From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f48.google.com (mail-qv1-f48.google.com [209.85.219.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7722B42B31D for ; Mon, 20 Jul 2026 19:34:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784576102; cv=none; b=GI2T90MN0JKcnGkVsAnYU/5fN8F4GtJshewBCeMeL3kIRL53co7xB54gmDk2j9swPGhEwJwHd5nXHNYtfwEKaTdUxDa/s6UR/NLEpRzpmVWuUI4Kk4jEaAW/Wmnpo89q55rhZbVfTIvrY72K0s7R7/rLUXRHEnUjUHUr+keugK4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784576102; c=relaxed/simple; bh=5WsZz3rVrHU17snClfl3M7UsKRdvN7wn8MZmoue9j4k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p087mQfJ+ee6g8COoeCjjLBLURqWyV0g6TW/sowa0pyVjrH0gNZZ/+HYARsRSkLGsR1yQnAkCPm8Ot7Qz6d9WHqC1LslhJk289e3KbiiMlUUtSlR5FgsSVHaWR4oq+9/Eb6F3lFTnJ2D8s67eCT5ScHKfLde3htOHLwZM1y8/xI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net; spf=pass smtp.mailfrom=gourry.net; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b=AeO2JDVY; arc=none smtp.client-ip=209.85.219.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gourry.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b="AeO2JDVY" Received: by mail-qv1-f48.google.com with SMTP id 6a1803df08f44-9061a795d76so75443726d6.3 for ; Mon, 20 Jul 2026 12:34:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gourry.net; s=google; t=1784576097; x=1785180897; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=xdEOlYqIeVdUG1DfkuvgY4asc0OjHWyQnI3tw1EXx60=; b=AeO2JDVYr4O4Zalcb0OS5SE9Jc10O2vFAgaj9xZdut8hoHmRchSeoKM0BvhpKROxAj TpuEQQHgBvlffX0b8VIu1nV8QGREocf9JjP9UxFZ9eQXVahhg1tRrUD9A4iLJnjqnU/D XIPoxcFJZpI2KVfzaHdaKMiYwn6HUcDzRSXafy0wt6fsDi7jgUlsm4Z+YkBdBlbXgULG RMbHG9yXaXWjXzjsV6CaTm5w4lwraNEUyE/0uyFHlQ3BQoNARJguOH8jZENaA3p2vTJw Yz9e0Q/xakbbN00AJ15b+UP3MeSow5DU3WquVLj2BDWd+eB4x1EcbXJLqt210bh7OWze Ik5g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784576097; x=1785180897; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=xdEOlYqIeVdUG1DfkuvgY4asc0OjHWyQnI3tw1EXx60=; b=WOfu/0L3qhRCDGlxWlUqKjFi/GXZPNDl7+7QxATZ160zmJW7g5bG5AvoFVozYzz/BC 9PsTaITf9AQgMCvuDWXVcWEgNgEV69Cjty9P/K8FKWwpd7D0EyqlNpyD2n9wPniHJiAg EieE+aX8AnpZX72M88FNB+adgkwLl7YtTqq3BiGBUUjQ+fsRnRIBEiGcyySYOd5IL+oo BFB3MMDo8c2jlPX0pRAzLKu2oXhgdGFwW/T4y6o+2SYJ9E5ZBKwrU2vuKY/u91XMQ8cK Uzi8PeLdf1tkLID8u1EJeR6F+IORXeFPTxolrQN2Os7/Kwrpo8Z5O0bwFyh4B3BdmxQP zECw== X-Forwarded-Encrypted: i=1; AHgh+Rpq3BHfnDO92J7CA+4bPL3h6pSfT2Oeuo1r0anx5ZwagzzMkibx5kJTH/HERzQWfcO+ct8tp/0UjnyAAds=@vger.kernel.org X-Gm-Message-State: AOJu0Yy0p4R+jRP+1nvphjC+cJtw45kvG7+I5E6RGsrTxtEcjgO7veWM vTLkq+dGQobKosiD+JonGgFoDPmuS2shPDFbOKmhcnYpA125kJSQbDwIk95FE0TuaIY= X-Gm-Gg: AfdE7clYajf7c5xtegKEBqDj429ALm91mcmJemq6//lQmpDv3nwBDZrIHsBPvMFvjSh 8jFgqg0w0hXOcLixBr/gFm7K5H/OPyTHf9U2hw2ks1b5dk++7IcHu1c0Hk2hlAlB+rwyh8zaqp7 qIAPszPzi8fD1JH50tRy49At5RXjaptNywLS2Q67znPEVCIOwo6D21zMU/X49NKcHo49axSv2l3 SUq1m0TjaxnBBiMOWGh2LCVnnhTaip+hE2zXLqVRM9QcwG8q4fXrWFRcERrh0UvGP8+sKr1T4yc T/dfTrLj+AtHRbPjjZqR5PrpnStRZEEZbRGTKnBahc2cEu5pqqXr8IA5C6H2dXWV+9b/P/i+Wsz PFQygt7roeVOWXnT8G91enL+QryDQOyACAD1ivLjBl8v/x8nBFscZ1VpcC9bHoBLEpok9O+obTj gYGl9X+BALAabPGlKlU46UXkGGQVhCm1sPsUBwT63xk17N21vdXJiKDzwXz8sLqc4= X-Received: by 2002:a05:620a:a2c5:20b0:92f:196:209c with SMTP id af79cd13be357-930b41f9aa3mr1179416785a.71.1784576096734; Mon, 20 Jul 2026 12:34:56 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F.lan (pool-173-79-60-52.washdc.fios.verizon.net. [173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-930b545e47bsm957792285a.35.2026.07.20.12.34.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jul 2026 12:34:56 -0700 (PDT) From: Gregory Price To: linux-mm@kvack.org Cc: Zhigang.Luo@amd.com, arun.george@samsung.com, balbirs@nvidia.com, brendan.jackman@linux.dev, yuzenghui@huawei.com, apopple@nvidia.com, alucerop@amd.com, matthew.brost@intel.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, alison.schofield@intel.com, osandov@osandov.com, jannh@google.com, pfalcato@suse.de, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, pbonzini@redhat.com, osalvador@suse.de, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, longman@redhat.com, ridong.chen@linux.dev, tj@kernel.org, mkoutny@suse.com, sj@kernel.org, jgg@ziepe.ca, jhubbard@nvidia.com, peterx@redhat.com, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, lance.yang@linux.dev, usama.arif@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, driver-core@lists.linux.dev, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-debuggers@vger.kernel.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, cgroups@vger.kernel.org, damon@lists.linux.dev, linux-kselftest@vger.kernel.org, kernel-team@meta.com Subject: [PATCH v5 07/36] mm/memory_hotplug: disallow migration-driven private node hotunplug Date: Mon, 20 Jul 2026 15:34:01 -0400 Message-ID: <20260720193431.3841992-8-gourry@gourry.net> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260720193431.3841992-1-gourry@gourry.net> References: <20260720193431.3841992-1-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit By default, device-backed private node memory may not be safe to migrate without coordination. Do not attempt to hotunplug private node memory, instead fail the hotunplug attempt, and require the owner to drain the folios safely before allowing hotunplug to proceed. Unlike transient / longterm pins causing failures, this is not a transient condition - so we can break out of the hotunplug attempt entirely instead of spinning forever on a failed migration attempt. Signed-off-by: Gregory Price --- mm/memory_hotplug.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 226ab9cb078ad..2b9c0830821e6 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -34,6 +34,7 @@ #include #include #include +#include #include #include @@ -1843,11 +1844,12 @@ static int scan_movable_pages(unsigned long start, unsigned long end, return 0; } -static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) +static int do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) { struct folio *folio; unsigned long pfn; LIST_HEAD(source); + int err = 0; static DEFINE_RATELIMIT_STATE(migrate_rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST); @@ -1884,6 +1886,15 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) goto put_folio; } + /* Private node folios cannot migrate, fail outright */ + if (folio_is_private_node(folio)) { + pr_info_ratelimited("memory offline refused: node %d pfn %lx\n", + folio_nid(folio), pfn); + folio_put(folio); + err = -EBUSY; + break; + } + if (!isolate_folio_to_list(folio, &source)) { if (__ratelimit(&migrate_rs)) { pr_warn("failed to isolate pfn %lx\n", @@ -1931,6 +1942,7 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) putback_movable_pages(&source); } } + return err; } static int __init cmdline_parse_movable_node(char *p) @@ -2067,10 +2079,11 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages, ret = scan_movable_pages(pfn, end_pfn, &pfn); if (!ret) { /* - * TODO: fatal migration failures should bail - * out + * A fatal migration failure (e.g. a folio on a + * non-migratable private node) bails out; transient + * failures leave ret zero and are retried below. */ - do_migrate_range(pfn, end_pfn); + ret = do_migrate_range(pfn, end_pfn); } } while (!ret); -- 2.53.0-Meta