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Date: Thu, 30 Jul 2026 09:15:58 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Cc: Avi Weiss <thnkslprpt@gmail.com>, David Hildenbrand <david@kernel.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: <20260730091558.12e3d9029002c87c1f00b4aa@linux-foundation.org>
In-Reply-To: <amr9zoSncZguF_uu@lucifer>
References: <20260730071323.964321-1-thnkslprpt@gmail.com>
	<amr9zoSncZguF_uu@lucifer>
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On Thu, 30 Jul 2026 08:42:49 +0100 "Lorenzo Stoakes (ARM)" <ljs@kernel.org> wrote:

> 	pages_to_write_in_pmd = min_t(unsigned long,
> 		remaining_pages_total, PTRS_PER_PTE - pte_index(addr));
> 
> 	/* Allocate the PTE if necessary; takes PMD lock once only. */
> 	ret = -ENOMEM; <------------------------------ set it again?
> 	if (pte_alloc(mm, pmd))
> 		goto out;
> 
> The way this function is written is horrible in general, I hate 'preset default
> return value' as a pattern.

It used to be the preferred way because 

	ret = -ENOMEM;
	if (expr)
		goto out;

generated slightly better code than

	if (expr) {
		ret = -ENOMEM;
		goto out;
	}

Whether that is the case with current compilers I don't know.