From nobody Tue Feb 10 15:44:47 2026 Received: from mail-pl1-f178.google.com (mail-pl1-f178.google.com [209.85.214.178]) (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 7DFB026562C for ; Fri, 11 Apr 2025 18:31:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744396288; cv=none; b=N0N0I35cfVrnIfMnlaA59emBAoEtLpFaRgf1f3V/kk8c2hr3MMX2iIlDd2apGMNrDo96lpwKNugtuzCHsuxKu4nAH7l7Cv3ewWCQnSS66lk5IdCCG6HakHRshyIJ/V3eyyhR7x+OTD1fEkYGJPXlbyRMiKo5QdLT8ndC+uZaoS8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744396288; c=relaxed/simple; bh=nRJoE6GPpPEYF1ZSMzbifkzsjXmQmkdTAVt6VGbu/K8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GAaobFjPNDuAcyn8Bb9FyDqBwatApyIGw3VKOlcg9/4NM2TOywMZaU/yFRhCxl6aeo1Wm9gg7MEKHoc18P8PiNwZdCraAuWHen7z+aaBUfgumK1QXcYUdxZNA3z+secrB1rkaM9U7L/y88KXC2V9b8FDnX7CHYt3sdSSugzBDw4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=kNkmhTNd; arc=none smtp.client-ip=209.85.214.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="kNkmhTNd" Received: by mail-pl1-f178.google.com with SMTP id d9443c01a7336-227d6b530d8so24609895ad.3 for ; Fri, 11 Apr 2025 11:31:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1744396286; x=1745001086; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=wRPOZVQkXRfwpOzWiufgGcFpts9ZagQT6/vUKl6a6JQ=; b=kNkmhTNdgzRH3IpIlTXrLDulu6IvnZOA6VFVm5L/w9nAX+S4uBt/Hc+5uz8aWy2y/+ 0Sc/fO6K4d19RuP3qXXbY+lRFII58/ZteSX1tmhRNA73sHE+w7t24d9/HnILPcqTnn5Z gWfifrB+m7slE8eOM4DfpmE8AXjsCtvKbX2tD4hnVAlGIkXCCrCCm7O201fxA4Y7j5UY RYJiZPnienybwkKlNwZoESVniuevXqocE42z7f9mbdum9yIQegoQEHWH5luvXAcMs4Jj 1GbAIDjJ8OTC9GVQ8tin1ZMxDPGkJprwLSkGEbK2m+kMsODRWXOaURmr9eBL6tTOPton I00g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744396286; x=1745001086; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=wRPOZVQkXRfwpOzWiufgGcFpts9ZagQT6/vUKl6a6JQ=; b=rOVT7T4E6gPDdwHNHJX6icrwCZf+z3RfYK6c5b6LW8ySnXNfA1bJmJAniVrpwxATDu RmzQ7uwgHtkGz9N6W8oGmymy3R4pN60ik2IN1BG0kcTSqqbNz6X3Dou0j8grtxZYCIa2 fHYjdaKHTSrhclKpEnP0h3nvMZkm/F0wOYptQVesF3u9hI1bhK00dz59XwOOEutrEebZ dwsPHFM2S4Lqn3g6kyehM9rycv1czf8QPRHd97ZZEAnIONX9ITnJCj2aewMg4/APIm4M G1lknhcj7a9k+LS9aAYKdB2cIFtIpAwXQ0u5kwfZzQm3PtQp7jBvFudDRR1YxK/fJLX+ zN/w== X-Forwarded-Encrypted: i=1; AJvYcCXW9sdvCOlMRBomfMdzbMa2dqAQalsiEmZryMM5zWIcwPrJINaXyluNAA3NN8f49rO3yGVJUm/BpDJPy/w=@vger.kernel.org X-Gm-Message-State: AOJu0Yz9RcLqgUUQ6YeOQmMFYGIZutC0kPFSrTDY0zWUq9x3dYmCw+Pm kyivu+tWxrdPwJmxh4M9zkSZEGL/bW0om+eeHyRnyFTUHr3vXHpN X-Gm-Gg: ASbGncu7Y4EfvGfSd+oBV6oPFnc0hMmyJLKZLF5IboYF/FT9xeOOmbwdisLNbN4ytqB xYd8EgMoCqZp6nUdcDt1W6p11lH8h56Bc0UPFK9rtft3cFFQ6sVtG6/CjBG/93xFCBfICZibBCR XG/JKHj9IoNPuBq/QprQzXr1p0mDRm3TVP12KiydFgKzFZXIEiMlEIBcQxQ5bLcZgHmJXxSVUwz AWAghn+MWyBosOoa/d0E8+OPhZ83RoTJEem6pwHHcb2yMH5I6tK/LCaqsAnbKI/W5bgf8ZEEwd/ ruywDJSSaYpI18wo/xMeVvIL/7Bk3Jd7hMsDaEoRLaf0j6qwl8RSWgYEvZfFHQ== X-Google-Smtp-Source: AGHT+IEoSrwlrS+Sz3T5BanproigWZk053l8qmemLfFnl6ehs4v76G76glvJ2LAeLWGifi873TEcCg== X-Received: by 2002:a17:903:3204:b0:223:5124:a16e with SMTP id d9443c01a7336-22bea49521dmr59481775ad.5.1744396285599; Fri, 11 Apr 2025 11:31:25 -0700 (PDT) Received: from VM-16-38-fedora.. ([43.135.149.86]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22ac7c95cdcsm53279515ad.118.2025.04.11.11.31.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Apr 2025 11:31:25 -0700 (PDT) From: alexjlzheng@gmail.com X-Google-Original-From: alexjlzheng@tencent.com To: gregkh@linuxfoundation.org, tj@kernel.org Cc: alexjlzheng@tencent.com, linux-kernel@vger.kernel.org Subject: [PATCH kernfs 2/3] kernfs: switch global kernfs_rename_lock to per-fs lock Date: Sat, 12 Apr 2025 02:31:08 +0800 Message-ID: <20250411183109.6334-3-alexjlzheng@tencent.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250411183109.6334-1-alexjlzheng@tencent.com> References: <20250411183109.6334-1-alexjlzheng@tencent.com> 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 Content-Type: text/plain; charset="utf-8" From: Jinliang Zheng The kernfs implementation has big lock granularity(kernfs_rename_lock) so every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the lock. This patch switches the global kernfs_rename_lock to per-fs lock, which put the rwlock into kernfs_root. Signed-off-by: Jinliang Zheng Acked-by: Tejun Heo --- fs/kernfs/dir.c | 14 ++++++++------ fs/kernfs/kernfs-internal.h | 15 +++++++++++---- 2 files changed, 19 insertions(+), 10 deletions(-) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 355d943ffe27..d63a96786c9b 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -17,7 +17,6 @@ =20 #include "kernfs-internal.h" =20 -DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->name */ /* * Don't use rename_lock to piggy back on pr_cont_buf. We don't want to * call pr_cont() while holding rename_lock. Because sometimes pr_cont() @@ -228,7 +227,7 @@ int kernfs_path_from_node(struct kernfs_node *to, struc= t kernfs_node *from, if (to) { root =3D kernfs_root(to); if (!(root->flags & KERNFS_ROOT_INVARIANT_PARENT)) { - guard(read_lock_irqsave)(&kernfs_rename_lock); + guard(read_lock_irqsave)(&root->kernfs_rename_lock); return kernfs_path_from_node_locked(to, from, buf, buflen); } } @@ -295,12 +294,14 @@ void pr_cont_kernfs_path(struct kernfs_node *kn) struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn) { struct kernfs_node *parent; + struct kernfs_root *root; unsigned long flags; =20 - read_lock_irqsave(&kernfs_rename_lock, flags); + root =3D kernfs_root(kn); + read_lock_irqsave(&root->kernfs_rename_lock, flags); parent =3D kernfs_parent(kn); kernfs_get(parent); - read_unlock_irqrestore(&kernfs_rename_lock, flags); + read_unlock_irqrestore(&root->kernfs_rename_lock, flags); =20 return parent; } @@ -993,6 +994,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_sy= scall_ops *scops, init_rwsem(&root->kernfs_iattr_rwsem); init_rwsem(&root->kernfs_supers_rwsem); INIT_LIST_HEAD(&root->supers); + rwlock_init(&root->kernfs_rename_lock); =20 /* * On 64bit ino setups, id is ino. On 32bit, low 32bits are ino. @@ -1789,7 +1791,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct k= ernfs_node *new_parent, /* rename_lock protects ->parent accessors */ if (old_parent !=3D new_parent) { kernfs_get(new_parent); - write_lock_irq(&kernfs_rename_lock); + write_lock_irq(&root->kernfs_rename_lock); =20 rcu_assign_pointer(kn->__parent, new_parent); =20 @@ -1797,7 +1799,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct k= ernfs_node *new_parent, if (new_name) rcu_assign_pointer(kn->name, new_name); =20 - write_unlock_irq(&kernfs_rename_lock); + write_unlock_irq(&root->kernfs_rename_lock); kernfs_put(old_parent); } else { /* name assignment is RCU protected, parent is the same */ diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index 24e9514565ac..6061b6f70d2a 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -19,8 +19,6 @@ #include #include =20 -extern rwlock_t kernfs_rename_lock; - struct kernfs_iattrs { kuid_t ia_uid; kgid_t ia_gid; @@ -53,6 +51,9 @@ struct kernfs_root { struct rw_semaphore kernfs_iattr_rwsem; struct rw_semaphore kernfs_supers_rwsem; =20 + /* kn->parent and kn->name */ + rwlock_t kernfs_rename_lock; + struct rcu_head rcu; }; =20 @@ -108,6 +109,11 @@ static inline bool kernfs_root_is_locked(const struct = kernfs_node *kn) return lockdep_is_held(&kernfs_root(kn)->kernfs_rwsem); } =20 +static inline bool kernfs_rename_is_locked(const struct kernfs_node *kn) +{ + return lockdep_is_held(&kernfs_root(kn)->kernfs_rename_lock); +} + static inline const char *kernfs_rcu_name(const struct kernfs_node *kn) { return rcu_dereference_check(kn->name, kernfs_root_is_locked(kn)); @@ -118,14 +124,15 @@ static inline struct kernfs_node *kernfs_parent(const= struct kernfs_node *kn) /* * The kernfs_node::__parent remains valid within a RCU section. The kn * can be reparented (and renamed) which changes the entry. This can be - * avoided by locking kernfs_root::kernfs_rwsem or kernfs_rename_lock. + * avoided by locking kernfs_root::kernfs_rwsem or + * kernfs_root::kernfs_rename_lock. * Both locks can be used to obtain a reference on __parent. Once the * reference count reaches 0 then the node is about to be freed * and can not be renamed (or become a different parent) anymore. */ return rcu_dereference_check(kn->__parent, kernfs_root_is_locked(kn) || - lockdep_is_held(&kernfs_rename_lock) || + kernfs_rename_is_locked(kn) || !atomic_read(&kn->count)); } =20 --=20 2.48.1