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Mon, 22 Dec 2025 11:06:07 +0800 (CST) Received: from kwepemr500001.china.huawei.com (unknown [7.202.194.229]) by mail.maildlp.com (Postfix) with ESMTPS id CD56A40539; Mon, 22 Dec 2025 11:08:17 +0800 (CST) Received: from [10.174.179.179] (10.174.179.179) by kwepemr500001.china.huawei.com (7.202.194.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 22 Dec 2025 11:08:16 +0800 Message-ID: <68bffc9a-f067-4e67-87ee-9fea769950d5@huawei.com> Date: Mon, 22 Dec 2025 11:08:16 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/mempolicy: fix mpol_rebind_nodemask() for MPOL_F_NUMA_BALANCING To: "Huang, Ying" CC: , , , , , , , , , , , References: <20251213082911.1509735-1-tujinjiang@huawei.com> <87pl889uvg.fsf@DESKTOP-5N7EMDA> From: Jinjiang Tu In-Reply-To: <87pl889uvg.fsf@DESKTOP-5N7EMDA> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.179] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemr500001.china.huawei.com (7.202.194.229) X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 094E818000B X-Stat-Signature: 7dn1dujdtmsty46ruxeqipfbpfznrfn8 X-Rspam-User: X-HE-Tag: 1766372901-630865 X-HE-Meta: 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 xJj3RHvS eErjPXEAfXB9nKrhA5GXDITOu8M6apQVinNwZsHQinwd3e+88cnntcXxphZ9ot4TVL+OASz4QfkH5Z9EQKZM/m3EUlCUFIJqKvWA5REmoCabUqcPF+XZP9KNhFUhpwHGlB1Cx/XmOYhiJ7IbAsVq5ksqsGc12s1Ygrk3pdreJqZII3JM4L/43LqiBOXlGyM+qtklNueQZ6KXv8LwHQ5F64fQd4+JPk/+YR/PMVkBMUWe5TjPDb5vhBXe/n63PZIEaiOu5zN16uSOXOyZu/cqvbTh8+3bbeeytdCkVJbO/62KiLORQNI4ujse1mwm8Eys/lSvjFPK8iE2LGX6bfw2IgjKtk8WKoKtG3QDMISrNzPJhO68u0PfbuQPITmCAIalMsJFDD5a38glSbb04ziNxWjUN+JzLIpEstO4+oJz+NPl2AfIe/0XiZcNOAi6JeF8CWkFzTPuZvpAWbE1KDDF9YYNwxcpD8810CfAFbRxBef34Etg= 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: 在 2025/12/21 15:06, Huang, Ying 写道: > Hi, Jinjiang, > > Jinjiang Tu writes: > >> When mempolicy is rebound due to the process moves to a different cpuset >> context, or the set of nodes allowed by current cpuset context changes, >> mpol_rebind_nodemask() remaps the nodemask according to the old and new >> cpuset_mems_allowed by default. So, use mempolicy.w.cpuset_mems_allowed >> to store the old nodemask allowed by cpuset. >> >> MPOL_F_STATIC_NODES suppresses the node remap and intersects the user's >> passed nodemask and nodes allowed by new cpuset context. >> For MPOL_F_RELATIVE_NODES, the user's passed nodemask means node IDs that >> are relative to the set of node IDs allowed by the process's current >> cpuset. So, use mempolicy.w.user_nodemask to store the user's passed >> nodemask. >> >> commit bda420b98505 ("numa balancing: migrate on fault among multiple >> bound nodes") adds new flag MPOL_F_NUMA_BALANCING to enable NUMA balancing >> for MPOL_BIND, the behaviour of rebinding should be same with default >> befaviour. However, mpol_store_user_nodemask() returns true for >> MPOL_F_NUMA_BALANCING, leading to mempolicy.w.cpuset_mems_allowed stores >> the user's passed nodemask instead of cpuset_current_mems_allowed, and >> mpol_rebind_nodemask() remaps wrongly. > Good catch! Thanks for fixing this. > >> Fixes: bda420b98505 ("numa balancing: migrate on fault among multiple bound nodes") >> Signed-off-by: Jinjiang Tu >> --- >> include/uapi/linux/mempolicy.h | 6 ++++++ >> mm/mempolicy.c | 2 +- >> 2 files changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h >> index 8fbbe613611a..1802b6c89603 100644 >> --- a/include/uapi/linux/mempolicy.h >> +++ b/include/uapi/linux/mempolicy.h >> @@ -39,6 +39,12 @@ enum { >> #define MPOL_MODE_FLAGS \ >> (MPOL_F_STATIC_NODES | MPOL_F_RELATIVE_NODES | MPOL_F_NUMA_BALANCING) >> >> +/* >> + * MPOL_USER_NODEMASK_FLAGS is used to determine if nodemask passed by >> + * users should be used in mpol_rebind_nodemask(). >> + */ > This sounds a little internal in a user API header file. How about > something like below. Thanks, I have updated it in v2. > > /* Whether is a nodemask specified by user */ > >> +#define MPOL_USER_NODEMASK_FLAGS (MPOL_F_STATIC_NODES | MPOL_F_RELATIVE_NODES) >> + >> /* Flags for get_mempolicy */ >> #define MPOL_F_NODE (1<<0) /* return next IL mode instead of node mask */ >> #define MPOL_F_ADDR (1<<1) /* look up vma using address */ >> diff --git a/mm/mempolicy.c b/mm/mempolicy.c >> index 68a98ba57882..76da50425712 100644 >> --- a/mm/mempolicy.c >> +++ b/mm/mempolicy.c >> @@ -365,7 +365,7 @@ static const struct mempolicy_operations { >> >> static inline int mpol_store_user_nodemask(const struct mempolicy *pol) >> { >> - return pol->flags & MPOL_MODE_FLAGS; >> + return pol->flags & MPOL_USER_NODEMASK_FLAGS; >> } >> >> static void mpol_relative_nodemask(nodemask_t *ret, const nodemask_t *orig, > --- > Best Regards, > Huang, Ying