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 76D8EC44501 for ; Tue, 14 Jul 2026 10:15:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 60EEB6B0092; Tue, 14 Jul 2026 06:15:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5714F6B0093; Tue, 14 Jul 2026 06:15:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4602C6B0095; Tue, 14 Jul 2026 06:15:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 09D436B0092 for ; Tue, 14 Jul 2026 06:15:10 -0400 (EDT) Received: from smtpin14.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 667ABA0331 for ; Tue, 14 Jul 2026 10:15:09 +0000 (UTC) X-FDA: 84986974338.14.F149F66 Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) by imf29.hostedemail.com (Postfix) with ESMTP id CF3DD12000D for ; Tue, 14 Jul 2026 10:15:07 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=o7OshBKp; spf=pass (imf29.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.173 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784024107; 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:references:dkim-signature; bh=56WaBc6KXQyiipU+GOph11PsAxOVbA6Vo71DO1epUmU=; b=Tk6ciVpRyUu9YnNbalBsxGG2uAIE25v6lpzDqlb4PQ3lGq+osz6MBQwYgh4ZH227Z6q19g 1WX8DttsP/Naptbfarq0JOAWKDKFNUcCI3amE51KLywOQsNQw+Jea9TZ7Jkba+qQaxB9k+ 6pMBuVDtemE0y7+6oJ0idsE21D86E4Y= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=o7OshBKp; spf=pass (imf29.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.173 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784024107; b=vmaAGiD+VxltXswhrya6jHA/sPwTaHw288PNW8cl49RfbECSL0U4nErOuGG82Mg2951yW7 104UOYqqBv/8e9mwFyaO8iHed5yA20sNMPK96TkC4s7WUO3X/8636VZyuOwBqdmnuFeuDr sC55aLPa3/DhGc8yc3Va32ozqBaO+wY= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784024106; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=56WaBc6KXQyiipU+GOph11PsAxOVbA6Vo71DO1epUmU=; b=o7OshBKpJ96UBIQa6AkejMkZQiPGv9LV20o8q96VoBIHxr5DI02vQGJoH6/Rms4+sbJWYo l3+EccFU9tEcAmYpRR7YTLNB6Bx69xoTQMKcDdqKvi2CC7Gh7W6W71zYW4zTaAVUEPL87x Adi41BX+7qZ8wEaW2Sx8IuXJzH1/fEM= From: Usama Arif To: brauner@kernel.org, qi.zheng@linux.dev, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro , linux-mm@kvack.org Cc: hughd@google.com, boris@bur.io, clm@fb.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, cem@kernel.org, linux-xfs@vger.kernel.org, shakeel.butt@linux.dev, hannes@cmpxchg.org, riel@surriel.com, kernel-team@meta.com, Usama Arif Subject: [PATCH] fs: push nr_cached_objects memcg gating into individual filesystems Date: Tue, 14 Jul 2026 03:14:54 -0700 Message-ID: <20260714101454.1202449-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: m4s76c5d5na77m7ohgo7tn54eeopsy1o X-Rspamd-Queue-Id: CF3DD12000D X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1784024107-381279 X-HE-Meta: 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 6UOmWawP waL7BVPxORpGeKt9FIeXAHQ6z9enCM+jxjU0NU8Lhlp1taH3568iXZdWhl4vZjLPOmNW22phRWo5ji7mWGxo+vb2b6is7gmxGw9RzMk1hP8rQwqlcjns0cDMFJwDVqK4h7OLfo/i4UHveTo2UcV+RbMysrti9dgZpMi1NrZnl8ukJZz7a23SxWrjJQHgG6on1g+4hCw0SCCoImYgPjyoE8o/Htkws/KbWPHPXIVQB2A5m1CsiJYxY/4FR/w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Commit 0baad6f9b997 ("fs/super: skip non-memcg-aware nr_cached_objects in memcg slab shrink") added a check in fs/super.c that skips the ->nr_cached_objects() hook whenever the shrinker is invoked for a non-root memcg, because none of the current implementations (btrfs, xfs, shmem huge) honour sc->memcg. That policy is really a filesystem-owned property: fs/super.c should not encode the assumption that these hooks are never memcg-aware, since a future implementation might legitimately filter by sc->memcg. Move the check into btrfs_nr_cached_objects(), xfs_fs_nr_cached_objects() and shmem_unused_huge_count() so each filesystem can lift the restriction independently once its underlying counters/scans become memcg-aware, without needing a coordinated change to fs/super.c. Behaviour is unchanged: calls into these hooks from shrink_slab_memcg() still early-return 0 for non-root memcg contexts, keeping the shrinker bit clearable in each memcg's bitmap; the global (kswapd or root direct reclaim) path still drives them as before. Signed-off-by: Usama Arif --- fs/btrfs/super.c | 11 +++++++++++ fs/super.c | 19 ++----------------- fs/xfs/xfs_super.c | 12 ++++++++++++ mm/shmem.c | 11 +++++++++++ 4 files changed, 36 insertions(+), 17 deletions(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index a7d804219bec..16c24bccc897 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include @@ -2434,6 +2435,16 @@ static long btrfs_nr_cached_objects(struct super_block *sb, struct shrink_contro struct btrfs_fs_info *fs_info = btrfs_sb(sb); const s64 nr = percpu_counter_read_positive(&fs_info->evictable_extent_maps); + /* + * The evictable extent map counter is filesystem-global and does not + * honour sc->memcg, so it is only meaningful on the global (kswapd or + * root direct reclaim) shrink path. Skip the per-memcg iterations of + * shrink_slab_memcg() to avoid queueing duplicate global work and + * pinning the shrinker bit in every memcg's bitmap. + */ + if (sc->memcg && !mem_cgroup_is_root(sc->memcg)) + return 0; + trace_btrfs_extent_map_shrinker_count(fs_info, nr); return nr; diff --git a/fs/super.c b/fs/super.c index d2d04a6f4f84..a8fd61136aaf 100644 --- a/fs/super.c +++ b/fs/super.c @@ -24,7 +24,6 @@ #include #include #include -#include #include #include #include /* for the emergency remount stuff */ @@ -170,19 +169,6 @@ static void super_wake(struct super_block *sb, unsigned int flag) wake_up_var(&sb->s_flags); } -/* - * The s_op->nr_cached_objects hooks (used for example by btrfs and xfs) - * operate on filesystem-global state and ignore sc->memcg. Driving them - * from per-memcg shrink_slab_memcg() invocations only burns CPU walking - * per-cpu counters and queueing duplicate work: the actual reclaim happens on - * the global path (kswapd or root direct reclaim) regardless. Restrict them - * to that path. - */ -static inline bool super_fs_objects_eligible(struct shrink_control *sc) -{ - return !sc->memcg || mem_cgroup_is_root(sc->memcg); -} - /* * One thing we have to be careful of with a per-sb shrinker is that we don't * drop the last active reference to the superblock from within the shrinker. @@ -212,7 +198,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink, if (!super_trylock_shared(sb)) return SHRINK_STOP; - if (sb->s_op->nr_cached_objects && super_fs_objects_eligible(sc)) + if (sb->s_op->nr_cached_objects) fs_objects = sb->s_op->nr_cached_objects(sb, sc); inodes = list_lru_shrink_count(&sb->s_inode_lru, sc); @@ -273,8 +259,7 @@ static unsigned long super_cache_count(struct shrinker *shrink, return 0; smp_rmb(); - if (sb->s_op && sb->s_op->nr_cached_objects && - super_fs_objects_eligible(sc)) + if (sb->s_op && sb->s_op->nr_cached_objects) total_objects = sb->s_op->nr_cached_objects(sb, sc); total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc); diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index eac7f9503805..f0d8251fad3b 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -54,6 +54,7 @@ #include "scrub/rcbag_btree.h" #include +#include #include #include #include @@ -1242,6 +1243,17 @@ xfs_fs_nr_cached_objects( /* Paranoia: catch incorrect calls during mount setup or teardown */ if (WARN_ON_ONCE(!sb->s_fs_info)) return 0; + + /* + * The reclaimable inode count is filesystem-global and does not honour + * sc->memcg, so it is only meaningful on the global (kswapd or root + * direct reclaim) shrink path. Skip the per-memcg iterations of + * shrink_slab_memcg() to avoid queueing duplicate global work and + * pinning the shrinker bit in every memcg's bitmap. + */ + if (sc->memcg && !mem_cgroup_is_root(sc->memcg)) + return 0; + return xfs_reclaim_inodes_count(XFS_M(sb)); } diff --git a/mm/shmem.c b/mm/shmem.c index 5789a0f5a346..3ba812e4f5ba 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -846,6 +846,17 @@ static long shmem_unused_huge_count(struct super_block *sb, struct shrink_control *sc) { struct shmem_sb_info *sbinfo = SHMEM_SB(sb); + + /* + * The per-superblock shrinklist is filesystem-global and does not + * honour sc->memcg, so it is only meaningful on the global (kswapd or + * root direct reclaim) shrink path. Skip the per-memcg iterations of + * shrink_slab_memcg() to avoid queueing duplicate global work and + * pinning the shrinker bit in every memcg's bitmap. + */ + if (sc->memcg && !mem_cgroup_is_root(sc->memcg)) + return 0; + return READ_ONCE(sbinfo->shrinklist_len); } #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ -- 2.53.0-Meta