From nobody Sun Feb 8 11:43:11 2026 Received: from out-174.mta1.migadu.com (out-174.mta1.migadu.com [95.215.58.174]) (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 3615C1A4F0F for ; Thu, 15 Aug 2024 15:54:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.174 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723737279; cv=none; b=cRm7ecvtGjnc5UXF0+zhP3wWBgyzHnNR12Qs+5X6SqAAz6CjT9PkUPhaOJGhXqAyUQJhiL9rHrFT6oB+YGrWqOLB1jvEOVQsTIzeNUqSizjotJnbYfLOI+1EXD1V8Qa1j4zQQyLOl9YzfpqvQDEihfrxtOVwTRTa+nqQ7ReqoTA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723737279; c=relaxed/simple; bh=UEuDwq5fCqw0aYSvkVR5Xz7u6/KcgixJHCd2wEmzA4Q=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=uV8INvD+XjvGF/d0GryqKuhRcFng6R90B38cT6f8lD4iyMqpIer5FjbsOtAMNEzQwrHrDWJzznzZCxoDFqdHc06ApHMfHVneIZodkMLqrFnLQ5oKrS5sRz1zZ6BnpNyuFocrA9/SMeYEbu4uMYYGtQ+SBNv2PeerWBMX3JHVw8I= 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=Kx2KlLkN; arc=none smtp.client-ip=95.215.58.174 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="Kx2KlLkN" 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=1723737275; 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=DjpAiVrd2YJQXzgNMIISiRWFMgGrAObcvytxXAsoS+o=; b=Kx2KlLkNtiaJWRRx1Lpiwnl0vG51HtNZvOmfAwA7VxHKPaUsVKh74zukXNwa6JqfNawSrb Ai6f4bTwh+vYS7bZvva9tO+v/MbyrUBhtVtoR8lGaNnb5x/BIVKBRnPamna0xBLDdeHYq7 NR3qdWieoaGRvtDMrqCvMlV6YN0AyZk= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , "T . J . Mercier" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Meta kernel team , cgroups@vger.kernel.org, Matthew Wilcox , Michal Hocko Subject: [PATCH v2] memcg: replace memcg ID idr with xarray Date: Thu, 15 Aug 2024 08:54:02 -0700 Message-ID: <20240815155402.3630804-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" At the moment memcg IDs are managed through IDR which requires external synchronization mechanisms and makes the allocation code a bit awkward. Let's switch to xarray and make the code simpler. Signed-off-by: Shakeel Butt Suggested-by: Matthew Wilcox Reviewed-by: Roman Gushchin Reviewed-by: Matthew Wilcox (Oracle) Acked-by: Johannes Weiner Reviewed-by: Muchun Song Acked-by: Michal Hocko Signed-off-by: Andrew Morton --- Changes since v1: - Fix error path in mem_cgroup_alloc (Dan Carpenter) mm/memcontrol.c | 39 ++++++++++----------------------------- 1 file changed, 10 insertions(+), 29 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index df84683a0e1c..e8e03a5e1e5e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3408,29 +3408,12 @@ static void memcg_wb_domain_size_changed(struct mem= _cgroup *memcg) */ =20 #define MEM_CGROUP_ID_MAX ((1UL << MEM_CGROUP_ID_SHIFT) - 1) -static DEFINE_IDR(mem_cgroup_idr); -static DEFINE_SPINLOCK(memcg_idr_lock); - -static int mem_cgroup_alloc_id(void) -{ - int ret; - - idr_preload(GFP_KERNEL); - spin_lock(&memcg_idr_lock); - ret =3D idr_alloc(&mem_cgroup_idr, NULL, 1, MEM_CGROUP_ID_MAX + 1, - GFP_NOWAIT); - spin_unlock(&memcg_idr_lock); - idr_preload_end(); - return ret; -} +static DEFINE_XARRAY_ALLOC1(mem_cgroup_ids); =20 static void mem_cgroup_id_remove(struct mem_cgroup *memcg) { if (memcg->id.id > 0) { - spin_lock(&memcg_idr_lock); - idr_remove(&mem_cgroup_idr, memcg->id.id); - spin_unlock(&memcg_idr_lock); - + xa_erase(&mem_cgroup_ids, memcg->id.id); memcg->id.id =3D 0; } } @@ -3465,7 +3448,7 @@ static inline void mem_cgroup_id_put(struct mem_cgrou= p *memcg) struct mem_cgroup *mem_cgroup_from_id(unsigned short id) { WARN_ON_ONCE(!rcu_read_lock_held()); - return idr_find(&mem_cgroup_idr, id); + return xa_load(&mem_cgroup_ids, id); } =20 #ifdef CONFIG_SHRINKER_DEBUG @@ -3558,17 +3541,17 @@ static struct mem_cgroup *mem_cgroup_alloc(struct m= em_cgroup *parent) struct mem_cgroup *memcg; int node, cpu; int __maybe_unused i; - long error =3D -ENOMEM; + long error; =20 memcg =3D kzalloc(struct_size(memcg, nodeinfo, nr_node_ids), GFP_KERNEL); if (!memcg) - return ERR_PTR(error); + return ERR_PTR(-ENOMEM); =20 - memcg->id.id =3D mem_cgroup_alloc_id(); - if (memcg->id.id < 0) { - error =3D memcg->id.id; + error =3D xa_alloc(&mem_cgroup_ids, &memcg->id.id, NULL, + XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL); + if (error) goto fail; - } + error =3D -ENOMEM; =20 memcg->vmstats =3D kzalloc(sizeof(struct memcg_vmstats), GFP_KERNEL_ACCOUNT); @@ -3709,9 +3692,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys= _state *css) * publish it here at the end of onlining. This matches the * regular ID destruction during offlining. */ - spin_lock(&memcg_idr_lock); - idr_replace(&mem_cgroup_idr, memcg, memcg->id.id); - spin_unlock(&memcg_idr_lock); + xa_store(&mem_cgroup_ids, memcg->id.id, memcg, GFP_KERNEL); =20 return 0; offline_kmem: --=20 2.43.5