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Peter Anvin" , Ilias Apalodimas , linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org, Nicholas Piggin , x86@kernel.org Subject: Re: [PATCH v2 0/5] treewide: remove unreachable memblock_reserve() return value checks in early boot Message-ID: References: <20260706163753.193875-1-ekffu200098@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: cx56qxuaca8x38ueef3reb7k355pt9nz X-Rspamd-Queue-Id: C944DA0005 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783431636-821143 X-HE-Meta: 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 VfTH6OnK oOX9D5XeiTpRYh+DaNOE4TJq0TGsdf1o1IOIVfR1CNi+pa9+1+X2e8i8kcyNe3KsrBpo89JPYbkVoY4vMx0XntcoeoTQmyR1koevXlIzZRHtICHCqH42pO5Sd+6uHMHWsLvpDCz9/vEwUnkLFGbOegazWh7zG+dnqmZKIcGftbJ/ejvCEeRI7VJaZPDpv/1WEedAXFunIaI0x9LAKzIUgSX6jF/YQVMBSkZDP7HQhp5iuEoAll0vzhZqeTXOwdsX3JZhw70/aRtokUh0p3sxcAFPYhXkNZdI/mhPskkNJl71vFrj8nKBpKJpkEU2fVK7d5mRLQQBtURR76UA71O5UjErMZQebAtMNfxbz Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 07, 2026 at 10:24:09PM +0900, Sang-Heon Jeon wrote: > Hi Mike, > > On Tue, Jul 7, 2026 at 3:17 PM Mike Rapoport wrote: > > > > Hi Sang-Heon, > > > > On Tue, Jul 07, 2026 at 01:37:48AM +0900, Sang-Heon Jeon wrote: > > > memblock_reserve() can only return an error after memblock_allow_resize() > > > has been called. Before that it either succeeds or panics, never returning > > > an error. > > > > > > Before memblock_allow_resize() is called, the return value checks of > > > memblock_reserve() are unreachable and can be removed. > > > > I'd rather keep these checks. > > > > Removing them relies on internal details of memblock_reserve() implementation > > and the existing event sequence. If the code would move around relying on > > panic in memblock_reserve() may not be correct. > > > > And the few bytes and cycles the change saves do not worth the churn. > > Makes sense to me. > > But most early boot callers of memblock_reserve() don't check the > return value, so I thought we already rely on its internal behavior > anyway. So the few remaining checks just looked a bit inconsistent to > me. In reality it's very unlikely for memblock_reserve() to fail, especially after resize is allowed. And if it does fail, the system would trip on a memory error, usually sooner than later. > Would you still prefer to keep these checks? If so, I'm fine with > dropping this patch series. It's not a big deal :) Let's keep the checks as they are now. > Best Regards, > Sang-Heon Jeon -- Sincerely yours, Mike.