Re: [PATCH v3] mm: fix unexpected changes to {failslab|fail_page_alloc}.attr

[Qi Zheng]

On 2022/11/19 05:42, Andrew Morton wrote:
> On Fri, 18 Nov 2022 18:00:11 +0800 Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
>
> > When we specify __GFP_NOWARN, we only expect that no warnings
> > will be issued for current caller. But in the __should_failslab()
> > and __should_fail_alloc_page(), the local GFP flags alter the
> > global {failslab|fail_page_alloc}.attr, which is persistent and
> > shared by all tasks. This is not what we expected, let's fix it.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
> > Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> > Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> > Reviewed-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> >
> > ...
> >
> > -bool should_fail(struct fault_attr *attr, ssize_t size)
> > +bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
> >   {
> >   	bool stack_checked = false;
> >   
> > @@ -152,13 +149,20 @@ bool should_fail(struct fault_attr *attr, ssize_t size)
> >   		return false;
> >   
> >   fail:
> > -	fail_dump(attr);
> > +	if (!(flags & FAULT_NOWARN))
> > +		fail_dump(attr);
> >   
> >   	if (atomic_read(&attr->times) != -1)
> >   		atomic_dec_not_zero(&attr->times);
> >   
> >   	return true;
> >   }
> > +EXPORT_SYMBOL_GPL(should_fail_ex);
>
> I don't see a need to export this?

Yes, my initial thought was that there might be a driver using this
function, but there really isn't one yet.

And I see you've helped remove this, thanks a lot. :)

>

--
Thanks,
Qi