Re: [PATCH 1/2] mm: replace BUG_ON in vm_insert_page with a return of an error
From: Miaohe Lin <linmiaohe@huawei.com>
Date: 2021-02-03 01:27:55
Also in:
dri-devel, linux-mm, lkml
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>
quoted hunk ↗ jump to hunk
--- 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);