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charset="UTF-8" Content-Transfer-Encoding: 7bit Importance: Medium User-Agent: Zoho Mail X-Mailer: Zoho Mail ARC-Authentication-Results: i=2; imf04.hostedemail.com; dkim=pass header.d=linux.beauty header.s=zmail header.b=V5rJcwOx; arc=pass ("zohomail.com:s=zohoarc:i=1"); dmarc=none; spf=pass (imf04.hostedemail.com: domain of me@linux.beauty designates 136.143.188.14 as permitted sender) smtp.mailfrom=me@linux.beauty ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657599828; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=AYZhl4Tgx5eXsw054d7yEPiQv66vkg0JPurDrzFEdv0=; b=zezH5hsjaTD8RuXXz57gjPOB6WrArg71E5aSEQDO+8RwUdkB6WzJLNPc+qzcoKASplUIQI zYuNfR686dn/K+Ae7/F32EC2+VBaMhanlBJ5fBev4a6dMMEuecWU/E7EF9uafbPe4MBWhn ks2CWbUgJrd483yh45m9/5IEeeSmlZQ= ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1657599828; a=rsa-sha256; cv=pass; b=l3toIbmYy92kasgOTGCRX9200CwggSm0CthUJPhrF8Orx/u55VR+BwhVwurXaS15pnbObp NGTRkK1S7LES/EIWdwCTgdILzgJTHhBicr4g+iJ8iWrK0Df1XQ7vGBQmewnTNkCuI6dkAg vsn7kys4u4wg1lcLiBgmxUqDaP9jnhE= Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=linux.beauty header.s=zmail header.b=V5rJcwOx; arc=pass ("zohomail.com:s=zohoarc:i=1"); dmarc=none; spf=pass (imf04.hostedemail.com: domain of me@linux.beauty designates 136.143.188.14 as permitted sender) smtp.mailfrom=me@linux.beauty X-Rspam-User: X-Rspamd-Server: rspam08 X-Stat-Signature: 9i77myjtazsdconsa6ef6c43us6zmmju X-Rspamd-Queue-Id: 9FC3440027 X-HE-Tag: 1657599827-385676 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi David, ---- On Mon, 11 Jul 2022 22:53:36 +0800 David Hildenbrand wrote --- > On 11.07.22 14:24, Li Chen wrote: > > From: Li Chen > > > > When mhp use sparse_add_section, don't check no-map region, > > so that to allow no-map reserved memory to get struct page > > support. > > > > Signed-off-by: Li Chen > > Change-Id: I0d2673cec1b66adf695251037a00c240976b226f > > --- > > mm/sparse.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/mm/sparse.c b/mm/sparse.c > > index 120bc8ea5293..a29cd1e7014f 100644 > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -690,7 +690,9 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages) > > > > if (bitmap_empty(map, SUBSECTIONS_PER_SECTION)) > > rc = -EINVAL; > > - else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION)) > > + else if (memblock_is_map_memory(PFN_PHYS(pfn)) && > > + bitmap_intersects(map, subsection_map, > > + SUBSECTIONS_PER_SECTION)) > > rc = -EEXIST; > > else > > bitmap_or(subsection_map, map, subsection_map, > > I'm not sure I follow completely what you are trying to achieve. But if > you have to add memblock hacks into mm/sparse.c you're most probably > doing something wrong. > > Please explain why that change is necessary, and why it is safe. In the current sparse memory model, free_area_init will insert all memblock.memory into subsection_map and no-map rmem is also a memblock.memory. So, without this change, fill_subsection_map will return -EEXIST. I would say it's not a good idea to insert no-map memblock into subsection_map, and I have no idea why sparse do this. So, I simply skip no-map region here. As for safety: 1. The caller of fill_subsection_map are mhp and *_memremap_pages functions, no-map regions are not related to them, so existing codes won't be broken. 2. This change doesn't change memblock and subsection_map. > > If the subsection map already spans memory (iow, subsection map is set) > you intend to add, then something already added memory in that range? No matter with or without this patch, fill_subsection_map will always return -EEXIST for mapped memory, so that's not a problem. The key point here is I allowed no-map region to pass the check and didn't change anything to the mapped region. Regards, Li