From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-151.mta1.migadu.com [95.215.58.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D5DD037996B for ; Mon, 31 Aug 2026 02:28:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.151 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788143304; cv=none; b=XoDZcx47+QtPSGL4N4UWxaVrJrxKQ62kN9cvFUMsDHjND7n4CGsKHc1SZAixlKmr2YbjrqhyHQ1iASkMEmrtXUXj53YLe1o3NXZGjDfMN6PfjF5f/S0AnzLQ8ZBAHOTnZjrS+I0Yn/+vnqZz+cvd9GEIeHBl4Im3LNJRHglnWoM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788143304; c=relaxed/simple; bh=FlD54LcSt+NZlq7D9GrYKYXHGNdn1dwZ5TEhIQvteAM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iE/FCA+ei/nAe9CzYucFlraQryCY76OMd4vPs6s/h5Kbl2UVrhDnBhln8Zbc/Bo+7bP4S9dnt0IJOYcJs770CzfsUKvNDSKoWRBAgIDgNpKoDWu6vYrvFgsOaxoWR01GBZWKFUoxk4jhXa9UNYqCW9HTxieVXym9eX/wJrk7nIU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=bmStEd8N; arc=none smtp.client-ip=95.215.58.151 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="bmStEd8N" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=FlD54LcSt+NZlq7D9GrYKYXHGNdn1dwZ5TEhIQvteAM=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788143294; v=1; x=1788748094; b=bmStEd8NE/ucj4J8M/w/Y6phdgdh1G91NbqqAuoOfNin/BTsO66DH11e5Eu90l5uX/o++Kn2 K8Bu1EBL85QOTc/4vWaSKmkJL+TyYH0TKv1dEYXNDVfAZujROnkhNiNvW9Ofm7XMeA4TZLYRfMH M7VRss+YhUnkaEAslP71jR00= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 5a4496ccf4f994c7; Mon, 31 Aug 2026 02:28:03 +0000 X-Mizu-Trace-ID: 5a4496ccf4f994c7 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Mon, 31 Aug 2026 10:28:00 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/4] fs: fix missed removal of super_fs_objects_eligible() To: Andrew Morton Cc: hughd@google.com, baolin.wang@linux.alibaba.com, usama.arif@linux.dev, brauner@kernel.org, david@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng References: <3b038d373c70ebac7cdabfb0035bb91d1d6e6cfe.1786955972.git.zhengqi.arch@bytedance.com> <20260828114129.909edbfb7e42b36af2da6a98@linux-foundation.org> <20260829162350.1ee9e17d71a297b06b171941@linux-foundation.org> From: Qi Zheng In-Reply-To: <20260829162350.1ee9e17d71a297b06b171941@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Andrew, On 8/30/26 7:23 AM, Andrew Morton wrote: > On Sat, 29 Aug 2026 09:49:44 +0800 Qi Zheng wrote: > >> Hi Andrew, >> >> On 8/29/26 2:41 AM, Andrew Morton wrote: >>> On Mon, 17 Aug 2026 17:03:25 +0800 Qi Zheng wrote: >>> >>>> From: Qi Zheng >>>> >>>> Commit 0ef8faff490be ("fs: push nr_cached_objects memcg gating into >>>> individual filesystems") forgot to drop the super_fs_objects_eligible(), >>>> just fix it. >>> >>> Oh. Why? Please can we have a description of what's wrong with the >>> current code? >> >> As I replied in another thread [1], this fix and commit 0ef8faff490be >> together make up the complete patch originally sent by Usama [2], so >> they should be squashed together. > > 0ef8faff490be is upstream so they can't be squashed! So sad. > >> Without this fix, all memcg-aware >> nr_cached_objects() will be skipped during memcg-level shrinking. >> Besides the newly added memcg-aware shmem huge shrinker, XFS will also >> run into issues. > > OK, please add this info to this patch's changelog. Please also decide > whether a cc:stable should be added and if so, ensure the changelog > makes clear why we're recommending a backport. > > As part of this, let's expand on "XFS will also run into issues". How about this instead: --- Commit 0ef8faff490be ("fs: push nr_cached_objects memcg gating into individual filesystems") was meant to drop the blanket memcg gate in fs/super.c and let each ->nr_cached_objects() implementation decide for itself whether it is meaningful in per-memcg reclaim. However, when that patch was applied the removal of super_fs_objects_eligible() and its two call sites in super_cache_scan() / super_cache_count() was lost, so the helper is still gating every ->nr_cached_objects() hook and 0ef8faff490be is effectively a no-op. Consequences of the leftover gate: - XFS's inode-reclaim hook, which is intentionally driven from per-memcg contexts to free memcg-charged slab, is still short-circuited in fs/super.c — exactly the regression from commit 0baad6f9b997 ("fs/super: skip non-memcg-aware nr_cached_objects in memcg slab shrink") that 0ef8faff490be was written to undo. Memcg-charged XFS inode slab therefore keeps piling up under per-memcg pressure until global reclaim kicks in. - Any future ->nr_cached_objects()/->free_cached_objects() that grows memcg awareness is likewise blocked before it can run, so filesystems cannot opt in to per-memcg reclaim on their own — defeating the whole point of pushing the gating decision down into the callbacks. Drop the leftover helper and its call sites so the intent of 0ef8faff490be actually takes effect. Fixes: 0ef8faff490be ("fs: push nr_cached_objects memcg gating into individual filesystems") Cc: stable@vger.kernel.org --- Can you fix up the commit message directly on your end? Let me know if you prefer me to spin a v5 instead. Thank, Qi > > Thanks. >