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

[Matthew Wilcox]

On Tue, Feb 02, 2021 at 04:31:33PM -0800, 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.

NACK.

The system may not _panic_, but it is clearly now _broken_.  The device
doesn't work, and so the system is useless.  You haven't really improved
anything here.  Just bloated the kernel with yet another _ONCE variable
that in a normal system will never ever ever be triggered.