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AJvYcCW0gPgaNYQGSv8eF76IaPTJmbQhE9QNuVAH/DRYyu8vCJ3kCtEuRM58TC0dZEuutKJnkAArQ+sVtA==@kvack.org X-Gm-Message-State: AOJu0Yy2NGg64XLgFOdl3HM75jSl4UhZw59gIJIUSDme4DKSJjaH1S5n IJIFcOPAEWf/l6s8D2eVbWP9vYmA+2PpU4PLqfKLLFrfBt7lFU4fpyyXoBjm4TPYTpXtnj3mXPQ 3gTHPOX25r4stQ5OlZ4ZC/wFk3rWGbOY= X-Gm-Gg: ASbGncuNj9Ixyt3Jr0QQWlBsTta+X0CGHxEISxrsWJAEZkIFcjBpdRPg389Zamw6+NI 31jzqLP9ki9NUV5LKHOn1ODDxztIy0MMZtLObOmYOknIYf+IpuPKNgNP3Iq+vUf7hVCmx48xQ9x gPDaIbWQfK+DYXZOP3vUc8RDALGyBr3y1E9sZ2Zz32GZjl8R1j0yg/PINw4hrKW2lM3Z8jsxtT+ s9Y0vw6DKH7x/m9I4vOMiMXv3CJg5a69/mYhBIWAuyzxI8Ihj8BcvrbbxACceR60x7jZVuld+DL 4UCxo7LH5r+H847BVw== X-Google-Smtp-Source: AGHT+IGTMzuv/ArJ+OYA4q54z3AmWM67z6gdganGyzk1cdUdXR07L641GaC7I+IwWt6JzcrPAq7tGRPMfDWEY1QXS5M= X-Received: by 2002:a05:6000:26c2:b0:427:880:9538 with SMTP id ffacd0b85a97d-429aefbde03mr708524f8f.45.1761701583059; Tue, 28 Oct 2025 18:33:03 -0700 (PDT) MIME-Version: 1.0 References: <20251026100159.6103-1-laoar.shao@gmail.com> <20251026100159.6103-7-laoar.shao@gmail.com> In-Reply-To: <20251026100159.6103-7-laoar.shao@gmail.com> From: Alexei Starovoitov Date: Tue, 28 Oct 2025 18:32:51 -0700 X-Gm-Features: AWmQ_bntzSgbNvji5U8WdqIphFhfm5XUNy_QTFtw53IwUs3LIlTTv2I1GT8Ge5E Message-ID: Subject: Re: [PATCH v12 mm-new 06/10] mm: bpf-thp: add support for global mode To: Yafang Shao Cc: Andrew Morton , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , David Hildenbrand , Lorenzo Stoakes , Martin KaFai Lau , Eduard , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Zi Yan , Liam Howlett , npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, Johannes Weiner , usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, Matthew Wilcox , Amery Hung , David Rientjes , Jonathan Corbet , Barry Song <21cnbao@gmail.com>, Shakeel Butt , Tejun Heo , lance.yang@linux.dev, Randy Dunlap , Chris Mason , bpf , linux-mm Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F0D091C0002 X-Stat-Signature: r9pfrcap7egr3wrz54csd8d7pb1wah66 X-HE-Tag: 1761701584-97669 X-HE-Meta: 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 8uTuWzTa 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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: On Sun, Oct 26, 2025 at 3:03=E2=80=AFAM Yafang Shao = wrote: > > The per-process BPF-THP mode is unsuitable for managing shared resources > such as shmem THP and file-backed THP. This aligns with known cgroup > limitations for similar scenarios [0]. > > Introduce a global BPF-THP mode to address this gap. When registered: > - All existing per-process instances are disabled > - New per-process registrations are blocked > - Existing per-process instances remain registered (no forced unregistrat= ion) > > The global mode takes precedence over per-process instances. Updates are > type-isolated: global instances can only be updated by new global > instances, and per-process instances by new per-process instances. ... > spin_lock(&thp_ops_lock); > - /* Each process is exclusively managed by a single BPF-THP. */ > - if (rcu_access_pointer(mm->bpf_mm.bpf_thp)) { > + /* Each process is exclusively managed by a single BPF-THP. > + * Global mode disables per-process instances. > + */ > + if (rcu_access_pointer(mm->bpf_mm.bpf_thp) || rcu_access_pointer(= bpf_thp_global)) { > err =3D -EBUSY; > goto out; > } You didn't address the issue and instead doubled down on this broken global approach. This bait-and-switch patchset is frankly disingenuous. 'lets code up some per-mm hack, since people will hate it anyway, and I'm not going to use it either, and add this global mode as a fake "fallback"...' The way the previous thread evolved and this followup hack I don't see a genuine desire to find a solution. Just relentless push for global mode. Nacked-by: Alexei Starovoitov Please carry it in all future patches.