From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794480910; b=Sfbctibf7Bu3KFjq/0xcHRa9t2ytits5tS/98APeIoIFgPbj8siXRCG4NrEmQi+nft2U Peg6SkApyaX9qSGomFzV07FGBv4JuEAgvYU76T/SMxUjCMpyejpRAVMs0/HwACxUqIs9t SjdmWKyGEag7Tobk/0y/6rh8SUmlTeXoyqxN13Z2QD3B3OAhNcG/i2S4NJBKilIvyscQq aUtP+3A27TiPkCdEgpzD0U+YKBFnlmgix1EEY9GK7FVTXn562Z4EzO4+o2F0iGDUI1uxz d5lbLZFNsHYGPs9janARyJdVl+NbkkDj0TlaggEQ9UZCnVKKbB/pK8KZvNyknfGNxVA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794480910; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:Content-Language:To:Cc:References:From:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=hBBRka0fgdENvERIYsPzoLXmI7OdvHBhAV6rADe9TMQ=; b=tdXMhfCbSTjVbWC4IiKGpjczM5bDZftdwYA+lNNZxCQIB8iX+C6BOlR67eMz5Mwmva69 W/1B7HGBFOuxxvnxC2UfmLuFYItxxTmwKGhNfaDckvQsv2tfJ7DhuhYqWzzpVhnEx0MBn f029wXa/r4sjXwknYUCLx8XRkz4Cv+lkKs+K63oy9hyHMbUNijF874RPEKIp0Y9mxFEat 0txDrCvvBFwBzS4yfnzsb/4LiqOwJNpF1WE40o5ysP2ue57deAvdQMmzyB9PG1uK5nQ0I 1Ya7M4HIRrCfIZ4SA/WI53Rkr4S1GlhGSDXddFBLeeVGkCrn5JlJMZ8TsoAvrfUL/sw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=mVR6HgOg; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 826B8606A323; Thu, 12 Nov 2026 10:55:10 +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=mVR6HgOg Received: by smtp.kernel.org (Postfix) with ESMTPSA id 735FB1F00A05; Thu, 12 Nov 2026 10:55:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794480910; bh=hBBRka0fgdENvERIYsPzoLXmI7OdvHBhAV6rADe9TMQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=mVR6HgOg/ceImyZhmMvUyCD1gCi9KdMcx9kDP6BtyYopaWHif25AK0lFQXIz3PlLm zvj/wn+r8mOdfmobgmEkg1F5syvIhoNuPdQ0wq/7Bt4XHmUBfShWInqaA3hMM0qgAk bCf+ouF4iY6V9bVOC1ovlXEnT7k/BLwoWZoFLHA9hnQ8Yln0CfvmEvcWw3Uhd4/CQL R3wgbLkxrrOeBi8R+QVPPIlQ6OpYmhYd7Z2hIKu7PV5KakhWIHd6htoTsjaYROEZP6 1fsO3oSdzbA9kWGhJD8pLIphaoAQSehJAY1gwsvr18zimH2uEhz1LPhYVDHRsm92/Y ddIb4UYpAYEUg== Message-ID: <9d1fa2c1-7090-417f-adfc-0b128c37622e@kernel.org> Date: Thu, 12 Nov 2026 11:55:05 +0100 X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] memcg: flush nr_charged_bytes when the obj stock trylock fails Content-Language: en-US To: Shakeel Butt , Andrew Morton Cc: Johannes Weiner , David Hildenbrand , Michal Hocko , Roman Gushchin , Muchun Song , Meta kernel team , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , stable@vger.kernel.org References: <20261112013220.4064478-1-shakeel.butt@linux.dev> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20261112013220.4064478-1-shakeel.butt@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/12/26 02:32, Shakeel Butt wrote: > When interrupt code, such as an RCU callback in softirq, runs on top of > a task that holds the obj stock lock, its trylock fails and the bytes go > to objcg->nr_charged_bytes. Nothing empties that counter while every CPU > using the objcg keeps it in its stock, so it can grow without limit. > > Users see memory.current and the "kernel" field of memory.stat keep > growing while the cgroup's real usage does not. With memory.high or > memory.max set, the cgroup is reclaimed, throttled or even OOM-killed > for memory it does not use. The counter is 32-bit, so after 4 GiB it > wraps, and those 4 GiB stay charged to the cgroup and its ancestors > until reboot, even after the cgroup is removed. > > Fix it by uncharging the whole pages in nr_charged_bytes whenever the > trylock fails. > > Fixes: 200577f69f29 ("memcg: objcg stock trylock without irq disabling") > Reported-by: Chris Mason > Signed-off-by: Shakeel Butt > Cc: stable@vger.kernel.org Acked-by: Vlastimil Babka (SUSE) > --- > mm/memcontrol.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index f5f567f7d4a9..091401cecf39 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3553,6 +3553,8 @@ static void __refill_obj_stock(struct obj_cgroup *objcg, > int i, slot = -1, empty_slot = -1; > > if (!stock) { > + nr_bytes += atomic_read(&objcg->nr_charged_bytes) > + ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0; > nr_pages = nr_bytes >> PAGE_SHIFT; > nr_bytes = nr_bytes & (PAGE_SIZE - 1); > atomic_add(nr_bytes, &objcg->nr_charged_bytes);