From nobody Mon Feb 9 11:26:45 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48D3CC001B0 for ; Thu, 13 Jul 2023 14:57:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232164AbjGMO5G (ORCPT ); Thu, 13 Jul 2023 10:57:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231671AbjGMO5E (ORCPT ); Thu, 13 Jul 2023 10:57:04 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A6262735 for ; Thu, 13 Jul 2023 07:56:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689260163; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/51NS5IdbGhAF1WTe4etoP/bWkQWV6fSApbrFXQZ0Fk=; b=MWobhaLhcyFJUy2mHqAAjzdH6YBZ3caMU9yGIKHnLWufmHz61b7aW9klbl21GeDQ7qBGQQ i9ZNdDtXR2M6IOLbT3AcmJ3It6oRmFG6KQ0kAkS9/0WRbvVxq0XDV80Euflh42uUuYHfrF TdCI9JhVQQPYLmoGv9jNfPQQHJsDgU4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-669-Cnd2LY13MK-Zy4GC5ZFc9w-1; Thu, 13 Jul 2023 10:56:01 -0400 X-MC-Unique: Cnd2LY13MK-Zy4GC5ZFc9w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C7FA283FC20; Thu, 13 Jul 2023 14:56:00 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.39.192.245]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9F036F66D1; Thu, 13 Jul 2023 14:55:59 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, virtualization@lists.linux-foundation.org, David Hildenbrand , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo Subject: [PATCH v1 3/4] virtio-mem: keep retrying on offline_and_remove_memory() errors in Sub Block Mode (SBM) Date: Thu, 13 Jul 2023 16:55:50 +0200 Message-ID: <20230713145551.2824980-4-david@redhat.com> In-Reply-To: <20230713145551.2824980-1-david@redhat.com> References: <20230713145551.2824980-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" In case offline_and_remove_memory() fails in SBM, we leave a completely unplugged Linux memory block stick around until we try plugging memory again. We won't try removing that memory block again. offline_and_remove_memory() may, for example, fail if we're racing with another alloc_contig_range() user, if allocating temporary memory fails, or if some memory notifier rejected the offlining request. Let's handle that case better, by simple retrying to offline and remove such memory. Tested using CONFIG_MEMORY_NOTIFIER_ERROR_INJECT. Signed-off-by: David Hildenbrand --- drivers/virtio/virtio_mem.c | 92 +++++++++++++++++++++++++++++-------- 1 file changed, 73 insertions(+), 19 deletions(-) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 1a76ba2bc118..a5cf92e3e5af 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -168,6 +168,13 @@ struct virtio_mem { /* The number of subblocks per Linux memory block. */ uint32_t sbs_per_mb; =20 + /* + * Some of the Linux memory blocks tracked as "partially + * plugged" are completely unplugged and can be offlined + * and removed -- which previously failed. + */ + bool have_unplugged_mb; + /* Summary of all memory block states. */ unsigned long mb_count[VIRTIO_MEM_SBM_MB_COUNT]; =20 @@ -765,6 +772,34 @@ static int virtio_mem_sbm_offline_and_remove_mb(struct= virtio_mem *vm, return virtio_mem_offline_and_remove_memory(vm, addr, size); } =20 +/* + * Try (offlining and) removing memory from Linux in case all subblocks are + * unplugged. Can be called on online and offline memory blocks. + * + * May modify the state of memory blocks in virtio-mem. + */ +static int virtio_mem_sbm_try_remove_unplugged_mb(struct virtio_mem *vm, + unsigned long mb_id) +{ + int rc; + + /* + * Once all subblocks of a memory block were unplugged, offline and + * remove it. + */ + if (!virtio_mem_sbm_test_sb_unplugged(vm, mb_id, 0, vm->sbm.sbs_per_mb)) + return 0; + + /* offline_and_remove_memory() works for online and offline memory. */ + mutex_unlock(&vm->hotplug_mutex); + rc =3D virtio_mem_sbm_offline_and_remove_mb(vm, mb_id); + mutex_lock(&vm->hotplug_mutex); + if (!rc) + virtio_mem_sbm_set_mb_state(vm, mb_id, + VIRTIO_MEM_SBM_MB_UNUSED); + return rc; +} + /* * See virtio_mem_offline_and_remove_memory(): Try to offline and remove a * all Linux memory blocks covered by the big block. @@ -1988,20 +2023,10 @@ static int virtio_mem_sbm_unplug_any_sb_online(stru= ct virtio_mem *vm, } =20 unplugged: - /* - * Once all subblocks of a memory block were unplugged, offline and - * remove it. This will usually not fail, as no memory is in use - * anymore - however some other notifiers might NACK the request. - */ - if (virtio_mem_sbm_test_sb_unplugged(vm, mb_id, 0, vm->sbm.sbs_per_mb)) { - mutex_unlock(&vm->hotplug_mutex); - rc =3D virtio_mem_sbm_offline_and_remove_mb(vm, mb_id); - mutex_lock(&vm->hotplug_mutex); - if (!rc) - virtio_mem_sbm_set_mb_state(vm, mb_id, - VIRTIO_MEM_SBM_MB_UNUSED); - } - + rc =3D virtio_mem_sbm_try_remove_unplugged_mb(vm, mb_id); + if (rc) + vm->sbm.have_unplugged_mb =3D 1; + /* Ignore errors, this is not critical. We'll retry later. */ return 0; } =20 @@ -2253,12 +2278,13 @@ static int virtio_mem_unplug_request(struct virtio_= mem *vm, uint64_t diff) =20 /* * Try to unplug all blocks that couldn't be unplugged before, for example, - * because the hypervisor was busy. + * because the hypervisor was busy. Further, offline and remove any memory + * blocks where we previously failed. */ -static int virtio_mem_unplug_pending_mb(struct virtio_mem *vm) +static int virtio_mem_cleanup_pending_mb(struct virtio_mem *vm) { unsigned long id; - int rc; + int rc =3D 0; =20 if (!vm->in_sbm) { virtio_mem_bbm_for_each_bb(vm, id, @@ -2280,6 +2306,27 @@ static int virtio_mem_unplug_pending_mb(struct virti= o_mem *vm) VIRTIO_MEM_SBM_MB_UNUSED); } =20 + if (!vm->sbm.have_unplugged_mb) + return 0; + + /* + * Let's retry (offlining and) removing completely unplugged Linux + * memory blocks. + */ + vm->sbm.have_unplugged_mb =3D false; + + mutex_lock(&vm->hotplug_mutex); + virtio_mem_sbm_for_each_mb(vm, id, VIRTIO_MEM_SBM_MB_MOVABLE_PARTIAL) + rc |=3D virtio_mem_sbm_try_remove_unplugged_mb(vm, id); + virtio_mem_sbm_for_each_mb(vm, id, VIRTIO_MEM_SBM_MB_KERNEL_PARTIAL) + rc |=3D virtio_mem_sbm_try_remove_unplugged_mb(vm, id); + virtio_mem_sbm_for_each_mb(vm, id, VIRTIO_MEM_SBM_MB_OFFLINE_PARTIAL) + rc |=3D virtio_mem_sbm_try_remove_unplugged_mb(vm, id); + mutex_unlock(&vm->hotplug_mutex); + + if (rc) + vm->sbm.have_unplugged_mb =3D true; + /* Ignore errors, this is not critical. We'll retry later. */ return 0; } =20 @@ -2361,9 +2408,9 @@ static void virtio_mem_run_wq(struct work_struct *wor= k) virtio_mem_refresh_config(vm); } =20 - /* Unplug any leftovers from previous runs */ + /* Cleanup any leftovers from previous runs */ if (!rc) - rc =3D virtio_mem_unplug_pending_mb(vm); + rc =3D virtio_mem_cleanup_pending_mb(vm); =20 if (!rc && vm->requested_size !=3D vm->plugged_size) { if (vm->requested_size > vm->plugged_size) { @@ -2375,6 +2422,13 @@ static void virtio_mem_run_wq(struct work_struct *wo= rk) } } =20 + /* + * Keep retrying to offline and remove completely unplugged Linux + * memory blocks. + */ + if (!rc && vm->in_sbm && vm->sbm.have_unplugged_mb) + rc =3D -EBUSY; + switch (rc) { case 0: vm->retry_timer_ms =3D VIRTIO_MEM_RETRY_TIMER_MIN_MS; --=20 2.41.0