linux-kernel - Re: [RFC 2/7] mm/vmalloc: Support non-blocking GFP flags in alloc_vmap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aG02jeuCSPUFBx7C@tiehlicka>
Date: Tue, 8 Jul 2025 17:17:33 +0200
From: Michal Hocko <mhocko@...e.com>
To: Uladzislau Rezki <urezki@...il.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Baoquan He <bhe@...hat.com>
Subject: Re: [RFC 2/7] mm/vmalloc: Support non-blocking GFP flags in
 alloc_vmap_area()

On Tue 08-07-25 14:34:28, Uladzislau Rezki wrote:
> On Mon, Jul 07, 2025 at 09:11:35AM +0200, Michal Hocko wrote:
> > On Fri 04-07-25 17:25:32, Uladzislau Rezki wrote:
> > [...]
> > > @@ -2030,7 +2033,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> > >  	 */
> > >  	va = node_alloc(size, align, vstart, vend, &addr, &vn_id);
> > >  	if (!va) {
> > > -		gfp_mask = gfp_mask & GFP_RECLAIM_MASK;
> > > +		if (allow_block)
> > > +			gfp_mask = gfp_mask & GFP_RECLAIM_MASK;
> > 
> > I don't follow here and is this even correct?
> > 
> Allow nested flags to follow a user request if there is a request
> to not block. For example if we apply GFP_RECLAIM_MASK to GFP_ATOMIC
> GFP_ATOMIC is converted to zero, thus to GFP_NOWAIT.

I still do not follow. The aim of this code is to filter out all
non-reclaim related flags. Why that should work differently for
non-waiting allocations?
Btw. if you had GPP_ATOMIC the resulting mask will be still GFP_ATOMIC
as both __GFP_HIGH|__GFP_KSWAPD_RECLAIM are part of GFP_RECLAIM_MASK.

-- 
Michal Hocko
SUSE Labs