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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90c5f2b2b38sm67816356d6.43.2026.08.21.10.47.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2026 10:47:12 -0700 (PDT) Date: Fri, 21 Aug 2026 13:47:10 -0400 From: Gregory Price To: Andrew Morton Cc: Eric Dumazet , linux-kernel , syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com, David Hildenbrand , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , linux-mm@kvack.org Subject: Re: [PATCH] mm/mempolicy: Fix sleeping allocation in alloc_pages_bulk_weighted_interleave() Message-ID: References: <20260821170407.3721004-1-edumazet@google.com> <20260821104043.f692421fec915c0c5bc1fbe6@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260821104043.f692421fec915c0c5bc1fbe6@linux-foundation.org> X-Rspamd-Queue-Id: 9EE7A1C0011 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: 13o1h661q5qe99m1yrd8xjjwy4g63711 X-HE-Tag: 1787334433-741931 X-HE-Meta: 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 aO2MIA7N 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 21, 2026 at 10:40:43AM -0700, Andrew Morton wrote: > On Fri, 21 Aug 2026 17:04:07 +0000 Eric Dumazet wrote: > > I wonder if we *really* need the local copy of state->iw_table. > Perhaps with appropriate care we can directly use state->iw_table in > here. > > How much would it hurt to expand the rcu_read_lock() coverage? > > A local array of MAX_NUMNODES bytes isn't attractive - 1k of stack. > > A spinlock-protected static array would work, if super-rare slowpath. > I would need to go back through the original thread when i authored this, but I think this is possible. I will add it to my backlog to investigate. Weight updates should be *extraordinarily* rare, unless someone is doing dynamic runtime twiddling of the sysfs values and thinks that's somehow a good idea (or expecting them to be timely). ~Gregory