From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-m15594.qiye.163.com (mail-m15594.qiye.163.com [101.71.155.94]) (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 19DE21F3B87; Tue, 1 Sep 2026 08:16:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=101.71.155.94 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788250617; cv=none; b=SmFR13vCJTVCOfgkn1iLRtOXaSa+OKjFCOq5fiF/LjJmv41M/tOXVobQy/risxQXXu8zarj6l2a8dVuy6cniRYrx/NXqq8uUDqdIafbyCX/cRTXlfQ3MG78cQK+N1+pgHBpg8ZVNVSowu479HOE0zD3HkJ90CUJ13wFHUZG4sd0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788250617; c=relaxed/simple; bh=SsMxA1kjDySJWAU1JTBxcDQNRKDy8p32OnnCIFtDLz8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kfuXogyCR1JbLlInCK2aJdK3Sk9wUr5hGDNmAfDvRxQ5pFHe22Ck6KeudYI9soM3nO8oULyfOYl39pxwoomBq5CMYOc//uudm9jE4sM0kTeGROuui1AtAyMfQ85CklRXjxjc8bZ1jmoVXTVxB/o7t4j/066SBkx+Lg4ap2HLbOs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=easystack.cn; spf=pass smtp.mailfrom=easystack.cn; arc=none smtp.client-ip=101.71.155.94 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=easystack.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=easystack.cn Received: from [192.168.0.59] (unknown [218.94.118.90]) by smtp.qiye.163.com (Hmail) with ESMTP id 1e8dcbb65; Tue, 1 Sep 2026 16:01:21 +0800 (GMT+08:00) Message-ID: Date: Tue, 1 Sep 2026 16:01:20 +0800 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/8] mm/page_owner: Add PID/TGID/COMM and cgroup filtering To: "Lorenzo Stoakes (ARM)" Cc: Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan , Randy Dunlap , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260828031339.1270699-1-zhen.ni@easystack.cn> <20260828113654.d01abd8baed3f73e87506eb3@linux-foundation.org> <9fce3210-3548-4df3-ae00-730b666f5d57@easystack.cn> From: "zhen.ni" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-HM-Tid: 0aa05bfcacc80229kunma31d9b2c27c472 X-HM-MType: 1 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFJQjdXWRgWCB1ZQUpXWS1ZQUlXWQ8JGhUIEh9ZQVlCTExDVk5OGEJNS0gfTBhJGlYVFA kWGhdVGRETFhoSFyQUDg9ZV1kYEgtZQVlJSkNVQk9VSkpDVUJLWVdZFhoPEhUdFFlBWU9LSFVCQk lOS1VKS0tVSkJLQlkG 在 2026/9/1 15:27, Lorenzo Stoakes (ARM) 写道: > On Tue, Sep 01, 2026 at 02:34:34PM +0800, zhen.ni wrote: >> >> >> 在 2026/8/29 02:36, Andrew Morton 写道: >>> On Fri, 28 Aug 2026 08:03:38 +0100 "Lorenzo Stoakes (ARM)" wrote: >>> >>>> On Fri, Aug 28, 2026 at 11:13:31AM +0800, Zhen Ni wrote: >>>>> This patch series adds process and memory cgroup filtering support to >>>>> page_owner. Following the previous series that introduced print_mode and >>>>> NUMA node filters: >>>>> https://lore.kernel.org/linux-mm/20260707115411.1714314-1-zhen.ni@easystack.cn/ >>>>> >>>>> This series adds filtering capabilities to page_owner, allowing users to >>>>> filter output by specific processes and memory cgroups. Users can now >>>>> filter page_owner output by PID, TGID, COMM (with wildcard support), and >>>>> memory cgroup path. This makes page_owner debugging more focused and >>>>> efficient for tracking memory allocations in specific contexts. >>>> >>>> The majority of this cover letter feels like it should have been >>>> documentation put somewhere :) >>> >>> yes please. >>> >>> The only thing longer than the cover letter is the Sashiko report ;) >>> >>> https://sashiko.dev/#/patchset/20260828031339.1270699-1-zhen.ni@easystack.cn >>> >>> >> >> Hi Andrew, Lorenzo, >> >> Thanks for the review. >> >> I have analyzed all the Sashiko report findings. Some will be fixed in >> the next version, and for the rest I propose not to fix them, with >> reasons below. If there are no objections I will send v2 accordingly. >> >> Will be fixed in the next version: >> >> - mm/page_owner.c: drop the kstrdup() copy in parse_pid_t_list(); the >> token will be parsed in place. This also fixes a leak on the success >> path and a kfree() of an advanced (interior) pointer on the error >> path. cmp_int() will replace plain subtraction in cmp_pid_t(), and >> pid values exceeding PID_MAX_LIMIT will be rejected. >> - mm/page_owner.c: PAGE_OWNER will select GLOB so glob_match() is >> always linked in; parse_comm_list() will drop its kstrdup() copy the >> same way. >> - mm/page_owner.c: the cgroup path buffer will be allocated once per >> read() outside the page_ext RCU read-side critical section instead of >> per page inside get_page_memcg_info() (GFP_KERNEL allocations must >> not sleep there). The memcg= parsing branch will be guarded by >> CONFIG_MEMCG so kernels built without memcg reject the command >> instead of silently enabling a filter that never matches. >> - tools/mm/page_owner_filter.c: user-visible input errors (empty >> -p/-t/-c/-g arguments) will print error messages instead of exiting >> silently. >> - Documentation: the wildcard pattern in the -c example will be quoted >> to prevent shell glob expansion. >> >> Proposed not to fix, by design: >> >> 1. Shared-fd concurrent read/write races (READ_ONCE around the pid >> passed to bsearch, torn reads of pid/tgid lists, glob_match() racing >> comm rewrites, concurrent write() leading to state->memcg_path >> double-allocation): multi-threaded sharing of one page_owner fd is >> not a designed use of this interface. The filters are per-fd state >> meant to be configured once and then read, which is what the >> page_owner_filter tool does. Adding locking to the read path would >> put overhead into the per-page scan loop for no designed benefit. >> This matches the semantics of the original filter introduction. >> >> 2. No "clear filter" support (empty pid=/tgid= lists partially clearing >> proc filters, empty memcg=/nid= being rejected): write commands are >> incremental -- "keep the unmentioned filters" -- and there is no >> clear operation by design. To start over, close the fd and open a >> fresh one; the page_owner_filter tool already works this way. This >> also matches the semantics of the original filter introduction. >> >> 3. kcalloc() vs kmalloc_array() for new_comm_list: no consumer of the >> list reads past strscpy()'s NUL terminator, so uninitialized bytes >> are unreachable. >> >> 4. char cgroup_path[512] in validate_cgroup_path(): acknowledged that >> the kernel side accepts paths up to PATH_MAX (4096). The userspace >> check truncates an over-long path with snprintf() and then fails >> access(), so it is rejected, never silently accepted. Bumping the >> buffer to PATH_MAX would only serve pathological paths; realistic >> cgroup paths are well under 100 bytes, so 512 wastes nothing in >> practice. >> >> If this plan looks reasonable I will send v2. > > Sorry but this kind of 'summary', 'do you agree with the plan' email is not > acceptable. > > You have your feedback, reply to people like a human being directly to them, > thank you very much. > > At this point, based on past experience, I have to ask if you're using an LLM? > If so please disclose this as per kernel guidelines: > > https://docs.kernel.org/process/coding-assistants.html > https://docs.kernel.org/process/generated-content.html > >> >> Thanks, >> Zhen Ni > > -- > Cheers, Lorenzo > > Hi, Lorenzo I honestly don't understand what is wrong here. I spent two full days going through every single finding in the Sashiko report one by one, checking each against the code. In fact I am already working on v2 and testing the corresponding changes. What I don't understand is what "this kind of 'summary' email is not acceptable" is supposed to mean. If you disagree with any specific item, name it and we can discuss it -- but rejecting the whole thing outright, with just two documentation links and no specifics, is not something I can act on. Thanks, Zhen