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[71.191.145.202]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-55ad0a231d1sm25865101cf.15.2026.11.13.12.14.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 12:14:24 -0800 (PST) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [PATCH] mm/mempolicy: ignore a bind policy whose nodes have no memory From: "Gregory Price (Meta)" To: Zi Yan Cc: "Gregory Price (Meta)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, david@kernel.org, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com In-Reply-To: References: <20261113192642.2618878-1-gourry@gourry.net> Date: Fri, 13 Nov 2026 15:14:23 -0500 Message-Id: <179460086396.482102.9206100238305098014.b4-reply@b4> X-Mailer: b4 0.17-dev On 2026-11-13 14:47 -0500, Zi Yan wrote: > On 13 Nov 2026, at 14:26, Gregory Price (Meta) wrote: > > > apply_policy_zone() assumes that policy->nodes intersects N_MEMORY, so > > it reads a bind policy with no N_HIGH_MEMORY node as movable-only. > > > > On systems with CONFIG_CPUSETS=n, nothing rebinds policies when memory > > is removed, so offlining all memory on the nodes a bind policy names > > leaves it with none. The policy is then treated as movable-only, and > > movable allocations are restricted to nodes without memory. > > > > This results in allocations failures, a VM_FAULT_OOM leak, and then > > an infinitely retrying fault that hangs the process. > > > > page allocation failure: order:0, mode:0x140dca ... nodemask=2 > > Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF > > > > Ignore a bind policy whose nodes have no memory. policy_nodemask() > > already ignores a bind policy that does not intersect the cpuset. > > This covers hugetlb's policy_mbind_nodemask() as well. > > > > If the nodes regain memory, the policy applies again. > > > > CPUSETS=n with HOTREMOVE=y is unlikely a common configuration, so this > > isn't marked for stable. > > Also no Fixes? > It wasn't quite obvious what to tag exactly. Since I don't think it's worth backporting, wasn't sure I should bother spending time on the Fixes tag. -- ~Gregory