From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 72C49C43458 for ; Tue, 30 Jun 2026 14:50:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 495E86B0100; Tue, 30 Jun 2026 10:50:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 445DE6B0102; Tue, 30 Jun 2026 10:50:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 35E116B0104; Tue, 30 Jun 2026 10:50:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 1386D6B0100 for ; Tue, 30 Jun 2026 10:50:50 -0400 (EDT) Received: from smtpin24.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 815D31C35D7 for ; Tue, 30 Jun 2026 14:50:49 +0000 (UTC) X-FDA: 84936865818.24.C264425 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf25.hostedemail.com (Postfix) with ESMTP id D8C3FA0009 for ; Tue, 30 Jun 2026 14:50:47 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jWL4hHLB; spf=pass (imf25.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782831047; b=Elop05LvXwrLvOZhfGjmfoJfhFlVEdjYABB2R4KdZue5d6o/smnJErx8dqev8IuLD4B0RO aIcDgtY0YfBCGr+cRoqjaNQgHcAsu/gKQQOexLKn/ad2JHZFyoooYsQ07FA6ee8/8kly9Q EEs0YX01Ttc8YaYtDjqVGYKB6Rvh1eg= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782831047; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=JN7uBRPSVFgxr8lo91sF9pDzgRuTFCqZj5C/tFQXtwI=; b=A8XICSRHVBu8mJh9ZPtmCk9fRuTMhXitYtVEGZFjY5MH2e9FrcSKsCScS9sbXN/D/zNEM4 lUjAmRJtUHeDP7kzQiB1mdQT/wVN7uSn478BeUdSlVT45CE9scTdTdX4fuTUbH5MDraLze g454Thse8HmOH0LgKVyjQbBjnA6tyj8= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jWL4hHLB; spf=pass (imf25.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id EBA2641983; Tue, 30 Jun 2026 14:50:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8AC31F000E9; Tue, 30 Jun 2026 14:50:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782831046; bh=JN7uBRPSVFgxr8lo91sF9pDzgRuTFCqZj5C/tFQXtwI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=jWL4hHLBIgba6EJXfqBc82Vac+QTKWtgXVYmDn4/CYzwGjgF8051LfbfjGuWR+53M oHc2lPTCvbPPS70LBwkNnEmeX4YNzgq7bs0r22YzFBUuJJhGZMLPXqe17YPdmvwUQn gsRZmBovl5Dl7nHdXWwn4RHTJdVdYilXOGNW+2jFd5GT4qIQtfQF6N2qqPg86gqEMg 7tXop52CpsR70fffKJIcnu3BNt/RPZYZd6H5AauDkm1rAl3Rj3h20c/tuZa3rrA8qh 4F6a9qPeGa7YL1gBsu7ryBcng7jIzXP49YtG2oiNBro5F0URGeKEMvJDMebvykN0tu xGmJYpReCweQQ== From: SJ Park To: Igor Putko Cc: SJ Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/damon/vaddr: remove redundant RCU lock Date: Tue, 30 Jun 2026 07:50:39 -0700 Message-ID: <20260630145039.92859-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260630102400.reply-damon@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D8C3FA0009 X-Stat-Signature: ghfm8a8m1kt7mzx9x3zwkhym51q1zd3f X-HE-Tag: 1782831047-86184 X-HE-Meta: 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 qUuu4p1b 0tFY3QAU4NaGutdIHdRzUWHsoJReT0gD0RumIpLGm/hA3cfx7TYBujO/tEHSE1kJyKFLqngbhGG7pYL6mO59do5W73Qew4N8ScUmhdjy/iLbUe7bYhop3NMiG7L+4GD2YCs3IGUTm/UN13CD1ZsHgn76vvjJI41wN92thGooYAMSckReFxNSA1fOYXK1pRCfmmCfzY7t/7cUsrAOXFImZv4hx7ZRDO8jspLeL6jc78JPDiKbyPSpqRN7HRG/pIfDpiZ2JWOhYd5rTvP9RM1JVsgS2kA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 30 Jun 2026 17:25:22 +0300 Igor Putko wrote: > Hi SJ, > > Thanks for the reply and the pointers! Thank you for quick reply. Nonetheless, from the next time, please reply to a mail you are replying to, without top-posting [1]. Also, please wrap long lines for reasonable length of columns (say, 80 columns?) > Regarding the issue Sashiko AI flagged - I dug into damon/vaddr.c, and I think it's a real bug, but it's isolated to __damon_va_three_regions(). > damon_va_walk_page_range() is fine here, since lock_vma_under_rcu() handles stability on its own. __damon_va_three_regions() is the problematic one: right after mmap_read_lock(mm) is taken in the caller, it sets up a VMA_ITERATOR and runs for_each_vma(). But mmap_read_lock doesn't stop the OOM reaper from running concurrently, setting MMF_UNSTABLE, and leaving empty markers in the maple tree. Walking the tree in that state without a check_stable_address_space(mm) call could lead to a NULL pointer dereference. Thank you for detailed explanation. > Since this looks like a separate issue, I'll prepare a dedicated fix and send it as its own patch thread, so it doesn't hold up the current cleanup. Let me know if that approach works for you. Makes sense! [1] https://subspace.kernel.org/etiquette.html Thanks, SJ [...]