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Wed, 23 Sep 2020 08:04:39 +0000 (UTC) Received: from [10.36.112.54] (ovpn-112-54.ams2.redhat.com [10.36.112.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id A319C5C26B; Wed, 23 Sep 2020 08:04:36 +0000 (UTC) Subject: Re: [PATCH v4 11/23] device-dax: Kill dax_kmem_res To: Joao Martins , Dan Williams Cc: akpm@linux-foundation.org, Vishal Verma , Dave Hansen , Pavel Tatashin , peterz@infradead.org, ard.biesheuvel@linaro.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, dri-devel@lists.freedesktop.org References: <159643094279.4062302.17779410714418721328.stgit@dwillia2-desk3.amr.corp.intel.com> <159643100485.4062302.976628339798536960.stgit@dwillia2-desk3.amr.corp.intel.com> <17686fcc-202e-0982-d0de-54d5349cfb5d@oracle.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63W5Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAjwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat GmbH Message-ID: <9acc6148-72eb-7016-dba9-46fa87ded5a5@redhat.com> Date: Wed, 23 Sep 2020 10:04:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <17686fcc-202e-0982-d0de-54d5349cfb5d@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On 08.09.20 17:33, Joao Martins wrote: > [Sorry for the late response] > > On 8/21/20 11:06 AM, David Hildenbrand wrote: >> On 03.08.20 07:03, Dan Williams wrote: >>> @@ -37,109 +45,94 @@ int dev_dax_kmem_probe(struct device *dev) >>> * could be mixed in a node with faster memory, causing >>> * unavoidable performance issues. >>> */ >>> - numa_node = dev_dax->target_node; >>> if (numa_node < 0) { >>> dev_warn(dev, "rejecting DAX region with invalid node: %d\n", >>> numa_node); >>> return -EINVAL; >>> } >>> >>> - /* Hotplug starting at the beginning of the next block: */ >>> - kmem_start = ALIGN(range->start, memory_block_size_bytes()); >>> - >>> - kmem_size = range_len(range); >>> - /* Adjust the size down to compensate for moving up kmem_start: */ >>> - kmem_size -= kmem_start - range->start; >>> - /* Align the size down to cover only complete blocks: */ >>> - kmem_size &= ~(memory_block_size_bytes() - 1); >>> - kmem_end = kmem_start + kmem_size; >>> - >>> - new_res_name = kstrdup(dev_name(dev), GFP_KERNEL); >>> - if (!new_res_name) >>> + res_name = kstrdup(dev_name(dev), GFP_KERNEL); >>> + if (!res_name) >>> return -ENOMEM; >>> >>> - /* Region is permanently reserved if hotremove fails. */ >>> - new_res = request_mem_region(kmem_start, kmem_size, new_res_name); >>> - if (!new_res) { >>> - dev_warn(dev, "could not reserve region [%pa-%pa]\n", >>> - &kmem_start, &kmem_end); >>> - kfree(new_res_name); >>> + res = request_mem_region(range.start, range_len(&range), res_name); >> >> I think our range could be empty after aligning. I assume >> request_mem_region() would check that, but maybe we could report a >> better error/warning in that case. >> > dax_kmem_range() already returns a memory-block-aligned @range but > IIUC request_mem_region() isn't checking for that. Having said that > the returned @res wouldn't be different from the passed range.start. > >>> /* >>> * Ensure that future kexec'd kernels will not treat this as RAM >>> * automatically. >>> */ >>> - rc = add_memory_driver_managed(numa_node, new_res->start, >>> - resource_size(new_res), kmem_name); >>> + rc = add_memory_driver_managed(numa_node, res->start, >>> + resource_size(res), kmem_name); >>> + >>> + res->flags |= IORESOURCE_BUSY; >> >> Hm, I don't think that's correct. Any specific reason why to mark the >> not-added, unaligned parts BUSY? E.g., walk_system_ram_range() could >> suddenly stumble over it - and e.g., similarly kexec code when trying to >> find memory for placing kexec images. I think we should leave this >> !BUSY, just as it is right now. >> > Agreed. > >>> if (rc) { >>> - release_resource(new_res); >>> - kfree(new_res); >>> - kfree(new_res_name); >>> + release_mem_region(range.start, range_len(&range)); >>> + kfree(res_name); >>> return rc; >>> } >>> - dev_dax->dax_kmem_res = new_res; >>> + >>> + dev_set_drvdata(dev, res_name); >>> >>> return 0; >>> } >>> >>> #ifdef CONFIG_MEMORY_HOTREMOVE >>> -static int dev_dax_kmem_remove(struct device *dev) >>> +static void dax_kmem_release(struct dev_dax *dev_dax) >>> { >>> - struct dev_dax *dev_dax = to_dev_dax(dev); >>> - struct resource *res = dev_dax->dax_kmem_res; >>> - resource_size_t kmem_start = res->start; >>> - resource_size_t kmem_size = resource_size(res); >>> - const char *res_name = res->name; >>> int rc; >>> + struct device *dev = &dev_dax->dev; >>> + const char *res_name = dev_get_drvdata(dev); >>> + struct range range = dax_kmem_range(dev_dax); >>> >>> /* >>> * We have one shot for removing memory, if some memory blocks were not >>> * offline prior to calling this function remove_memory() will fail, and >>> * there is no way to hotremove this memory until reboot because device >>> - * unbind will succeed even if we return failure. >>> + * unbind will proceed regardless of the remove_memory result. >>> */ >>> - rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size); >>> - if (rc) { >>> - any_hotremove_failed = true; >>> - dev_err(dev, >>> - "DAX region %pR cannot be hotremoved until the next reboot\n", >>> - res); >>> - return rc; >>> + rc = remove_memory(dev_dax->target_node, range.start, range_len(&range)); >>> + if (rc == 0) { >> >> if (!rc) ? >> > Better off would be to keep the old order: > > if (rc) { > any_hotremove_failed = true; > dev_err(dev, "%#llx-%#llx cannot be hotremoved until the next reboot\n", > range.start, range.end); > return; > } > > release_mem_region(range.start, range_len(&range)); > dev_set_drvdata(dev, NULL); > kfree(res_name); > return; > > >>> + release_mem_region(range.start, range_len(&range)); >> >> remove_memory() does a release_mem_region_adjustable(). Don't you >> actually want to release the *unaligned* region you requested? >> > Isn't it what we're doing here? > (The release_mem_region_adjustable() is using the same > dax_kmem-aligned range and there's no split/adjust) > > Meaning right now (+ parent marked as !BUSY), and if I am understanding > this correctly: > > request_mem_region(range.start, range_len) > __request_region(iomem_res, range.start, range_len) -> alloc @parent > add_memory_driver_managed(parent.start, resource_size(parent)) > __request_region(parent.start, resource_size(parent)) -> alloc @child > > [...] > > remove_memory(range.start, range_len) > request_mem_region_adjustable(range.start, range_len) > __release_region(range.start, range_len) -> remove @child > > release_mem_region(range.start, range_len) > __release_region(range.start, range_len) -> doesn't remove @parent because !BUSY? > > The add/removal of this relies on !BUSY. But now I am wondering if the parent remaining > unreleased is deliberate even on CONFIG_MEMORY_HOTREMOVE=y. > > Joao > Thinking about it, if we don't set the parent resource BUSY (which is what I think is the right way of doing things), and don't want to store the parent resource pointer, we could add something like lookup_resource() - e.g., lookup_mem_resource() - , however, searching properly in the whole hierarchy (instead of only the first level), and traversing down to the last hierarchy. Then it would be as simple as remove_memory(range.start, range_len) res = lookup_mem_resource(range.start); release_resource(res); -- Thanks, David / dhildenb