Re: [PATCH 1/2] mm: replace BUG_ON in vm_insert_page with a return of an error

Hi: On 2021/2/3 8:31, Suren Baghdasaryan wrote:

Replace BUG_ON(vma->vm_flags & VM_PFNMAP) in vm_insert_page with WARN_ON_ONCE and returning an error. This is to ensure users of the vm_insert_page that set VM_PFNMAP are notified of the wrong flag usage and get an indication of an error without panicing the kernel. This will help identifying drivers that need to clear VM_PFNMAP before using dmabuf system heap which is moving to use vm_insert_page.

Suggested-by: Christoph Hellwig hch@infradead.org Signed-off-by: Suren Baghdasaryan surenb@google.com

Looks reasonable. Thanks. Reviewed-by: Miaohe Lin linmiaohe@huawei.com

---

mm/memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c index feff48e1465a..e503c9801cd9 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1827,7 +1827,8 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, return -EINVAL; if (!(vma->vm_flags & VM_MIXEDMAP)) { BUG_ON(mmap_read_trylock(vma->vm_mm));

• BUG_ON(vma->vm_flags & VM_PFNMAP);
  

• if (WARN_ON_ONCE(vma->vm_flags & VM_PFNMAP))
  

• 	return -EINVAL;
  

  vma->vm_flags |= VM_MIXEDMAP; } return insert_page(vma, addr, page, vma->vm_page_prot);