From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A512F26E711; Wed, 1 Apr 2026 03:36:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775014582; cv=none; b=mJ9d+xsY3DsZ2896FpWch/xCEWdlzoJRyVXpGWaE9IT+g0R1E+QJeEibVAXPwyi7GZrrYBgGdmZRKH/xmGBM9srAWwKFW9vIk3I7Ct0ZbTojaCZhLpOwrAh8mdsTVrEuqrKXc40BAwhMxAUb9lWrPo1OcWIrXK3WJBNXmuwZwgk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775014582; c=relaxed/simple; bh=oM8MoDisKpDaXjO3RLPXLi7naizlxim+j7rzUdhBd8A=; h=Date:To:From:Subject:Message-Id; b=sfd9os7NYPTJriyeLfndh963vXykQk8PhpPkWua27gErpCUQeLHxw01BsuXGwYN0eYNAY9UOYYfyqAsTrnYm+4BBdK+8+Z3J4J9av893Tov1WjAnlltOFIgdlsSfm53gGZucnxEC5A5rRJr9UednPEbWoX8kzxyb+NO5opYzu3k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=T4V8k+rf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="T4V8k+rf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6700BC4CEF7; Wed, 1 Apr 2026 03:36:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1775014582; bh=oM8MoDisKpDaXjO3RLPXLi7naizlxim+j7rzUdhBd8A=; h=Date:To:From:Subject:From; b=T4V8k+rfOHVrE77sTng58yre4ghwaAdfCdbOUvfxqcMToKQGQxXQNNwwnIbQpHy1K MH7wFpaPNKMBWZbt4Ysfrj9QEdu59Yaq3/aUubCViQrI6VxtsPuIcAz/YIHHEw4n+M Iz36EbrhxlC2sekIcw4IYww1IRL/uiFM0ipV6Yag= Date: Tue, 31 Mar 2026 20:36:21 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,sj@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race.patch added to mm-hotfixes-unstable branch Message-Id: <20260401033622.6700BC4CEF7@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: Docs/admin-guide/mm/damon/reclaim: warn commit_inputs vs param updates race has been added to the -mm mm-hotfixes-unstable branch. Its filename is docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: SeongJae Park Subject: Docs/admin-guide/mm/damon/reclaim: warn commit_inputs vs param updates race Date: Sun, 29 Mar 2026 08:30:49 -0700 Patch series "Docs/admin-guide/mm/damon: warn commit_inputs vs other params race". Writing 'Y' to the commit_inputs parameter of DAMON_RECLAIM and DAMON_LRU_SORT, and writing other parameters before the commit_inputs request is completely processed can cause race conditions. While the consequence can be bad, the documentation is not clearly describing that. Add clear warnings. The issue was discovered [1,2] by sashiko. This patch (of 2): DAMON_RECLAIM handles commit_inputs request inside kdamond thread, reading the module parameters. If the user updates the module parameters while the kdamond thread is reading those, races can happen. To avoid this, the commit_inputs parameter shows whether it is still in the progress, assuming users wouldn't update parameters in the middle of the work. Some users might ignore that. Add a warning about the behavior. The issue was discovered in [1] by sashiko. Link: https://lkml.kernel.org/r/20260329153052.46657-2-sj@kernel.org Link: https://lore.kernel.org/20260319161620.189392-3-objecting@objecting.org [1] Link: https://lore.kernel.org/20260319161620.189392-2-objecting@objecting.org [3] Fixes: 81a84182c343 ("Docs/admin-guide/mm/damon/reclaim: document 'commit_inputs' parameter") Signed-off-by: SeongJae Park Cc: # 5.19.x Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/damon/reclaim.rst | 4 ++++ 1 file changed, 4 insertions(+) --- a/Documentation/admin-guide/mm/damon/reclaim.rst~docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race +++ a/Documentation/admin-guide/mm/damon/reclaim.rst @@ -71,6 +71,10 @@ of parametrs except ``enabled`` again. parameter is set as ``N``. If invalid parameters are found while the re-reading, DAMON_RECLAIM will be disabled. +Once ``Y`` is written to this parameter, the user must not write to any +parameters until reading ``commit_inputs`` again returns ``N``. If users +violate this rule, the kernel may exhibit undefined behavior. + min_age ------- _ Patches currently in -mm which might be from sj@kernel.org are mm-damon-sysfs-dealloc-repeat_call_control-if-damon_call-fails.patch mm-damon-core-fix-damon_call-vs-kdamond_fn-exit-race.patch mm-damon-core-fix-damos_walk-vs-kdamond_fn-exit-race.patch mm-damon-core-validate-damos_quota_goal-nid-for-node_mem_usedfree_bp.patch mm-damon-core-validate-damos_quota_goal-nid-for-node_memcg_usedfree_bp.patch mm-damon-core-use-time_in_range_open-for-damos-quota-window-start.patch docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race.patch docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch