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Wed, 07 Feb 2024 14:56:45 -0800 (PST) MIME-Version: 1.0 References: <20240206220441.38311-1-alexei.starovoitov@gmail.com> <20240206220441.38311-4-alexei.starovoitov@gmail.com> <30a722f3-dbf5-4fa3-9079-6574aae4b81d@lucifer.local> In-Reply-To: <30a722f3-dbf5-4fa3-9079-6574aae4b81d@lucifer.local> From: Alexei Starovoitov Date: Wed, 7 Feb 2024 14:56:34 -0800 Message-ID: Subject: Re: [PATCH bpf-next 03/16] mm: Expose vmap_pages_range() to the rest of the kernel. To: Lorenzo Stoakes Cc: bpf , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Kumar Kartikeya Dwivedi , Eddy Z , Tejun Heo , Barret Rhoden , Johannes Weiner , linux-mm , Kernel Team , Andrew Morton , Uladzislau Rezki , Christoph Hellwig Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 81D7940004 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: gkqs5ckgjihck5gupmc4f9ppezmpji6f X-HE-Tag: 1707346607-428410 X-HE-Meta: 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 5Xufp/Mp 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.002048, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 7, 2024 at 1:10=E2=80=AFPM Lorenzo Stoakes = wrote: > > I don't know what conventions you bpf guys follow, but it's common courte= sy > in the rest of the kernel to do a get_maintainers.pl check and figure out > who the maintainers/reviews of a part of the kernel you change are, > and include them in your mailing list. linux-mm and Johannes was cc-ed. > On Tue, Feb 06, 2024 at 02:04:28PM -0800, Alexei Starovoitov wrote: > > From: Alexei Starovoitov > > > > The next commit will introduce bpf_arena which is a sparsely populated = shared > > memory region between bpf program and user space process. > > It will function similar to vmalloc()/vm_map_ram(): > > - get_vm_area() > > - alloc_pages() > > - vmap_pages_range() > > This tells me absolutely nothing about why it is justified to expose this > internal interface. You need to put more explanation here along the lines > of 'we had no other means of achieving what we needed from vmalloc becaus= e > X, Y, Z and are absolutely convinced it poses no risk of breaking anythin= g'. Full motivation and details are in the cover letter and in the next commit = as commit log of this patch says. Everyone subscribed to linux-mm has all patches in their mailboxes. The commit log also mentioned that the next patch does pretty much what vm_map_ram() does. Any further details you're looking for? What 'risk of breaking' are you talking about? > I mean I see a lot of checks in vmap() that aren't in vmap_pages_range() > for instance. We good to expose that, not only for you but for any other > core kernel users? I could have overlooked something. What specific checks do you have in mind= ?