From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 8C79F3E958F; Tue, 21 Jul 2026 05:22:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784611368; cv=none; b=WruBzw/RCDWRHzX1orRSvWXSHaLgvBLD/G2UQ4UC/9XoGSFsLT7YnZhCaC9JAgrcbnfQ27ePD9FxkiChOEHewCegZcJFV4nynZyc+41O+UtiY3+baV4wKE1P5Iyw33xkJL7PYM2XSMoZ1SQpYdtmy/3Ye4YW8N/OCpeczWYgVcE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784611368; c=relaxed/simple; bh=2uDdXvlfBlIhBOVQT1/oSY/Q/+XRLdg69Q8MyQIWFq8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jHB5Qh8joCIMda6+ICgMXSPkchcX7DvU3nFOfSOxFTZkVoUa8rHDejFeY6TVd47uzObbHOIaE3aT17I4fFhdQscQ+p0/wOp2sDObQSosw2mREzH3h1cqTFcwB0LJ5D3Cl5/MZnL5Xcf3vITsBLWyO34Pk42bRNeACTJ7+13oPjs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RjXSIQS3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RjXSIQS3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 059D21F000E9; Tue, 21 Jul 2026 05:22:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784611367; bh=kveFPF5cnocjHqe00S0Rn4FWt8I91aFY2LbGJXfoKes=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RjXSIQS3i4v9mSXoKqlI8xa7vth4IEeI4FqwSlEflTUIXopHNSDCDlPz/16JCZ4Kl i4R4SrSnPuYOGOBghyLTZxYhcON0aeNV1PRvzUXtEDPiJi9gxC57dDvSBssZkGYLHf z36rnUQ5aHy7VppyowTvJ1uPIN9sZQFiPtESG/iU+94btYGSLmVTgbM3mOctpeqk2M 1PGuyQZhuLXQgEMyJJDdtrob/Jnr1AKgL4uqaq8rFvHjQspJvloW68pchbihoOU0lD a6l4zzJwxb6al2vdGVnoSbGgT21aX+hOEghgYCc/Uhpmok+NOTUAYUcqluwpKw1f9R lXNIGFbFSL0RA== From: SJ Park To: stable@vger.kernel.org Cc: damon@lists.linux.dev, SeongJae Park , Andrew Morton Subject: [PATCH 6.12.y] mm/damon/core: always put unsuccessfully committed target pids Date: Mon, 20 Jul 2026 22:22:38 -0700 Message-ID: <20260721052238.163760-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <2026072031-shingle-buddy-1bbb@gregkh> References: <2026072031-shingle-buddy-1bbb@gregkh> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: SeongJae Park damon_commit_target() puts and gets the destination and the source target pids. It puts the destination target pid because it will be overwritten by the source target pid. It gets the source pid because the caller is supposed to eventually put the pids. In more detail, the caller will call damon_destroy_ctx() after damon_commit_ctx() to destroy the entire source context. And in this case, [f]vaddr operation set's cleanup_target() callback will put the pids. The commit operation is made at the context level. The operation can fail in multiple places including in the middle and after the targets commit operations. For any such failures, immediately the error is returned to the damon_commit_ctx() caller. If some or all of the source target pids were committed to the destination during the unsuccessful context commit attempt, those pids should be put twice. The source context will do the put operations using the above explained routine. However, let's suppose the destination context was not originally using [f]vaddr operation set and the commit failed before the ops of the source context is committed. The destination does not have the cleanup_target() ops callback, so it cannot put the pids via the damon_destroy_ctx(). As a result, the pids are leaked. The issue in the real world would be not very common. The commit feature is for changing parameters of running DAMON context while inheriting internal status like the monitoring results. The monitoring results of a physical address range ain't have things that are beneficial to be inherited to a virtual address ranges monitoring. So the problem-causing DAMON control would be not very common in the real world. That said, it is a supported feature. And damon_commit_target() failure due to memory allocation is relatively realistic [1] if there are a huge number of target regions. Fix by putting the pids in the commit operation in case of the failures. The issue was discovered [2] by Sashiko. Link: https://lore.kernel.org/20260605013849.83750-1-sj@kernel.org Link: https://lore.kernel.org/20260603112306.58490-1-akinobu.mita@gmail.com [1] Link: https://lore.kernel.org/20260320020056.835-1-sj@kernel.org [2] Fixes: 83dc7bbaecae ("mm/damon/sysfs: use damon_commit_ctx()") Signed-off-by: SeongJae Park Cc: # 6.11.x Signed-off-by: Andrew Morton (cherry picked from commit 6a66c557a2ab2609575bafd15e093669c05f9711) Signed-off-by: SJ Park --- mm/damon/core.c | 49 +++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 43 insertions(+), 6 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 2a6da49816526..416ef750ad140 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -938,10 +938,36 @@ static int damon_commit_target( return 0; } +/* + * damon_revert_target_commits() - revert unsuccessful target commits. + * @dst: Commit destination context + * @failed: Commit failed destination target + * @src: Commit source context + * + * Revert target states that changed by damon_commit_target(), and cannot be + * cleaned up by the destination context's ops.cleanup_target(). + */ +static void damon_revert_target_commits(struct damon_ctx *dst, + struct damon_target *failed, struct damon_ctx *src) +{ + struct damon_target *target; + + if (!damon_target_has_pid(src)) + return; + if (damon_target_has_pid(dst)) + return; + damon_for_each_target(target, dst) { + if (target == failed) + return; + put_pid(target->pid); + } +} + static int damon_commit_targets( struct damon_ctx *dst, struct damon_ctx *src) { struct damon_target *dst_target, *next, *src_target, *new_target; + struct damon_target *failed; int i = 0, j = 0, err; damon_for_each_target_safe(dst_target, next, dst) { @@ -950,8 +976,10 @@ static int damon_commit_targets( err = damon_commit_target( dst_target, damon_target_has_pid(dst), src_target, damon_target_has_pid(src)); - if (err) - return err; + if (err) { + failed = dst_target; + goto out; + } } else { if (damon_target_has_pid(dst)) put_pid(dst_target->pid); @@ -959,21 +987,28 @@ static int damon_commit_targets( } } + failed = NULL; damon_for_each_target_safe(src_target, next, src) { if (j++ < i) continue; new_target = damon_new_target(); - if (!new_target) - return -ENOMEM; + if (!new_target) { + err = -ENOMEM; + goto out; + } err = damon_commit_target(new_target, false, src_target, damon_target_has_pid(src)); if (err) { damon_destroy_target(new_target); - return err; + goto out; } damon_add_target(dst, new_target); } return 0; + +out: + damon_revert_target_commits(dst, failed, src); + return err; } /** @@ -1007,8 +1042,10 @@ int damon_commit_ctx(struct damon_ctx *dst, struct damon_ctx *src) * committing require putting pids). */ err = damon_set_attrs(dst, &src->attrs); - if (err) + if (err) { + damon_revert_target_commits(dst, NULL, src); return err; + } dst->ops = src->ops; return 0; -- 2.47.3