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[91.12.96.111]) by smtp.gmail.com with ESMTPSA id t21sm12887992ejr.68.2020.06.25.21.59.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 25 Jun 2020 21:59:12 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: David Hildenbrand Mime-Version: 1.0 (1.0) Subject: Re: [PATCH] mm/spase: never partially remove memmap for early section Date: Fri, 26 Jun 2020 06:59:11 +0200 Message-Id: <5CA8ECA1-2360-4AAA-954F-931404EFEB2B@redhat.com> References: <20200625223952.GA17926@L-31X9LVDL-1304.local> Cc: David Hildenbrand , Dan Williams , Michal Hocko , Andrew Morton , Oscar Salvador , Linux MM , Baoquan He , Linux Kernel Mailing List In-Reply-To: <20200625223952.GA17926@L-31X9LVDL-1304.local> To: Wei Yang X-Mailer: iPhone Mail (17F80) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Am 26.06.2020 um 00:40 schrieb Wei Yang : >=20 > =EF=BB=BFOn Thu, Jun 25, 2020 at 07:53:37AM +0200, David Hildenbrand wrote= : >>=20 >>=20 >>>> Am 25.06.2020 um 01:47 schrieb Dan Williams := >>>=20 >>> =EF=BB=BFOn Wed, Jun 24, 2020 at 3:44 PM Wei Yang >>> wrote: >>> [..] >>>>> So, you are right that there is a mismatch here, but I think the >>>>> comprehensive fix is to allow early sections to be partially >>>>> depopulated/repopulated rather than have section_activate() and >>>>> section_deacticate() special case early sections. The special casing >>>>> is problematic in retrospect as section_deactivate() can't be >>>>> maintained without understand special rules in section_activate(). >>>>=20 >>>> Hmm... This means we need to adjust pfn_valid() too, which always retur= n true >>>> for early sections. >>>=20 >>> Right, rather than carry workarounds in 3 locations, and the bug that >>> has resulted from then getting out of sync, just teach early section >>> mapping to allow for the subsection populate/depopulate. >>>=20 >>=20 >> I prefer the easy fix first - IOW what we Here here. Especially, pfn_to_o= nline_page() will need changes as well. >>=20 >=20 > Hi, David, >=20 > Which part of pfn_to_online_page() needs to be changed? pfn_valid_within()= > would call pfn_valid() to check the pfn first. This looks enough for me. Not for all configurations. For some (e.g., x86 iirc) it=E2=80=98s just a no= p.=