linux-kernel - Re: [RESEND PATCH v1] mm/vmalloc: fix page mapping if vm_area_alloc_pages() with high order fallback to order 0

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Message-ID: <Zr97CW+Y4FiviI35@MiWiFi-R3L-srv>
Date: Sat, 17 Aug 2024 00:15:05 +0800
From: Baoquan He <bhe@...hat.com>
To: Uladzislau Rezki <urezki@...il.com>
Cc: Hailong Liu <hailong.liu@...o.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.com>, Barry Song <21cnbao@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Tangquan Zheng <zhengtangquan@...o.com>, stable@...r.kernel.org,
	Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v1] mm/vmalloc: fix page mapping if
 vm_area_alloc_pages() with high order fallback to order 0

On 08/17/24 at 12:11am, Baoquan He wrote:
> On 08/16/24 at 12:13pm, Uladzislau Rezki wrote:
> > On Fri, Aug 16, 2024 at 05:12:32PM +0800, Hailong Liu wrote:
> > > On Thu, 15. Aug 22:07, Andrew Morton wrote:
> > > > On Fri, 9 Aug 2024 11:41:42 +0200 Uladzislau Rezki <urezki@...il.com> wrote:
> > > >
> > > > > > > Acked-by: Barry Song <baohua@...nel.org>
> > > > > > >
> > > > > > > because we already have a fallback here:
> > > > > > >
> > > > > > > void *__vmalloc_node_range_noprof :
> > > > > > >
> > > > > > > fail:
> > > > > > >         if (shift > PAGE_SHIFT) {
> > > > > > >                 shift = PAGE_SHIFT;
> > > > > > >                 align = real_align;
> > > > > > >                 size = real_size;
> > > > > > >                 goto again;
> > > > > > >         }
> > > > > >
> > > > > > This really deserves a comment because this is not really clear at all.
> > > > > > The code is also fragile and it would benefit from some re-org.
> > > > > >
> > > > > > Thanks for the fix.
> > > > > >
> > > > > > Acked-by: Michal Hocko <mhocko@...e.com>
> > > > > >
> > > > > I agree. This is only clear for people who know the code. A "fallback"
> > > > > to order-0 should be commented.
> > > >
> > > > It's been a week.  Could someone please propose a fixup patch to add
> > > > this comment?
> > > 
> > > Hi Andrew:
> > > 
> > > Do you mean that I need to send a v2 patch with the the comments included?
> > > 
> > It is better to post v2.
> > 
> > But before, could you please comment on:
> > 
> > in case of order-0, bulk path may easily fail and fallback to the single
> > page allocator. If an request is marked as NO_FAIL, i am talking about
> > order-0 request, your change breaks GFP_NOFAIL for !order.
> 
> In case order-0, bulk_gfp masks off __GFP_NOFAIL, but alloc_gfp doesn't.
> So alloc_gfp has __GFP_NOFAIL in fallback, it won't be failed by
> alloc_pages().

Please ignore this, I didn't update my local mail box, didn't see
Hailong's reply.