From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C01EAB667; Mon, 5 Feb 2024 05:50:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707112251; cv=none; b=UntQzH8ZXCDiUsP1PmUus0VIXTHRCvym61TNVEOGU4I1g/AxtJSfBb0GtJXx2QnV4CKXAl7dR1LKvt8/L/2TTfmhfro6qYnYjn7USrk937l8ABzPL/reETL0rzop3rjhu5wW2RnRSxm8w7F8DxKVQbG0hwvK2wLYVg2f99UMJBA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707112251; c=relaxed/simple; bh=lSM7C+vUc6UhPUqzZ2Tj67xDB4u+cxvZTB1BWRh9jbE=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=pHSmu5Cx8w+ZBZxNwZjsdBGMuG//PWLCQQrxf6eKcKqR0R5+IoK6nEX17q1I07OaWRKNvgrE3waeSI4wk5ZfyOHBl43EmBX5wp9LgEXgH0xzVyJtWXAnB1pdhIajENb9oS8kIbWatvp9xGzQaIQIjYluFqtEsJGovTiy4WYzFpg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=UYbEG4ns; arc=none smtp.client-ip=192.198.163.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="UYbEG4ns" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1707112249; x=1738648249; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=lSM7C+vUc6UhPUqzZ2Tj67xDB4u+cxvZTB1BWRh9jbE=; b=UYbEG4ns4Vr6SuQRLbaWTwCk7SsjxNJslorXD6lbt5q61j9JojRgkQcL CjQTy1CSAzlYkpWUKt0ZNA81vMBPg1xARHH/jXwYLph7+vGGGV+5S9eiP acpEdVzcDVT9SV1Ev9fD2s281iErCzhxhV4qB8aqdLVM13iSljA8Su477 BeGd+JZXEeqHYDCzrugQy66/Om8fb4CkAGVVOzWwKizez/ykLdbdom0LN TrTguBP8KfIHw66+t+kzHKT3oElPkkv+4xdl/QKerBx2Wxk+sANLtuM1Z MZNQg4W8OsKznZjk/2JAjohZUVBd/sNU1UHO+CK4xNi+ywEN86k+FF+kV w==; X-IronPort-AV: E=McAfee;i="6600,9927,10974"; a="25900774" X-IronPort-AV: E=Sophos;i="6.05,242,1701158400"; d="scan'208";a="25900774" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Feb 2024 21:50:47 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,242,1701158400"; d="scan'208";a="38038147" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Feb 2024 21:50:41 -0800 From: "Huang, Ying" To: Gregory Price Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, corbet@lwn.net, akpm@linux-foundation.org, gregory.price@memverge.com, honggyu.kim@sk.com, rakie.kim@sk.com, hyeongtak.ji@sk.com, mhocko@kernel.org, vtavarespetr@micron.com, jgroves@micron.com, ravis.opensrc@micron.com, sthanneeru@micron.com, emirakhur@micron.com, Hasan.Maruf@amd.com, seungjun.ha@samsung.com, hannes@cmpxchg.org, dan.j.williams@intel.com Subject: Re: [PATCH v5 4/4] mm/mempolicy: protect task interleave functions with tsk->mems_allowed_seq In-Reply-To: <20240202170238.90004-5-gregory.price@memverge.com> (Gregory Price's message of "Fri, 2 Feb 2024 12:02:38 -0500") References: <20240202170238.90004-1-gregory.price@memverge.com> <20240202170238.90004-5-gregory.price@memverge.com> Date: Mon, 05 Feb 2024 13:48:44 +0800 Message-ID: <87r0hr31hf.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Gregory Price writes: > In the event of rebind, pol->nodemask can change at the same time as an > allocation occurs. We can detect this with tsk->mems_allowed_seq and > prevent a miscount or an allocation failure from occurring. > > The same thing happens in the allocators to detect failure, but this > can prevent spurious failures in a much smaller critical section. > > Suggested-by: "Huang, Ying" > Signed-off-by: Gregory Price > --- > mm/mempolicy.c | 31 +++++++++++++++++++++++++------ > 1 file changed, 25 insertions(+), 6 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index d8cc3a577986..ed0d5d2d456a 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1878,11 +1878,17 @@ bool apply_policy_zone(struct mempolicy *policy, enum zone_type zone) > > static unsigned int weighted_interleave_nodes(struct mempolicy *policy) > { > - unsigned int node = current->il_prev; > - > - if (!current->il_weight || !node_isset(node, policy->nodes)) { > + unsigned int node; > + unsigned int cpuset_mems_cookie; > + > +retry: > + /* to prevent miscount use tsk->mems_allowed_seq to detect rebind */ > + cpuset_mems_cookie = read_mems_allowed_begin(); > + node = current->il_prev; > + if (!node || !node_isset(node, policy->nodes)) { ~~~~~ !current->il_weight ? -- Best Regards, Huang, Ying > node = next_node_in(node, policy->nodes); > - /* can only happen if nodemask is being rebound */ > + if (read_mems_allowed_retry(cpuset_mems_cookie)) > + goto retry; > if (node == MAX_NUMNODES) > return node; > current->il_prev = node; > @@ -1896,8 +1902,14 @@ static unsigned int weighted_interleave_nodes(struct mempolicy *policy) > static unsigned int interleave_nodes(struct mempolicy *policy) > { > unsigned int nid; > + unsigned int cpuset_mems_cookie; > + > + /* to prevent miscount, use tsk->mems_allowed_seq to detect rebind */ > + do { > + cpuset_mems_cookie = read_mems_allowed_begin(); > + nid = next_node_in(current->il_prev, policy->nodes); > + } while (read_mems_allowed_retry(cpuset_mems_cookie)); > > - nid = next_node_in(current->il_prev, policy->nodes); > if (nid < MAX_NUMNODES) > current->il_prev = nid; > return nid; > @@ -2374,6 +2386,7 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp, > struct page **page_array) > { > struct task_struct *me = current; > + unsigned int cpuset_mems_cookie; > unsigned long total_allocated = 0; > unsigned long nr_allocated = 0; > unsigned long rounds; > @@ -2391,7 +2404,13 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp, > if (!nr_pages) > return 0; > > - nnodes = read_once_policy_nodemask(pol, &nodes); > + /* read the nodes onto the stack, retry if done during rebind */ > + do { > + cpuset_mems_cookie = read_mems_allowed_begin(); > + nnodes = read_once_policy_nodemask(pol, &nodes); > + } while (read_mems_allowed_retry(cpuset_mems_cookie)); > + > + /* if the nodemask has become invalid, we cannot do anything */ > if (!nnodes) > return 0;