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: <20240815220709.47f66f200fd0a072777cc348@linux-foundation.org>
Date: Thu, 15 Aug 2024 22:07:09 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Uladzislau Rezki <urezki@...il.com>
Cc: Michal Hocko <mhocko@...e.com>, Barry Song <21cnbao@...il.com>, Hailong
 Liu <hailong.liu@...o.com>, Christoph Hellwig <hch@...radead.org>,
 Vlastimil Babka <vbabka@...e.cz>, Tangquan Zheng <zhengtangquan@...o.com>,
 stable@...r.kernel.org, Baoquan He <bhe@...hat.com>, 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 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?