From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by kanga.kvack.org (Postfix) with ESMTP id E52426B000C for ; Mon, 12 Nov 2018 14:27:42 -0500 (EST) Received: by mail-qk1-f199.google.com with SMTP id k66so26043591qkf.1 for ; Mon, 12 Nov 2018 11:27:42 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id m50sor18688417qtb.61.2018.11.12.11.27.42 for (Google Transport Security); Mon, 12 Nov 2018 11:27:42 -0800 (PST) Date: Mon, 12 Nov 2018 19:27:38 +0000 From: Pavel Tatashin Subject: Re: [PATCH 3/5] mm/memory_hotplug: Check for IORESOURCE_SYSRAM in release_mem_region_adjustable Message-ID: <20181112192738.n3cbsgtbjokikvco@soleen.tm1wkky2jk1uhgkn0ivaxijq1c.bx.internal.cloudapp.net> References: <20181015153034.32203-1-osalvador@techadventures.net> <20181015153034.32203-4-osalvador@techadventures.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181015153034.32203-4-osalvador@techadventures.net> Sender: owner-linux-mm@kvack.org List-ID: To: Oscar Salvador Cc: akpm@linux-foundation.org, mhocko@suse.com, dan.j.williams@intel.com, yasu.isimatu@gmail.com, rppt@linux.vnet.ibm.com, malat@debian.org, linux-kernel@vger.kernel.org, pavel.tatashin@microsoft.com, jglisse@redhat.com, Jonathan.Cameron@huawei.com, rafael@kernel.org, david@redhat.com, dave.jiang@intel.com, linux-mm@kvack.org, alexander.h.duyck@linux.intel.com, Oscar Salvador On 18-10-15 17:30:32, Oscar Salvador wrote: > From: Oscar Salvador > > This is a preparation for the next patch. > > Currently, we only call release_mem_region_adjustable() in __remove_pages > if the zone is not ZONE_DEVICE, because resources that belong to > HMM/devm are being released by themselves with devm_release_mem_region. > > Since we do not want to touch any zone/page stuff during the removing > of the memory (but during the offlining), we do not want to check for > the zone here. > So we need another way to tell release_mem_region_adjustable() to not > realease the resource in case it belongs to HMM/devm. > > HMM/devm acquires/releases a resource through > devm_request_mem_region/devm_release_mem_region. > > These resources have the flag IORESOURCE_MEM, while resources acquired by > hot-add memory path (register_memory_resource()) contain > IORESOURCE_SYSTEM_RAM. > > So, we can check for this flag in release_mem_region_adjustable, and if > the resource does not contain such flag, we know that we are dealing with > a HMM/devm resource, so we can back off. > > Signed-off-by: Oscar Salvador > --- > kernel/resource.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/kernel/resource.c b/kernel/resource.c > index 81937830a42f..c45decd7d6af 100644 > --- a/kernel/resource.c > +++ b/kernel/resource.c > @@ -1272,6 +1272,22 @@ int release_mem_region_adjustable(struct resource *parent, > continue; > } > > + /* > + * All memory regions added from memory-hotplug path > + * have the flag IORESOURCE_SYSTEM_RAM. > + * If the resource does not have this flag, we know that > + * we are dealing with a resource coming from HMM/devm. > + * HMM/devm use another mechanism to add/release a resource. > + * This goes via devm_request_mem_region and > + * devm_release_mem_region. > + * HMM/devm take care to release their resources when they want, > + * so if we are dealing with them, let us just back off here. > + */ > + if (!(res->flags & IORESOURCE_SYSRAM)) { > + ret = 0; > + break; > + } > + > if (!(res->flags & IORESOURCE_MEM)) > break; Reviewed-by: Pavel Tatashin A couple nits, re-format above comment block to fill 80-char limit: /* * All memory regions added from memory-hotplug path have the * flag IORESOURCE_SYSTEM_RAM. If the resource does not have * this flag, we know that we are dealing with a resource coming * from HMM/devm. HMM/devm use another mechanism to add/release * a resource. This goes via devm_request_mem_region and * devm_release_mem_region. HMM/devm take care to release their * resources when they want, so if we are dealing with them, let * us just back off here. */ I would set ret = 0, at the beginning instead of -EINVAL, and change returns accordingly. Thank you, Pasha