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Sat, 22 Nov 2025 17:53:18 -0800 (PST) Date: Sun, 23 Nov 2025 01:53:17 +0000 From: Wei Yang To: Zi Yan Cc: David Hildenbrand , Lorenzo Stoakes , Andrew Morton , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Miaohe Lin , Naoya Horiguchi , Wei Yang , Balbir Singh , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/4] mm/huge_memory: make min_order_for_split() always return an order Message-ID: <20251123015317.3pommq5h54xnau7e@master> Reply-To: Wei Yang References: <20251122025529.1562592-1-ziy@nvidia.com> <20251122025529.1562592-4-ziy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251122025529.1562592-4-ziy@nvidia.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 8E897180008 X-Stat-Signature: md5j5cyztkm1b7xhwi93b97j6gf6g7cq X-Rspam-User: X-HE-Tag: 1763862800-87007 X-HE-Meta: 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 XNsZWomt aQexAoBHes3uw71jAai9vp5nkC737lQIkc8+K7ppJFy5a+sBDAzX171NS2UBCZgeJku2mLxKEXevPL2clMgAmAWmUZvQw6lH3Wms/59wYATOiAiO7C6FmgIJJBZNtEIbi+ZWEA40FCiTgBx2VU1szK3xS+YkVkH7KfOp05jDzgFgDHQSzQpDVvCgxkQzqd8WqggUA1eqmxbUoCQZvH/db3PPrEvMNHk0z/AaBmTgkNxpmK8dsWkftF4RrmtmjHNKkIzqBPJtkl7oX87qEBtsVIVptXSyWnxcA0BDJMbo3T7Z9QjPPzuCZZjinz96CB7DCEYtLfP002NNtwNbIO84RKOMKp02FAhjzMxHAMDsdoX1DeNx9kIKCsT+APnChH4LllhqubW2zmyx1AVConaVhpc3dQDe0+coyT4Qv2sdw5SjxYTbcsOUFwWPbINeQGzIqGjMpoJCOY7KCho4ZkAl2HFA7Ln2ma3BIKsgN482SFKaiMTJZjIRZGuaTOJyWssMmnxb21r5oJuaVFeYW0vwfJboh4jtdzE8VtTW+wWFHkJq6+CJgdaSxg77r9cMf+NHWM7OnrggphrIRXvVXUTxBKbztPJDqpYnTfpSaSjcZISsC35L5IDs3RyLL7yfDdBt+9zA8biQgknZefBjo56TAswl8xdX2gET7aU/bS1Ukya8ZG10sU2Irrl/XMNZzco4Jytn0tSqAGIURxjPbrTUuKfYYxqxXVFcm8accMvb6Ed61t5T7sDB+pD718xcHwgRza3vdfV7cY7L4sEI/Z/wfqRiu1ViuAFwIolHXxJvnY2qTbxc= 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 Fri, Nov 21, 2025 at 09:55:28PM -0500, Zi Yan wrote: >min_order_for_split() returns -EBUSY when the folio is truncated and cannot >be split. In commit 77008e1b2ef7 ("mm/huge_memory: do not change >split_huge_page*() target order silently"), memory_failure() does not >handle it and pass -EBUSY to try_to_split_thp_page() directly. >try_to_split_thp_page() returns -EINVAL since -EBUSY becomes 0xfffffff0 as >new_order is unsigned int in __folio_split() and this large new_order is >rejected as an invalid input. The code does not cause a bug. >soft_offline_in_use_page() also uses min_order_for_split() but it always >passes 0 as new_order for split. > >Fix it by making min_order_for_split() always return an order. When the >given folio is truncated, namely folio->mapping == NULL, return 0 and let >a subsequent split function handle the situation and return -EBUSY. > >Add kernel-doc to min_order_for_split() to clarify its use. > >Signed-off-by: Zi Yan LGTM, Thanks Reviewed-by: Wei Yang -- Wei Yang Help you, Help me