The page is already alloc at ion_alloc function, ion_mmap map the alloced pages to user-space.
The default prot can be PTE_RDONLY. Take a look at here: set_pte_at() arch/arm64/include/asm: if (pte_dirty(pte) && pte_write(pte)) pte_val(pte) &= ~PTE_RDONLY; else pte_val(pte) |= PTE_RDONLY;
So with the dirty bit,it can improve the efficiency and donnot need to handle memory fault when use access.
Signed-off-by: Chen Feng puck.chen@hisilicon.com Signed-off-by: Wei Dong weidong2@hisilicon.com Reviewed-by: Zhuangluan Su suzhuangluan@hisilicon.com --- drivers/staging/android/ion/ion.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c index e237e9f..dba5942 100644 --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -1026,6 +1026,9 @@ static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) if (!(buffer->flags & ION_FLAG_CACHED)) vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+ /*Default writeable*/ + vma->vm_page_prot = pte_mkdirty(vma->vm_page_prot); + mutex_lock(&buffer->lock); /* now map it to userspace */ ret = buffer->heap->ops->map_user(buffer->heap, buffer, vma);