From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 38002606A33B for ; Sun, 8 Nov 2026 19:22:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=JTBMMTbL Received: by kanga.kvack.org (Postfix) id E3C6C6B05C0; Sun, 8 Nov 2026 14:22:33 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CDA616B05BF; Sun, 8 Nov 2026 14:22:33 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B4CB16B05BE; Sun, 8 Nov 2026 14:22:33 -0500 (EST) 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 005336B05BB for ; Sun, 8 Nov 2026 14:22:32 -0500 (EST) Received: from smtpin13.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 227E71C27B1 for ; Sun, 8 Nov 2026 19:22:32 +0000 (UTC) X-FDA: 85412923344.13.161642F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf08.hostedemail.com (Postfix) with ESMTP id 654A4160003 for ; Sun, 8 Nov 2026 19:22:30 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=JTBMMTbL; spf=pass (imf08.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=1794165750; b=WLAIU0rr7xyUZUuoWwdiVMvJRnG0xUtw/2k0bh+S5py1uD3Vs5U2H/uaWtn6FljJzQLRO3 j40z0CPmQLb+C9AN1JD3OcVZjAAy6C91ILdJwJ23JdJXHJShoD5NKpBEj1qY5bY8Fg5WEV sDQ8BGLT4MrpOPelWjclKiNhDFzgbO8= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=JTBMMTbL; spf=pass (imf08.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-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1794165750; 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=7xZ+n0JvDN3hrYenLHVXLkTjZ+lK0ATIB/YUR73+pmo=; b=hcr53r+14ja/HAW/SCY2L12kCpwpz8oTyyYh24iH0C3ObD6mjT+Tc5UEKrRCWYhsuJvU2C s0p1OoNmhJAlrSQP3GDCDFowLvdqNpO8PgP54fLuX0SGQz+w2mnO5UhtpjoQJGbZrC2zqh /+x2zTav947xCFBDMj69/jldTvsk/CA= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 954B7434D4; Sun, 8 Nov 2026 19:22:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40A2B1F008A1; Sun, 8 Nov 2026 19:22:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794165749; bh=7xZ+n0JvDN3hrYenLHVXLkTjZ+lK0ATIB/YUR73+pmo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JTBMMTbLmUld9NcT0MS7oZ0BCP8jdLSQulpaGGpnXINKh66sW+/iol7TkF1T3exKz //Fu+UMBhlvYt1A50YESr532I14L6CUWHmrZvYGcCqIakeRopKz4ruUtOaUIePHsU3 zc2c4mO3304UNg4o4VPPoGSfXBdvgARmm9JkH6Eu+TwQpTPbizhqCl45na1haSDuL/ TVvif5LeaTXjBL0UllBP56f7WUpx3dWIpGomfHPj+alf7ack/dgXtu8h84cKRE8WWF 7Vf7z4Er4lsuS6v9sa3ap3lSh9J1SHclSLbIgXTq60u/pSz9VBkUYghIJiuWoCj8wd HTA2n9CUrAFXg== From: SJ Park To: stable@vger.kernel.org Cc: SJ Park , Andrew Morton , Usama Arif , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 6.18.y 1/5] mm/damon/core: skip applying scheme if region split for quota fails Date: Sun, 8 Nov 2026 11:22:16 -0800 Message-ID: <20261108192221.114362-2-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261108192221.114362-1-sj@kernel.org> References: <20261108192221.114362-1-sj@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: camst3ggr1id3tfmwhkrmh7j39cdh36d X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 654A4160003 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794165750-210397 X-HE-Meta: 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 Qz19PFdT /kfF9dD2evx92zNgXBF+N6zP3I2fCQu9QRkyZn0UEzzwy0qf+F19R3McBcEDY6np5kvlqzf2HmC4FcIncfmXMTxdp63+h17dz4P0HELuFtc/OQhYz3MIezgLrIQQ0nBVRrfTGM6w3oMvLibAfJxVIaCgybwUkacgtOgW9IcDqRd/5UOkdrgvil+PGeeLlGMt3xUEsb2mzmWgsf+IM9SSAKVEShoV7Pj6mDrJ96JMIgNTlHOvZSFn9iq86TEq+vSIspxyhUQXSfNYJ90uj6Hb8aazlK7E5i+jqsQHXHIyVd9EqyamoEIwzRfSZhg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Patch series "mm/damon: fix DAMOS bugs in core, paddr and vaddr". Fix misc bugs of DAMOS. Patch 1 makes DAMOS less stress memory allocator under extreme situation. Patches 2 and 3 fix wrong folios walking in DAMON_PADDR. Patches 4 and 5 fix wrong folios walking in DAMON_VADDR. Patches 6-8 handle extreme and unlikely memory situations that can cause divide by zero and underflow. All bugs are discovered by Sashiko. This patch (of 8): damos_apply_scheme() splits a region and apply the action to the subregion if it is needed for not violating the quota. The split operation (damon_split_region_at()) could fail for allocation failure. In the case, the quota could be violated. From the user's perspective, DAMOS becomes more aggressive than expected under the extreme situation. Handle the failure. The user impact is not critical. The failure of damon_split_region_at() is unlikely since it is arguably too small to fail. Also DAMOS being aggressive is limited to the single region. Users can set min_nr_regions to set the maximum size of each region. If it is reasonably set, the transient overhead shouldn't be critical. The issue was discovered [1] by Sashiko. 6.18.y porting notes. Modify damon_split_region_at() to return failures. It is a part of commit c60874860762 ("mm/damon/core: handle region split failure in apply_min_nr_regions()"). Without it, build fails. Link: https://lore.kernel.org/20260901131850.98037-1-sj@kernel.org Link: https://lore.kernel.org/20260901131850.98037-2-sj@kernel.org Link: https://lore.kernel.org/20260718171523.87547-1-sj@kernel.org [1] Fixes: 2b8a248d5873 ("mm/damon/schemes: implement size quota for schemes application speed control") Signed-off-by: SJ Park Signed-off-by: Andrew Morton Cc: Usama Arif Cc: # 5.16.x (cherry picked from commit 90c2fa6adfed7abe0935506a43cdff3a05c1fff0) Signed-off-by: SJ Park --- mm/damon/core.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 8fa788b0d709c..4c536a9b958e4 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1700,7 +1700,7 @@ static void kdamond_tune_intervals(struct damon_ctx *c) damon_set_attrs(c, &new_attrs); } -static void damon_split_region_at(struct damon_target *t, +static int damon_split_region_at(struct damon_target *t, struct damon_region *r, unsigned long sz_r); static bool __damos_valid_target(struct damon_region *r, struct damos *s) @@ -2000,7 +2000,8 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t, c->min_sz_region); if (!sz) goto update_stat; - damon_split_region_at(t, r, sz); + if (damon_split_region_at(t, r, sz)) + goto update_stat; } if (damos_filter_out(c, t, r, s)) return; @@ -2454,15 +2455,17 @@ static void kdamond_merge_regions(struct damon_ctx *c, unsigned int threshold, * * r the region to be split * sz_r size of the first sub-region that will be made + * + * Return: 0 on success, negative error code otherwise. */ -static void damon_split_region_at(struct damon_target *t, +static int damon_split_region_at(struct damon_target *t, struct damon_region *r, unsigned long sz_r) { struct damon_region *new; new = damon_new_region(r->ar.start + sz_r, r->ar.end); if (!new) - return; + return -ENOMEM; r->ar.end = new->ar.start; @@ -2472,6 +2475,7 @@ static void damon_split_region_at(struct damon_target *t, new->nr_accesses = r->nr_accesses; damon_insert_region(new, r, damon_next_region(r), t); + return 0; } /* Split every region in the given target into 'nr_subs' regions */ -- 2.47.3