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 81DE2356766; Tue, 8 Sep 2026 19:00:18 +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=1788894019; cv=none; b=iRsj4oeMMhW3Al402NUGe0D/cLR/gIxdJHtF8M6YbdhvNOvT3s16J1Z3t4A5kRDwHxW7c3RAgpkCNkFXyPu808TS86RGagsN0TBC/lLIW09WQoU/X1Uqrp1X1vY+d7cV88Z2v+RqZHw1xjM08u27jiuL1A9zUMb664TDARqYDFc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788894019; c=relaxed/simple; bh=TkMUznrXurED6ouL2kpIGcGJ6tGr5yarQgd2lU0tR0Q=; h=Date:To:From:Subject:Message-Id; b=dt+LLW6aF03++wEON5EQhci3q/bfKs0oSfELalg5Ko9usD6/ynXbbBk7EFRXGjAFI/qeY7J34lP2ggzOjbsIDOJ+uLgiUciASs9yZt3lwJRchRquIJW20XPAA4/RlHtrF82Eje3m1DQWTIA0qdNmnGJdRO6KvqLmA7z/6bFaTXc= 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=Tdu/efGa; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Tdu/efGa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D34C11F00A3F; Tue, 8 Sep 2026 19:00:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788894017; bh=btL9acUu57VC72oDspwZpJDiNzFfNPHfnyRiBllBNvY=; h=Date:To:From:Subject; b=Tdu/efGapWXcAUedOk4nJnGegLbPoX83HtbhUf0XVclt9Mqj0jZPYmjNQYGUjdl7K /h3pyXtqYZhcaey2G5FIG7amiMloAhCVQ840FVKlM2dfyG7DJEgNaYxhGhX88jdlYe qaqprgjMl7Gi2dmUwSetc7oOHJ+5JrKbjOyGo0vs= Date: Tue, 08 Sep 2026 12:00:17 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,sj@kernel.org,aethernet65535@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-damon-core-fix-unconditionally-skip-last-region.patch added to mm-hotfixes-unstable branch Message-Id: <20260908190017.D34C11F00A3F@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/damon/core: fix unconditionally skip last region has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-core-fix-unconditionally-skip-last-region.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-fix-unconditionally-skip-last-region.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: Liew Rui Yan Subject: mm/damon/core: fix unconditionally skip last region Date: Tue, 8 Sep 2026 06:47:38 -0700 Once quota set, the charge_{target,addr}_from unconditionally skips and resets at the last region of the tracked target, so the last region can be skipped even when it has not been processed. Example: 1. Target has 2 regions: R1 (0-100 bytes) and R2 (100-200 bytes). 2. Quota is configured to process only 100 bytes per window. 3. Window 1: Processes R1 (0-100). Quota is full. charge_{target, addr}_from is saved at (Target, 100). 4. Window 2: The loop reaches R2. Because R2 is damon_last_region(t), the old code unconditionally returns true, skipping R2 entirely and resetting the charge_{target,addr}_from. Result: R2 is permanently skipped even though it has never been processed. However, it is important to note that this is a very minor issue. This is because it is triggered only when the previous window saved/kept charge_{target,addr}_from, and in the next window, all regions except the last region were skipped by damos_skip_charged_region(). Fix this by only resetting the charge_{target,addr}_from when last region is reached, only skipping when it is applied or cannot split. Link: https://lore.kernel.org/20260908134739.96919-1-sj@kernel.org Fixes: 50585192bc2e ("mm/damon/schemes: skip already charged targets and regions") Signed-off-by: Liew Rui Yan Reviewed-by: SJ Park Signed-off-by: SJ Park Cc: # v5.16.x Signed-off-by: Andrew Morton --- mm/damon/core.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) --- a/mm/damon/core.c~mm-damon-core-fix-unconditionally-skip-last-region +++ a/mm/damon/core.c @@ -2342,36 +2342,39 @@ static bool damos_skip_charged_region(st { struct damos_quota *quota = &s->quota; unsigned long sz_to_skip; + bool skip = false; /* Skip previously charged regions */ if (quota->charge_target_from) { if (t != quota->charge_target_from) return true; - if (r == damon_last_region(t)) { - quota->charge_target_from = NULL; - quota->charge_addr_from = 0; - return true; - } if (quota->charge_addr_from && - r->ar.end <= quota->charge_addr_from) - return true; + r->ar.end <= quota->charge_addr_from) { + skip = true; + goto out; + } if (quota->charge_addr_from && r->ar.start < quota->charge_addr_from) { sz_to_skip = ALIGN_DOWN(quota->charge_addr_from - r->ar.start, min_region_sz); if (!sz_to_skip) { - if (damon_sz_region(r) <= min_region_sz) - return true; + if (damon_sz_region(r) <= min_region_sz) { + skip = true; + goto out; + } sz_to_skip = min_region_sz; } damon_split_region_at(t, r, sz_to_skip); - return true; + skip = true; } + } +out: + if (r == damon_last_region(t)) { quota->charge_target_from = NULL; quota->charge_addr_from = 0; } - return false; + return skip; } static void damos_update_stat(struct damos *s, _ Patches currently in -mm which might be from aethernet65535@gmail.com are mm-damon-core-allow-esz-to-be-set-to-zero.patch mm-damon-core-fix-unconditionally-skip-last-region.patch docs-mm-damon-design-accurate-semantics-of-nr_snapshots.patch docs-mm-damon-design-difference-between-watermarks-and-nr_snapshots.patch docs-mm-damon-design-fix-typo-of-max_nr_snapshots.patch