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Mon, 2 Mar 2020 15:43:20 +0000 (UTC) Received: from [10.36.116.114] (ovpn-116-114.ams2.redhat.com [10.36.116.114]) by smtp.corp.redhat.com (Postfix) with ESMTP id 58B9E92D45; Mon, 2 Mar 2020 15:43:11 +0000 (UTC) Subject: Re: [PATCH v2 3/7] mm/sparse.c: introduce a new function clear_subsection_map() To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, richardw.yang@linux.intel.com, osalvador@suse.de, dan.j.williams@intel.com, mhocko@suse.com, rppt@linux.ibm.com, robin.murphy@arm.com References: <20200220043316.19668-1-bhe@redhat.com> <20200220043316.19668-4-bhe@redhat.com> <20200301052028.GN24216@MiWiFi-R3L-srv> 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <1346f0c2-7b1f-6feb-5e9b-2854fd0022ba@redhat.com> Date: Mon, 2 Mar 2020 16:43:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200301052028.GN24216@MiWiFi-R3L-srv> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01.03.20 06:20, Baoquan He wrote: > On 02/28/20 at 03:36pm, David Hildenbrand wrote: >> On 20.02.20 05:33, Baoquan He wrote: >>> Wrap the codes which clear subsection map of one memory region from >>> section_deactivate() into clear_subsection_map(). >>> >>> Signed-off-by: Baoquan He >>> --- >>> mm/sparse.c | 46 ++++++++++++++++++++++++++++++++++++++-------- >>> 1 file changed, 38 insertions(+), 8 deletions(-) >>> >>> diff --git a/mm/sparse.c b/mm/sparse.c >>> index 977b47acd38d..df857ee9330c 100644 >>> --- a/mm/sparse.c >>> +++ b/mm/sparse.c >>> @@ -726,14 +726,25 @@ static void free_map_bootmem(struct page *memmap) >>> } >>> #endif /* CONFIG_SPARSEMEM_VMEMMAP */ >>> >>> -static void section_deactivate(unsigned long pfn, unsigned long nr_pages, >>> - struct vmem_altmap *altmap) >>> +/** >>> + * clear_subsection_map - Clear subsection map of one memory region >>> + * >>> + * @pfn - start pfn of the memory range >>> + * @nr_pages - number of pfns to add in the region >>> + * >>> + * This is only intended for hotplug, and clear the related subsection >>> + * map inside one section. >>> + * >>> + * Return: >>> + * * -EINVAL - Section already deactived. >>> + * * 0 - Subsection map is emptied. >>> + * * 1 - Subsection map is not empty. >>> + */ >> >> Less verbose please (in my preference: none and simplify return handling) >> >>> +static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages) >>> { >>> DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 }; >>> DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 }; >>> struct mem_section *ms = __pfn_to_section(pfn); >>> - bool section_is_early = early_section(ms); >>> - struct page *memmap = NULL; >>> unsigned long *subsection_map = ms->usage >>> ? &ms->usage->subsection_map[0] : NULL; >>> >>> @@ -744,8 +755,28 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, >>> if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION), >>> "section already deactivated (%#lx + %ld)\n", >>> pfn, nr_pages)) >>> - return; >>> + return -EINVAL; >>> + >>> + bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION); >>> >>> + if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) >>> + return 0; >>> + >> >> Can we please just have a >> >> subsection_map_empty() instead and handle that in the caller? >> (you can then always return true in the !VMEMMAP variant) > > I don't follow. Could you be more specific? or pseudo code please? > > The old code has to handle below case in which subsection_map has been > cleared. And I introduce clear_subsection_map() to encapsulate all > subsection map realted code so that !VMEMMAP won't have to see it any > more. > Something like this on top would be easier to understand IMHO diff --git a/mm/sparse.c b/mm/sparse.c index dc79b00ddaaa..be5c80e9cfee 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -726,20 +726,6 @@ static void free_map_bootmem(struct page *memmap) } #endif /* CONFIG_SPARSEMEM_VMEMMAP */ -/** - * clear_subsection_map - Clear subsection map of one memory region - * - * @pfn - start pfn of the memory range - * @nr_pages - number of pfns to add in the region - * - * This is only intended for hotplug, and clear the related subsection - * map inside one section. - * - * Return: - * * -EINVAL - Section already deactived. - * * 0 - Subsection map is emptied. - * * 1 - Subsection map is not empty. - */ static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages) { DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 }; @@ -758,11 +744,12 @@ static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages) return -EINVAL; bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION); + return 0; +} - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) - return 0; - - return 1; +static bool is_subsection_map_empty(unsigned long pfn, unsigned long nr_pages) +{ + return bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION); } static void section_deactivate(unsigned long pfn, unsigned long nr_pages, @@ -771,11 +758,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, struct mem_section *ms = __pfn_to_section(pfn); bool section_is_early = early_section(ms); struct page *memmap = NULL; - int rc; - - rc = clear_subsection_map(pfn, nr_pages); - if (IS_ERR_VALUE((unsigned long)rc)) + if (unlikely(clear_subsection_map(pfn, nr_pages))) return; /* * There are 3 cases to handle across two configurations @@ -794,7 +778,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, * * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified */ - if (!rc) { + if (is_subsection_map_empty(pfn, nr_pages)) { unsigned long section_nr = pfn_to_section_nr(pfn); /* @@ -816,7 +800,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, else depopulate_section_memmap(pfn, nr_pages, altmap); - if (!rc) + if (is_subsection_map_empty(pfn, nr_pages)) ms->section_mem_map = (unsigned long)NULL; } -- Thanks, David / dhildenb