From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pz2-f43.google.com (mail-pz2-f43.google.com [74.125.228.43]) (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 7092947534C for ; Fri, 18 Sep 2026 17:59:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.228.43 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789754378; cv=none; b=MNjbv7XG3cu1ICXMOzZoc/fv3z7a0Pd9uKeoAmdtzqnEElKE3ZfVSc+GqwD54mg1kBsjitcbBwzMMjlaXLpZ3e8mYh7WUBfWR920j72zicORrYkp5ozeh7qnSM0AQEkgloxQV5xgnbaeBK//NGlX+So+H4skbbHLaB1/gKVNYtA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789754378; c=relaxed/simple; bh=H2ewWyZoTUuSMbvTqm7kRdUUeaX6ArFU5bbm3PW2ePc=; h=Content-Type:Date:Message-Id:Cc:Subject:From:To:In-Reply-To: References:MIME-Version; b=FEInRXTDSASvgAyVR1IChI+cZgdr3rrwptBGylmNly5YgXHnVbKo5H2R7hIYG8uKbWhuv88zd+HwjcrOzu2nq6wDre6r+930Pnp9LkBNChj2Ykc0OM4jx+SqOLaRLl3oCthVwa3r8sq2WOZpj1Kwf4vHPb6ywYpZJL4yqU6D4Hk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=O+TYcg/m; arc=none smtp.client-ip=74.125.228.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="O+TYcg/m" Received: by mail-pz2-f43.google.com with SMTP id d2e1a72fcca58-86b90133ae8so826299b3a.1 for ; Fri, 18 Sep 2026 10:59:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789754377; x=1790359177; darn=vger.kernel.org; h=mime-version:content-transfer-encoding:references:in-reply-to:to :from:subject:cc:message-id:date:content-type:from:to:cc:subject :date:message-id:reply-to:content-type; bh=5pI5RH2G6KIV3wXGdA0IQ/j93krFOJLQpi1nXbIewQs=; b=O+TYcg/mNMrepe2+sZmrVbzWLLxQ03tSO8PErWeZXE4oVMv6r/gkklc5754FvU6BdH RD21sbLIqNyh8p9M8pyYOFbjhiaVypkDd0B93cNBZP4NvmlYxYgRrl+1u6X/wgntsVLq 5JLDU6dXsn6jowB7KcVax9sfA3+1arFn2nVMhJQYgld8Zc3Lhy/VJeTT7f+B+Hr87qsg t+PL4Z86xN5v/7zR3JwbIPNxWYsaPqvfy6A863tVpCB85bFlCah0chCMxh/TWsg0VSDZ QjxvLd3dwy8qkCLx2aOFolZVN9J4SxAGvstiE0/hjgxm0ewFZxtz+0SiXttMTRUvVcvA 1W2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789754377; x=1790359177; h=mime-version:content-transfer-encoding:references:in-reply-to:to :from:subject:cc:message-id:date:content-type:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=5pI5RH2G6KIV3wXGdA0IQ/j93krFOJLQpi1nXbIewQs=; b=BDnJGgKz481MjyRISYhQBkhDDg44LuugyP5Sz9NFCPdmS6qssog/sJfJdokSdLN8oL zQK2oxyRqP/enn2TVxejwYd5SzMjXIkfdmQm6NH61hy+Ka8gdesYSH9jfv4biu8DOe2u 2MFIYrEe++uoT/EVT/CwcqXZ9bfojRxgYNH1bsz6jVRtvC3x7b4FjRoQJ3ujsTCVleHn UfQrt44QKlW43VBCrpV/VhxDRrLlqQYG2oKKM41PY+4xhTEk8iAV2sbB+4GMGWl55Pm3 FOa25HzfQtPRUirxhOzLJev18nA11jvUYDjREF4Yh/KywlFcAQof65oaCHMT/Sd5yi3j tUuw== X-Forwarded-Encrypted: i=1; AKwUvByKzn7wh6FI3LxSYE7U9X3wP8Pbr2VCYErYg0ROmW9wO4qQj8Oiv/T/ZpcJtBsxI+TajDbOO6B8r3XcbVoi4m8=@vger.kernel.org X-Gm-Message-State: AFuF++lvBTyV8coRrrfJJ/iebKEtP0H3cOplrys601BcqwK9arFaXo6v fVNC9AMMoJidREacutjwMjLB8hk2I9p56dyAYmIJaOiTc/o7tzWPwhPF X-Gm-Gg: AYBFou2clELfj9BqY0pz26UIuZfOrwtVcFa4TjwU4JUAMpNvHn9YlB8t8/NdDg3WcP/ UlkYHsACsc9A8i1HSIWenHL3kSt1myfSJJw+Kzt6icoZ9aNZf6LVUVDiSzyFzyYIOyUIugUVsrS vB0BVG6zHzSk8e9urmrLd/hzOS1Dq3DadfBGXr/FvHuKvJM8buS1VuGwDSTLrXBnb3GN2jJ1V33 Tq1CVacRXIFxj3NOChliRswWcQnOrOQjq/p7C3mKm7HqsBBQTJREWAfZsHTZVG1In/lH7ZmkMxk MriwwjTRmmSD0YzbOSGjwA65nqm1wZrfd7O2R8hZS1rl2GTrzcG6NDngsvQ/2rQMbuN7O7H13oY eWbY00o2X9e350bXu5cv8+ZPhttpzgRcaaqvpniCJ+RWe1pD5wT4smLvJH+hii3LMpv3E9wJmJ6 nWzx43/EHAwbsKzmDyNBoigWI/DfLIWAT9HTVp3XMTfUPSxw5qbkb2IBqCQy/D+ld9jUqOubDqd MmA4dE2ZkjbrkOVmndBfgreTxMQ78X1/6jejnAXnsI7+tq2F1UTaJZXRC0Xc7Yr218Nq2mPuX2S k/Xb X-Received: by 2002:a05:6a20:3d06:b0:3dd:85a8:cacd with SMTP id adf61e73a8af0-3dd8c47dd66mr7132147637.36.1789754376511; Fri, 18 Sep 2026 10:59:36 -0700 (PDT) Received: from localhost ([153.61.198.254]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc5c50b0c93sm1410710a12.14.2026.09.18.10.59.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Sep 2026 10:59:36 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Fri, 18 Sep 2026 17:59:35 +0000 Message-Id: Cc: "Emil Tsalapatis" , "Daniel Borkmann" , "Andrii Nakryiko" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Martin KaFai Lau" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "Ihor Solodrai" , "Shuah Khan" , , Subject: Re: [PATCH bpf-next v8 1/3] bpf: arena: allocate the fault-in page outside the lock From: "Alexei Starovoitov" To: "Jiayuan Chen" , In-Reply-To: <20260918084123.39477-2-jiayuan.chen@linux.dev> References: <20260918084123.39477-1-jiayuan.chen@linux.dev> <20260918084123.39477-2-jiayuan.chen@linux.dev> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, Sep 18, 2026 at 04:40 PM Jiayuan Chen wrote: > @@ -489,59 +490,108 @@ static vm_fault_t arena_vm_fault(struct vm_fault *vmf) > kbase = bpf_arena_get_kern_vm_start(arena); > kaddr = kbase + (u32)(vmf->address); > > - if (raw_res_spin_lock_irqsave(&arena->spinlock, flags)) > + page = vmalloc_to_page((void *)kaddr); > + if (!page && !(arena->map.map_flags & BPF_F_SEGV_ON_FAULT)) { > + /* > + * Preallocate outside the lock so the allocation can sleep and > + * reclaim, which the non-blocking allocator under > + * arena->spinlock cannot. __GFP_RETRY_MAYFAIL: reclaim, but > + * never OOM-kill in the map's memcg, which need not be the > + * faulting task's. On failure, fallthrough: the locked > + * recheck below picks up a page a concurrent allocator may > + * have installed meanwhile, and otherwise the non-blocking > + * fallback fails and we return VM_FAULT_SIGBUS. Not > + * VM_FAULT_OOM: nothing ran the OOM killer, an d the fault path > + * would just retry it forever. > + */ I asked for one line comment. This block and the one in !new_page branch below repeat the commit log. Trim both to a sentence or two. pw-bot: cr