From patchwork Fri Aug 21 10:34:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 11728829 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BD4FA16B1 for ; Fri, 21 Aug 2020 10:35:22 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 979B5207DA for ; Fri, 21 Aug 2020 10:35:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UwfRSjv+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 979B5207DA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k94Nw-0000Y8-Gi; Fri, 21 Aug 2020 10:35:00 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k94Nv-0000Xn-1a for xen-devel@lists.xenproject.org; Fri, 21 Aug 2020 10:34:59 +0000 X-Inumbo-ID: b8054a08-e193-454a-9e84-8032e221f063 Received: from us-smtp-delivery-1.mimecast.com (unknown [207.211.31.81]) by us1-rack-iad1.inumbo.com (Halon) with ESMTP id b8054a08-e193-454a-9e84-8032e221f063; Fri, 21 Aug 2020 10:34:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598006091; 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=XJmXFP26TlaoILesjgfmIBQIbNPk9EKlqFijZvcbNh0=; b=UwfRSjv+lN1AWLxzo1bC0dZJb9o6BtxA8Os0rqZCPbgnn06rOeNMvrktmgYt7LukaADDue E2S1aN4bKFeOMC8bRWUzRoW0gWvlv0dUIyPO8ZJgtEeUrsr2b+GTAl5esUv6BnfAl2Sbyk Yu9QJioER3grpS41DIwM2mWWRT4qorI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-229-6z0QkybENJy6Io-WetcOng-1; Fri, 21 Aug 2020 06:34:49 -0400 X-MC-Unique: 6z0QkybENJy6Io-WetcOng-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A6DAF640CA; Fri, 21 Aug 2020 10:34:47 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-87.ams2.redhat.com [10.36.114.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id CDF5460BF1; Fri, 21 Aug 2020 10:34:44 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org, David Hildenbrand , Andrew Morton , Michal Hocko , Dan Williams , Jason Gunthorpe , Kees Cook , Ard Biesheuvel , Pankaj Gupta , Baoquan He , Wei Yang Subject: [PATCH v1 1/5] kernel/resource: make release_mem_region_adjustable() never fail Date: Fri, 21 Aug 2020 12:34:27 +0200 Message-Id: <20200821103431.13481-2-david@redhat.com> In-Reply-To: <20200821103431.13481-1-david@redhat.com> References: <20200821103431.13481-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Let's make sure splitting a resource on memory hotunplug will never fail. This will become more relevant once we merge selected system ram resources - then, we'll trigger that case more frequently on memory hotunplug. In general, this function is already unlikely to fail. When we remove memory, we free up quite a lot of metadata (memmap, page tables, memory block device, etc.). The only way it could really fail currently is when injecting allocation errors. All other error cases inside release_mem_region_adjustable() seem to be sanity checks if the function would be abused in different context - let's add WARN_ON_ONCE(). Cc: Andrew Morton Cc: Michal Hocko Cc: Dan Williams Cc: Jason Gunthorpe Cc: Kees Cook Cc: Ard Biesheuvel Cc: Pankaj Gupta Cc: Baoquan He Cc: Wei Yang Signed-off-by: David Hildenbrand --- include/linux/ioport.h | 4 ++-- kernel/resource.c | 49 ++++++++++++++++++++++++------------------ mm/memory_hotplug.c | 22 +------------------ 3 files changed, 31 insertions(+), 44 deletions(-) diff --git a/include/linux/ioport.h b/include/linux/ioport.h index 6c2b06fe8beb7..52a91f5fa1a36 100644 --- a/include/linux/ioport.h +++ b/include/linux/ioport.h @@ -248,8 +248,8 @@ extern struct resource * __request_region(struct resource *, extern void __release_region(struct resource *, resource_size_t, resource_size_t); #ifdef CONFIG_MEMORY_HOTREMOVE -extern int release_mem_region_adjustable(struct resource *, resource_size_t, - resource_size_t); +extern void release_mem_region_adjustable(struct resource *, resource_size_t, + resource_size_t); #endif /* Wrappers for managed devices */ diff --git a/kernel/resource.c b/kernel/resource.c index 841737bbda9e5..1dcef5d53d76e 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1255,21 +1255,28 @@ EXPORT_SYMBOL(__release_region); * assumes that all children remain in the lower address entry for * simplicity. Enhance this logic when necessary. */ -int release_mem_region_adjustable(struct resource *parent, - resource_size_t start, resource_size_t size) +void release_mem_region_adjustable(struct resource *parent, + resource_size_t start, resource_size_t size) { + struct resource *new_res = NULL; + bool alloc_nofail = false; struct resource **p; struct resource *res; - struct resource *new_res; resource_size_t end; - int ret = -EINVAL; end = start + size - 1; - if ((start < parent->start) || (end > parent->end)) - return ret; + if (WARN_ON_ONCE((start < parent->start) || (end > parent->end))) + return; - /* The alloc_resource() result gets checked later */ - new_res = alloc_resource(GFP_KERNEL); + /* + * We free up quite a lot of memory on memory hotunplug (esp., memap), + * just before releasing the region. This is highly unlikely to + * fail - let's play save and make it never fail as the caller cannot + * perform any error handling (e.g., trying to re-add memory will fail + * similarly). + */ +retry: + new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0); p = &parent->child; write_lock(&resource_lock); @@ -1295,7 +1302,6 @@ int release_mem_region_adjustable(struct resource *parent, * so if we are dealing with them, let us just back off here. */ if (!(res->flags & IORESOURCE_SYSRAM)) { - ret = 0; break; } @@ -1312,20 +1318,23 @@ int release_mem_region_adjustable(struct resource *parent, /* free the whole entry */ *p = res->sibling; free_resource(res); - ret = 0; } else if (res->start == start && res->end != end) { /* adjust the start */ - ret = __adjust_resource(res, end + 1, - res->end - end); + WARN_ON_ONCE(__adjust_resource(res, end + 1, + res->end - end)); } else if (res->start != start && res->end == end) { /* adjust the end */ - ret = __adjust_resource(res, res->start, - start - res->start); + WARN_ON_ONCE(__adjust_resource(res, res->start, + start - res->start)); } else { - /* split into two entries */ + /* split into two entries - we need a new resource */ if (!new_res) { - ret = -ENOMEM; - break; + new_res = alloc_resource(GFP_ATOMIC); + if (!new_res) { + alloc_nofail = true; + write_unlock(&resource_lock); + goto retry; + } } new_res->name = res->name; new_res->start = end + 1; @@ -1336,9 +1345,8 @@ int release_mem_region_adjustable(struct resource *parent, new_res->sibling = res->sibling; new_res->child = NULL; - ret = __adjust_resource(res, res->start, - start - res->start); - if (ret) + if (WARN_ON_ONCE(__adjust_resource(res, res->start, + start - res->start))) break; res->sibling = new_res; new_res = NULL; @@ -1349,7 +1357,6 @@ int release_mem_region_adjustable(struct resource *parent, write_unlock(&resource_lock); free_resource(new_res); - return ret; } #endif /* CONFIG_MEMORY_HOTREMOVE */ diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 35d56cbd3e45b..f77fd1810e9f5 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1700,26 +1700,6 @@ void try_offline_node(int nid) } EXPORT_SYMBOL(try_offline_node); -static void __release_memory_resource(resource_size_t start, - resource_size_t size) -{ - int ret; - - /* - * When removing memory in the same granularity as it was added, - * this function never fails. It might only fail if resources - * have to be adjusted or split. We'll ignore the error, as - * removing of memory cannot fail. - */ - ret = release_mem_region_adjustable(&iomem_resource, start, size); - if (ret) { - resource_size_t endres = start + size - 1; - - pr_warn("Unable to release resource <%pa-%pa> (%d)\n", - &start, &endres, ret); - } -} - static int __ref try_remove_memory(int nid, u64 start, u64 size) { int rc = 0; @@ -1753,7 +1733,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) memblock_remove(start, size); } - __release_memory_resource(start, size); + release_mem_region_adjustable(&iomem_resource, start, size); try_offline_node(nid);