From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.237 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794453595; b=pAg+p0Hg3BxjcGJ4kCWIc8MjF+qb2K0k0T4ABgVHdMFJlnDLlq/7uJGN4ltDp/qYJtEn 5sBT6lwovzivwi/vlh2Ub5jr4ZGzPemABDb7mSvj+uQ8pE2oXA5le/9cHJ4uUOQYW19FJ hwCO3jxQGsJux4g5hkCcNvEbNs2uHjys9JRInZY/B0HPZC63FJOqQr/m0x0Kg6jSjJ6bL KfPkyfliaL568IFaFtj7yV1eUq4wb6asLquPkqpxMJQgIco9jIWTn/TWtYztZ5FK8OqZo Cv1/iujXJ4BcllBS7DF9u/pCG2wyn+ObtNJZCIuhHEMLEI1ilaDk3kU+2HU1K71x9/g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794453595; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-Id: X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=9GvtRYRbd4CoqS+rXVERn+wNNfou0jJHIITEO+OkwsU=; b=eudC4mq0t/IxVUpL39dsXdRZcO+s9Sop4QuumCAZdN+hYV9clft/GMwj7lZVoB0QcLqA RXopiRUMi4diazmym2h3MWys61E/lExsaoR0OfBbjWcewllX7s7waoUY4ZTYN5hUOXELd zUcxBVrk25lIVrlUzLL5S2fnuIbmPzJ/Iy+BMAbxtj70utzAT1Ev1kPlXTABS+V1gAha/ lLBwKgmgrjxQRDfxIgxUqqGQYsa74vhYuMDuew/4qG2St6S0jKnjElEOSDBhuJk1kt/yt ERLKFyuTAshGOuMnlni6eSGtih8rjjv++8cEVLiYnZ1UcQwMSM8fBJNg5NMP66gdHwQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=thsqYINx; arc=none smtp.remote-ip=95.215.58.237 Received: from mta1.migadu.com (out-237.mta1.migadu.com [95.215.58.237]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32B8B606A894 for ; Thu, 12 Nov 2026 03:19:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 32B8B606A894 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=thsqYINx X-Envelope-To: cgroups@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=quEt/JnCI1mA6YioreHp+12gFD3nu+Bp5iPxfIGrlqA=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794453592; v=1; x=1795058392; b=thsqYINxIIMX7ZSD1VPb9o8FuSF4meBFXdGjDOhpOIpXgNC+fvIqgmP8AFterEGZkIHqg8CM kKQ0qNpa4gZNNPe43hLH1PtIsYYaDXNRsQnN0TKIWnfd9jHXbKaE97QjeVo+SdkYKs/+12SqA+b Kl1hddiYz/58DjLmcx9aOgeI= X-Envelope-To: cgroups@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 134bc58838378308; Thu, 12 Nov 2026 03:19:52 +0000 X-Mizu-Trace-ID: 134bc58838378308 X-Migadu-Flow: FLOW_OUT From: Ridong Chen To: Waiman Long , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Shuah Khan Cc: Ridong Chen , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Guopeng Zhang , Ridong Chen Subject: [PATCH for-7.4-fixes v4 2/2] cpuset: generalize the validate_partition() interface Date: Thu, 12 Nov 2026 11:19:31 +0800 Message-Id: <20261112031931.2815548-3-ridong.chen@linux.dev> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261112031931.2815548-1-ridong.chen@linux.dev> References: <20261112031931.2815548-1-ridong.chen@linux.dev> X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ridong Chen Refactor validate_partition() to take the parent partition, the new partition root state, the new effective exclusive CPUs and the CPUs to be deleted, instead of a trial cpuset. A NULL parent stands for a remote partition, whose CPUs come from top_cpuset. This makes the interface flexible enough to handle both local and remote partition validation. This also fixes a false PERR_NOCPUS error when expanding a remote partition. The no CPU left for tasks check in partition_cpus_change() is done against the cgroup parent, but the CPUs of a remote partition come from top_cpuset, not from its parent. For example, on a 4-CPU system: echo 2-3 > P/cpuset.cpus echo 2-3 > P/cpuset.cpus.exclusive echo 2-3 > P/C/cpuset.cpus echo 2 > P/C/cpuset.cpus.exclusive echo root > P/C/cpuset.cpus.partition (a task in P) echo 2-3 > P/C/cpuset.cpus.exclusive cat P/C/cpuset.cpus.partition root invalid (Parent is not a partition root) The effective_cpus of P is 3, a subset of the new exclusive CPUs 2-3 of C, and P has a task, so the expansion is rejected. However, P is not a partition root and does not give any CPU to C, and top_cpuset still has CPUs 0-1 for the task. Enabling C directly with exclusive CPUs 2-3 succeeds, as remote_partition_enable() checks top_cpuset instead. The no CPU left for tasks check now uses the given parent instead of parent_cs(cs), and top_cpuset for a remote partition, as that is where its CPUs are taken from. The housekeeping conflict check is folded into validate_partition(). It is skipped when the parent is not a valid partition root, as @cs can't be a valid local partition in that case. Use the new interface for local partition enablement in update_parent_effective_cpumask() and in partition_cpus_change(), replacing the open-coded checks there. The order of the checks is now the same for both paths: empty CPUs, housekeeping conflict, then no CPU left for tasks. Add a test case to test_cpuset_prs.sh for the remote partition expansion above. Fixes: 181c8e091aae ("cgroup/cpuset: Introduce remote partition") Signed-off-by: Ridong Chen --- kernel/cgroup/cpuset.c | 119 +++++++++--------- .../selftests/cgroup/test_cpuset_prs.sh | 5 + 2 files changed, 64 insertions(+), 60 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index c7d4cfb615b7..7e374210c123 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1414,6 +1414,48 @@ static bool prstate_housekeeping_conflict(int new_prs, int parent_prs, return res; } +/** + * validate_partition - Validate a cpuset partition configuration + * @cs: The cpuset to validate + * @parent: Parent partition of @cs, NULL for remote partition + * @new_prs: The proposed new partition root state + * @new_excpus: The new effective exclusive CPUs mask to validate + * @del: exclusive CPUs to be deleted from @cs, can be NULL + * + * A remote partition gets its CPUs from top_cpuset, so top_cpuset is used + * as the parent when @parent is NULL. + * + * The housekeeping check is skipped if @parent is not a valid partition + * root as @cs can't be a valid local partition in that case. + * + * Return: PRS error code (0 if valid, non-zero error code if invalid) + */ +static enum prs_errcode validate_partition(struct cpuset *cs, + struct cpuset *parent, int new_prs, + struct cpumask *new_excpus, + struct cpumask *del) +{ + int parent_prs; + + if (new_prs == PRS_MEMBER) + return PERR_NONE; + + if (cpumask_empty(new_excpus)) + return PERR_INVCPUS; + + if (!parent) + parent = &top_cpuset; + parent_prs = parent->partition_root_state; + if (parent_prs > 0 && + prstate_housekeeping_conflict(new_prs, parent_prs, new_excpus, del)) + return PERR_HKEEPING; + + if (tasks_nocpu_error(parent, cs, new_excpus)) + return PERR_NOCPUS; + + return PERR_NONE; +} + /* * cpuset_update_sd_hk_unlock - Rebuild sched domains, update HK & unlock * @@ -1934,18 +1976,10 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) { new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED; - /* - * Enabling partition root is not allowed if its - * effective_xcpus is empty. - */ - if (cpumask_empty(tmp->delmask)) - return PERR_INVCPUS; - - if (prstate_housekeeping_conflict(new_prs, parent_prs, tmp->delmask, NULL)) - return PERR_HKEEPING; - - if (nocpu) - return PERR_NOCPUS; + part_error = validate_partition(cs, parent, new_prs, + tmp->delmask, NULL); + if (part_error) + return part_error; /* * This function will only be called when all the preliminary @@ -2428,32 +2462,6 @@ static int parse_cpuset_cpulist(const char *buf, struct cpumask *out_mask) return 0; } -/** - * validate_partition - Validate a cpuset partition configuration - * @cs: The cpuset to validate - * @trialcs: The trial cpuset containing proposed configuration changes - * - * If any validation check fails, the appropriate error code is set in the - * cpuset's prs_err field. - * - * Return: PRS error code (0 if valid, non-zero error code if invalid) - */ -static enum prs_errcode validate_partition(struct cpuset *cs, struct cpuset *trialcs) -{ - struct cpuset *parent = parent_cs(cs); - - if (cs_is_member(trialcs)) - return PERR_NONE; - - if (cpumask_empty(trialcs->effective_xcpus)) - return PERR_INVCPUS; - - if (tasks_nocpu_error(parent, cs, trialcs->effective_xcpus)) - return PERR_NOCPUS; - - return PERR_NONE; -} - /** * partition_cpus_change - Handle partition state changes due to CPU mask updates * @cs: The target cpuset being modified @@ -2467,33 +2475,24 @@ static void partition_cpus_change(struct cpuset *cs, struct cpuset *trialcs, struct tmpmasks *tmp) { enum prs_errcode prs_err; - int parent_prs = is_remote_partition(cs) - ? PRS_ROOT : parent_cs(cs)->partition_root_state; + struct cpuset *parent = is_remote_partition(cs) ? NULL : parent_cs(cs); if (cs_is_member(cs)) return; - prs_err = validate_partition(cs, trialcs); - if (!prs_err && (parent_prs > 0) && - !cpumask_empty(trialcs->effective_xcpus)) { - int prs = cs->partition_root_state; - - /* - * Check for housekeeping conflict by passing the whole - * effective_xcpus as well as those CPUs that are to be - * removed from cs as delmask. - */ - if (prs > 0) - cpumask_andnot(tmp->delmask, cs->effective_xcpus, - trialcs->effective_xcpus); - else - cpumask_clear(tmp->delmask); - - if (prstate_housekeeping_conflict(prs, parent_prs, - trialcs->effective_xcpus, tmp->delmask)) - prs_err = PERR_HKEEPING; - } + /* + * Check for housekeeping conflict by passing the whole + * effective_xcpus as well as those CPUs that are to be + * removed from cs as delmask. + */ + if (is_partition_valid(cs)) + cpumask_andnot(tmp->delmask, cs->effective_xcpus, + trialcs->effective_xcpus); + else + cpumask_clear(tmp->delmask); + prs_err = validate_partition(cs, parent, trialcs->partition_root_state, + trialcs->effective_xcpus, tmp->delmask); if (prs_err) { WRITE_ONCE(cs->prs_err, prs_err); trialcs->prs_err = prs_err; diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index 1e9e6b4c6f7b..1397ec428c46 100755 --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh @@ -707,6 +707,11 @@ REMOTE_TEST_MATRIX=( " C1-4:P1 C5-6 C1-2 . C5 . \ . P1 P1 . O5=0 . p1:3-4|p2:6|c11:1-2|c12:3-4|c21:6|c22:6 \ p1:P1|p2:P1|c11:P1" + # Expanding a remote partition should check top cpuset, not its member + # parent, for the no CPU left for tasks error. + " CX2-3:T . C2-3:X2:P1 . . . \ + . . X2-3 . . . p1:1,4-7|c11:2-3 \ + p1:P0|c11:P1" ) # -- 2.34.1