VMA_PFNMAP_BIT));
+		vma_start_write(vma);
+		vma_set_flags(vma, VMA_MIXEDMAP_BIT);
 	}
 	/* Defer page refcount checking till we're about to map that page. */
 	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
@@ -2675,10 +2676,11 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
 {
 	if (addr < vma->vm_start || addr >= vma->vm_end)
 		return -EFAULT;
-	if (!(vma->vm_flags & VM_MIXEDMAP)) {
-		BUG_ON(mmap_read_trylock(vma->vm_mm));
-		BUG_ON(vma->vm_flags & VM_PFNMAP);
-		vm_flags_set(vma, VM_MIXEDMAP);
+	if (!vma_test(vma, VMA_MIXEDMAP_BIT)) {
+		mmap_assert_write_locked(vma->vm_mm);
+		VM_WARN_ON_ONCE(vma_test(vma, VMA_PFNMAP_BIT));
+		vma_start_write(vma);
+		vma_set_flags(vma, VMA_MIXEDMAP_BIT);
 	}
 	return insert_page(vma, addr, page, vma->vm_page_prot, false);
 }

-- 
2.55.0