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AJvYcCX4gcY5hfoQfHVaCrIIFb0mYMlIHxJhQy0Vl3x89LeHMHT3+ZORRYUY2HSTdAKaK3FTEpZLpKSssg==@kvack.org X-Gm-Message-State: AOJu0Yx+oJxs4UED8W0CnrUxZJmSRjG+FSfxIVaOBAqHbN/u0KUsUVB/ 50scnNCqxXLhZRB3zPrA0VJm8/CIdT0qjvZxdy7uay+q1Bph5O158qTqyGCwCznW6uNmMrE4cCn CMdusoDNECtO3PTrdV9XuqCA9zoQ= X-Gm-Gg: ASbGncvY20isV14MQ6EFqohrnm0MjaM1gEErADf+2LXdrSap/Ro84dMJOp7v4/d9HIK RG+JGtTmOsSbH5HL1WkfZwTRvJARyEElCBm2Qg/jeo514BttgochXRHsyiZ/gwg+YHQxeRYJYn7 YmyiJNWPZ1ksJ74HvXDg== X-Google-Smtp-Source: AGHT+IGOb6vxlLhCXj3f0QNMkNMirtLON3mv0I3V7/RpuR3QBVza6e72NbwXufk1OxktCL3DsOr51N7We/tuyEmJXjM= X-Received: by 2002:a05:600c:468e:b0:436:5165:f1ec with SMTP id 5b1f17b1804b1-4389143145bmr300411335e9.30.1737735570033; Fri, 24 Jan 2025 08:19:30 -0800 (PST) MIME-Version: 1.0 References: <20250124035655.78899-1-alexei.starovoitov@gmail.com> In-Reply-To: From: Alexei Starovoitov Date: Fri, 24 Jan 2025 08:19:19 -0800 X-Gm-Features: AWEUYZmIlUPeQ03O6WtaTxXnXJkoadEdcYJvYlAh1Eej_BfMfLgZY0nrYIf9WPs Message-ID: Subject: Re: [PATCH bpf-next v6 0/6] bpf, mm: Introduce try_alloc_pages() To: Vlastimil Babka Cc: Matthew Wilcox , bpf , Andrii Nakryiko , Kumar Kartikeya Dwivedi , Andrew Morton , Peter Zijlstra , Sebastian Sewior , Steven Rostedt , Hou Tao , Johannes Weiner , Shakeel Butt , Michal Hocko , Thomas Gleixner , Jann Horn , Tejun Heo , linux-mm , Kernel Team , Marco Elver , Andrey Konovalov , Oscar Salvador Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: DCC3CA001F X-Stat-Signature: 95fbzhdrr95hu3xy7fc1jpxkbme6sxqr X-HE-Tag: 1737735571-118636 X-HE-Meta: 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 psl09vC/ Rg/sZNe5oVyHqTUfqywkj0yHncIxJD668lAdxMPdfn4bh3UEfZnRvgLFUdErNPMv/fJAvFUo89ksM+77aVJ5fJ+Q0DLFWEIKXe5SC0qvVgEoFmaInfirO9y1bJK+Nnd+FO7STZopGX6nQwEM148N7RGB3LD2EOKBlAMUE3aiE7f3jnuhbERHv8cm+eXBOr0fmPYGCdspixik8v8gy70XA+zz9+z6UVAHJo6DD0qZCprUgA/mCR4M/akQ2K2vKL4a4ulIoXGJyiPeN7cvapRblf4hlp2RoRIrmPpR7DI9l9hU7iz8zn404dTdnrhEOvL/d/Bh3Z0phjKvXbZou2JgXWGs2GG6ac4IZ8BU6aKccjx6bsJ6nmBiEnaU371KqU+M8TUt4fUt6+t8jIDA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, 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 Fri, Jan 24, 2025 at 6:19=E2=80=AFAM Vlastimil Babka wr= ote: > > On 1/24/25 15:16, Matthew Wilcox wrote: > > On Thu, Jan 23, 2025 at 07:56:49PM -0800, Alexei Starovoitov wrote: > >> - Considered using __GFP_COMP in try_alloc_pages to simplify > >> free_pages_nolock a bit, but then decided to make it work > >> for all types of pages, since free_pages_nolock() is used by > >> stackdepot and currently it's using non-compound order 2. > >> I felt it's best to leave it as-is and make free_pages_nolock() > >> support all pages. > > > > We're trying to eliminate non-use of __GFP_COMP. Because people don't > > use __GFP_COMP, there's a security check that we can't turn on. Would > > you reconsider this change you made? > > This means changing stackdepot to use __GFP_COMP. Which would be a good > thing on its own. But if you consider if off-topic to your series, I can > look at it. Ohh. I wasn't aware of that. I can certainly add __GFP_COMP to try_alloc_pages() and will check stackdepot too. I spotted this line: VM_BUG_ON_PAGE(compound && compound_order(page) !=3D order, page); that line alone was a good enough reason to use __GFP_COMP, but since it's debug only I could only guess where the future lies. Should it be something like: if (WARN_ON(compound && compound_order(page) !=3D order)) order =3D compound_order(page); since proceeding with the wrong order is certain to crash. ?