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AJvYcCUYtE7XND7PZKYhwASLqNBxexArAZhl0ohx9pGFyNEQxKpMv92AgLXePyH5brBObP3N6K6Qo7U2aQ==@kvack.org X-Gm-Message-State: AOJu0YyA7yQG6XZl4diNXvM/6mloCsOpxcKeRzHzbukCkP0Ann6fF3fT RX8fprsoeDnGps86i6y54OYTySDv2EGEFgNrMs9/cFdgVlOenl0PEMFDmz5VR2jXgrOTMeZwOWz UHjDUHsiCYFSDZ7IqM5gihgS4Wm0fu66ay1q/NBnL X-Gm-Gg: ASbGncvQP0TB3AJj+N6Qt1bkd88wO9TmohOzpqC+c91YuFaDkdqCJejrGvme4jDn2EA /cgfyUmlGeBNA39CX1fne9NW6JcNvj6yzIGqZ8CB2mYB4+ZfyzBI7sHB42r6NqUCy5JUKA8d8Fg 1He5VZ/kzwW+abhMTvRRWSbnAZ+/NpxkwC5UCI7Tp74eNAGK8SFgk/lbTxRlE/vFDvebn+/dMKo YiAknX2Ao8dAy4BBtL46tCe5Af+ZJglZYXAId4EWb4gfni3S4dAJNvvG+SfVfj+dt49DnE= X-Google-Smtp-Source: AGHT+IG8Ejwp50BSLB3roZMqzNKK3fdMxgSprm5enFcaaSJHsvTJPOSCN+WzTYJlIeeVTdHuRCAFpYySmA/1mTyvWxw= X-Received: by 2002:a05:6102:458f:b0:5cd:e513:384d with SMTP id ada2fe7eead31-5db7ddfd811mr330196137.0.1761605087687; Mon, 27 Oct 2025 15:44:47 -0700 (PDT) MIME-Version: 1.0 References: <20251021000852.2924827-1-pasha.tatashin@soleen.com> <20251021000852.2924827-3-pasha.tatashin@soleen.com> In-Reply-To: <20251021000852.2924827-3-pasha.tatashin@soleen.com> From: David Matlack Date: Mon, 27 Oct 2025 15:44:19 -0700 X-Gm-Features: AWmQ_bm9flIwjCIEktZFbqFsVLPTvjpFwWRND4pJrUQRYbrA52ouzPHjdJgenhI Message-ID: Subject: Re: [PATCH v3 2/3] liveupdate: kho: Increase metadata bitmap size to PAGE_SIZE To: Pasha Tatashin Cc: akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, pratyush@kernel.org, rdunlap@infradead.org, rppt@kernel.org, tj@kernel.org, jasonmiu@google.com, skhawaja@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C55FD80004 X-Stat-Signature: towyb11pwxfq7i7q9e3og4eppqjksesn X-Rspam-User: X-HE-Tag: 1761605088-278503 X-HE-Meta: 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 6ZhUbuyO q4I2NJy6x6sOFsKiMcWNkiKjegdtlrGJ10gI8QBQzlVWo6hMPkl158pbj8K+Uktvr6Re4ypAIWB4sXBV7Omt7TusgqaeHksNOr/UbVclhs9Hx4SJTvjomZqS6+N5pBTUeGUg2L/1RidYgxDl6zGpM9lSXsP/JDoljxKK3EFzKeHeE9QMl3fu1laNs3gX4CchIaHVcgyCUKNy/67F+cIIZHZLhVm2yLVRmoB5S2afSPZ1JUg9khvd1Csvqodte7yjMFNf6dkv4y3UBBURvxAJAwnlfGuPj+WCZuC7WXnpQaZ3a9fGQPzihbL8C4KsmeP7r7GR6NMryNEKrfpE= 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 Mon, Oct 20, 2025 at 5:09=E2=80=AFPM Pasha Tatashin wrote: > > KHO memory preservation metadata is preserved in 512 byte chunks which > requires their allocation from slab allocator. Slabs are not safe to be > used with KHO because of kfence, and because partial slabs may lead > leaks to the next kernel. Change the size to be PAGE_SIZE. > -#define PRESERVE_BITS (512 * 8) > +#define PRESERVE_BITS (PAGE_SIZE * 8) nit: A comment somewhere (maybe here?) about the requirement that KHO metadata are not stored on slabs would be helpful to avoid someone "optimizing" this back to 512 in the future.