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Miller" , Yunsheng Lin , Yonglong Liu , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-mm@kvack.org, netdev@vger.kernel.org Subject: Re: [RFC PATCH net-next] page_pool: Track DMA-mapped pages and unmap them when destroying the pool In-Reply-To: <2cb9c1fd-db44-4f66-9c5b-03155c6187d6@gmail.com> References: <20250308145500.14046-1-toke@redhat.com> <87cyeqml3d.fsf@toke.dk> <87tt7ziswg.fsf@toke.dk> <2cb9c1fd-db44-4f66-9c5b-03155c6187d6@gmail.com> X-Clacks-Overhead: GNU Terry Pratchett Date: Tue, 11 Mar 2025 16:49:37 +0100 Message-ID: <87frjjin3i.fsf@toke.dk> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xUpDyBKPsnsEsgCPrh4T0uHgSa-Ju9fURbMdB_SqyGY_1741708179 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 528BF1A0009 X-Stat-Signature: pbsbnxo8c3fn17813d74bffr7x554uft X-Rspamd-Server: rspam09 X-HE-Tag: 1741708182-175747 X-HE-Meta: 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 8/ndiPme 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 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: List-Subscribe: List-Unsubscribe: Pavel Begunkov writes: > On 3/11/25 13:44, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> Pavel Begunkov writes: >>=20 >>> On 3/9/25 12:42, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >>>> Mina Almasry writes: > ... >>>> No, pp_magic was also my backup plan (see the other thread). Tried >>>> actually doing that now, and while there's a bit of complication due t= o >>>> the varying definitions of POISON_POINTER_DELTA across architectures, >>>> but it seems that this can be defined at compile time. I'll send a v2 >>>> RFC with this change. >>> >>> FWIW, personally I like this one much more than an extra indirection >>> to pp. >>> >>> If we're out of space in the page, why can't we use struct page * >>> as indices into the xarray? Ala >>> >>> struct page *p =3D ...; >>> xa_store(xarray, index=3D(unsigned long)p, p); >>> >>> Indices wouldn't be nicely packed, but it's still a map. Is there >>> a problem with that I didn't consider? >>=20 >> Huh. As I just replied to Yunsheng, I was under the impression that this >> was not supported. But since you're now the second person to suggest >> this, I looked again, and it looks like I was wrong. There does indeed >> seem to be other places in the kernel that does this. > > And I just noticed there is an entire discussion my email > client didn't pull :) > > At least that's likely the easiest solution. Depends on how > complicated it is to fit the index in, but there is an option > to just go with it and continue the discussion on how to > improve it on top. Didn't seem to be too complicated, assuming no problems appear with using the middle bits of the pp_magic field. See v2 of the RFC, or here for the latest version: https://git.kernel.org/toke/c/df6248a71f85 -Toke