Re: [PATCH v7 1/7] mm: pass task and mm to do_madvise

[Minchan Kim]

On Thu, Mar 05, 2020 at 04:48:12PM +0100, Vlastimil Babka wrote:
> On 3/2/20 8:36 PM, Minchan Kim wrote:
> > In upcoming patches, do_madvise will be called from external process
> > context so we shouldn't asssume "current" is always hinted process's
> > task_struct.
> 
> 
> > Furthermore, we couldn't access mm_struct via task->mm
> > once it's verified by access_mm which will be introduced in next
> > patch[1].
> 
> I would suggest to replace with:
> 
> Furthermore, we must not access mm_struct via task->mm, but obtain it via
> access_mm() once (in the following patch) and only use that pointer [1], so pass
> it to do_madvise() as well. Note the vma->vm_mm pointers are safe, so we can use
> them further down the call stack.
> 
> > And let's pass *current* and current->mm as arguments of
> > do_madvise so it shouldn't change existing behavior but prepare
> > next patch to make review easy.
> > 
> > Note: io_madvise pass NULL as target_task argument of do_madvise
> > because it couldn't know who is target.
> 
>              can't

Andrew already picked up your suggestion except "can't" part. I don't
think it's enough to resend fix it so I will leave it as-is.