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Date: Thu, 30 Jul 2026 09:36:25 +0100
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Avi Weiss <thnkslprpt@gmail.com>, 
	Andrew Morton <akpm@linux-foundation.org>, "Liam R. Howlett" <liam@infradead.org>, 
	Vlastimil Babka <vbabka@kernel.org>, Mike Rapoport <rppt@kernel.org>, 
	Suren Baghdasaryan <surenb@google.com>, Michal Hocko <mhocko@suse.com>, 
	Soheil Hassas Yeganeh <soheil@google.com>, Arjun Roy <arjunroy@google.com>, 
	Eric Dumazet <edumazet@google.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: return -ENOMEM for page-table allocation failure in
 insert_pages()
Message-ID: <amsM9I3at8ZE4A77@lucifer>
References: <20260730071323.964321-1-thnkslprpt@gmail.com>
 <amr9zoSncZguF_uu@lucifer>
 <2a84e37c-407b-437c-a908-56526ce86322@kernel.org>
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In-Reply-To: <2a84e37c-407b-437c-a908-56526ce86322@kernel.org>

On Thu, Jul 30, 2026 at 10:27:20AM +0200, David Hildenbrand (Arm) wrote:
> On 7/30/26 09:42, Lorenzo Stoakes (ARM) wrote:
> > On Thu, Jul 30, 2026 at 10:13:23AM +0300, Avi Weiss wrote:
> >> walk_to_pmd() returns NULL only when p4d_alloc(), pud_alloc(), or
> >> pmd_alloc() fails. These are page-table allocation failures, but
> >> insert_pages() currently reports them as -EFAULT.
> >>
> >> Return -ENOMEM instead, consistent with the subsequent pte_alloc()
> >> failure and with the single-page insert_page() path, which reports
> >> failure of the same page-table allocation chain as -ENOMEM.
> >>
> >> Address and range validation failures in vm_insert_pages() continue to
> >> return -EFAULT. Keep the later -EFAULT return for
> >> pte_offset_map_lock(), which is not an allocation failure.
> >>
> >> Fixes: 8cd3984d81d5 ("mm/memory.c: add vm_insert_pages()")
> >
> > Hmm :)
> >
> > This isn't really a fix. Anybody relying on this returning -ENOMEM
> > vs. -EFAULT here is in a state of sin anyway (unless you can point to
> > specific users who are broken).
>
> Agreed, I am missing the problem here?

Seems just a cleanup, I gave Avi some ideas ;) this function could do with
it.

>
> --
> Cheers,
>
> David

Cheers, Lorenzo