From nobody Fri Dec 19 18:59:30 2025 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) (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 B3A0D28466B for ; Tue, 15 Apr 2025 15:37:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.177 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744731427; cv=none; b=aSfHET3xJsjuf0ZtPnfcWWDc6PQQqObVLm5XQEQ0GX19F4fngwZq1hQ7LiyAdL61XWk+tER4yCXbcIwlAI+0D8rZD1r1hhLPzKjaTk52BUEe6UctMuoVed0pfacUY1sji5TmhGUa8us3zTi8E6IpiNejHW5X1zLB1X+23EEWN8A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744731427; c=relaxed/simple; bh=Z0VDKI+lyzxqbYKLqxgloNLEeCjMa2vB+GmQsxeG0i8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Q3kbUtD6pvm6WNUEP3u9siGe7U6BamW7QrFTlqzww/DobtxDKdY3YROqZRtE8CraHPeGYOAYifM0/WrtzrGasU5s1WSVo14kKL9oqiteXXJGuUVpvbCip0GrSAtNvrEnudx1uD3FBE5vrvSp8Tl0PkEnGAnR8whOLE4bLZFXPmo= 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=BBdAsaLh; arc=none smtp.client-ip=209.85.214.177 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="BBdAsaLh" Received: by mail-pl1-f177.google.com with SMTP id d9443c01a7336-22435603572so54723535ad.1 for ; Tue, 15 Apr 2025 08:37:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1744731425; x=1745336225; 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=ZYqxO4DprOCfNzQ/7WnXe1FCwCF9stbfd3UHJM/ZoxE=; b=BBdAsaLh2SCYPA1hyF9X2cHF7DNCDBUxSYrzCD9aAPyauvssEJuaabY2VApk8vZlkj RNH4cKn6C+oAfmvKcHJlCOgxvxPFbIMIRpxKTb3/PSPqdCb7b/tVt5s287MwB34oV0KM czWBCUcC8LoAkSlW4IWWAmx+xs54sHUD427K+G004MqyGWjWg4i+6vF0VASLYTdxgmA0 8CGiGk4K6+dnm/LFgAtufPFInmFnKo60JCAL/5UVxjitBM4lHV6wZB0hLbJwHj5ktQ1w 3UMk79ztmw1mDOOVvR8qWU21PXrJHyTX7kt13P0YFFJpzxKoRphTeAU2XXiglWZ1JG0Z 0H9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744731425; x=1745336225; 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=ZYqxO4DprOCfNzQ/7WnXe1FCwCF9stbfd3UHJM/ZoxE=; b=SNWen9rwytQyHQJOkFGNJk+WZuC7U7xIuJAXtR9HnOnsors+IbZjIF7NO79GSLNa5V o2HZIMeojwjmRpOZrpM+U0r6z8Rfd/hAtG10xnpOWeJlM82iEPXbCMIcAzKMH+ul77W0 Ktttq1lBOclFbZmmHtNh4MrXs/PmjHOjBF21UZkOrKtuVVmfu8nY1qo6swDzfTdeOs7S VYAHBa/9OYVnJ2fq7EYV+DW/RUCVndpH7wniQ2E1yg5H9nFVcz9czgDUIuhb2TAGaRH8 UMfp+bmCd5oZXDIXNnG40k/ZVIwVRUFhD16fTzYxaq3HyGPjbjX5AiK0ndUT89YdAShq hfSg== X-Gm-Message-State: AOJu0YwDsnj8S9HDSPyGTG0d4QUTzGUII74WtrKqKFjs/D9J/YxCQFeE kUVMNv4iscCgt8OyGaSpWQMX3UCgYoBMlPBvl+UxIrWm3JOVCwC7 X-Gm-Gg: ASbGncudGLm0cptObcAZ2RDlZRwtDbJOA83gMXKkkIQRKESFMu09ToeRtWWZ4H6+URP upZ7mmj6eZNlC/RMZmFh1L/xXPSNFeGBFZbAtaCDsrp8zKO2JGQO3ZUbiWY352T3lSbAyslLhSi kpv3etHHCnIkXIfIx2toyjnMKZFy3zfyGlZsWuHqeX/lHVtsj+N2skTZX3EnNRGnDFlfcWqf61T mSg6dazz2BtqltIaWTlG6rh96VVxJHICIxu7HiQRBzgjJuTKJgmfxTG+HsgozrO5FStgzyniEMG EIJ9AbGE3t6dRGeZUQzKh6sEcdJpnUv0CE7VMmRsLjKG3PsQvYk= X-Google-Smtp-Source: AGHT+IHk23Xg0bkFNAcL5lltLUZmK04teJ4c6wBeaaL+Yj5dOcGvpscJT2psIOxUgWE4zgoj9kDBzw== X-Received: by 2002:a17:903:1447:b0:223:5c33:56a2 with SMTP id d9443c01a7336-22bea4bd57fmr280275475ad.28.1744731424875; Tue, 15 Apr 2025 08:37:04 -0700 (PDT) Received: from VM-16-38-fedora.. ([43.135.149.86]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22ac7ccca66sm119207245ad.252.2025.04.15.08.37.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Apr 2025 08:37:04 -0700 (PDT) From: alexjlzheng@gmail.com X-Google-Original-From: alexjlzheng@tencent.com To: gregkh@linuxfoundation.org, tj@kernel.org Cc: linux-kernel@vger.kernel.org, Jinliang Zheng Subject: [PATCH v2 1/2] kernfs: switch global kernfs_idr_lock to per-fs lock Date: Tue, 15 Apr 2025 23:36:58 +0800 Message-ID: <20250415153659.14950-2-alexjlzheng@tencent.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250415153659.14950-1-alexjlzheng@tencent.com> References: <20250415153659.14950-1-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_idr_lock) so every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the lock. This patch switches the global kernfs_idr_lock to per-fs lock, which put the spinlock into kernfs_root. Signed-off-by: Jinliang Zheng --- fs/kernfs/dir.c | 14 +++++++------- fs/kernfs/kernfs-internal.h | 1 + 2 files changed, 8 insertions(+), 7 deletions(-) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index fc70d72c3fe8..355d943ffe27 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -27,7 +27,6 @@ DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->na= me */ */ static DEFINE_SPINLOCK(kernfs_pr_cont_lock); static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by pr_cont_lock */ -static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */ =20 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb) =20 @@ -584,9 +583,9 @@ void kernfs_put(struct kernfs_node *kn) if (kernfs_type(kn) =3D=3D KERNFS_LINK) kernfs_put(kn->symlink.target_kn); =20 - spin_lock(&kernfs_idr_lock); + spin_lock(&root->kernfs_idr_lock); idr_remove(&root->ino_idr, (u32)kernfs_ino(kn)); - spin_unlock(&kernfs_idr_lock); + spin_unlock(&root->kernfs_idr_lock); =20 call_rcu(&kn->rcu, kernfs_free_rcu); =20 @@ -639,13 +638,13 @@ static struct kernfs_node *__kernfs_new_node(struct k= ernfs_root *root, goto err_out1; =20 idr_preload(GFP_KERNEL); - spin_lock(&kernfs_idr_lock); + spin_lock(&root->kernfs_idr_lock); ret =3D idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC); if (ret >=3D 0 && ret < root->last_id_lowbits) root->id_highbits++; id_highbits =3D root->id_highbits; root->last_id_lowbits =3D ret; - spin_unlock(&kernfs_idr_lock); + spin_unlock(&root->kernfs_idr_lock); idr_preload_end(); if (ret < 0) goto err_out2; @@ -681,9 +680,9 @@ static struct kernfs_node *__kernfs_new_node(struct ker= nfs_root *root, return kn; =20 err_out3: - spin_lock(&kernfs_idr_lock); + spin_lock(&root->kernfs_idr_lock); idr_remove(&root->ino_idr, (u32)kernfs_ino(kn)); - spin_unlock(&kernfs_idr_lock); + spin_unlock(&root->kernfs_idr_lock); err_out2: kmem_cache_free(kernfs_node_cache, kn); err_out1: @@ -989,6 +988,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_sy= scall_ops *scops, return ERR_PTR(-ENOMEM); =20 idr_init(&root->ino_idr); + spin_lock_init(&root->kernfs_idr_lock); init_rwsem(&root->kernfs_rwsem); init_rwsem(&root->kernfs_iattr_rwsem); init_rwsem(&root->kernfs_supers_rwsem); diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index 40a2a9cd819d..24e9514565ac 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -40,6 +40,7 @@ struct kernfs_root { =20 /* private fields, do not use outside kernfs proper */ struct idr ino_idr; + spinlock_t kernfs_idr_lock; /* root->ino_idr */ u32 last_id_lowbits; u32 id_highbits; struct kernfs_syscall_ops *syscall_ops; --=20 2.49.0 From nobody Fri Dec 19 18:59:30 2025 Received: from mail-pg1-f178.google.com (mail-pg1-f178.google.com [209.85.215.178]) (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 D18CC297A6B for ; Tue, 15 Apr 2025 15:37:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744731429; cv=none; b=VWQLzzFpGp9j2RLMbyaLUT0JpsxAbw4nk0Lj+Y19qA5Iog5nfY1tQMfOlGVFZI8jS5I3JmX+vT0+xJ5X64TmP1R/pWzGfXDK28sG0rJbFfnFaPhohURu9mwMJga32B5O+s9BrAnhE6vTRwveVFMYhMjp1arhjB07cbwBKPDxbO0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744731429; c=relaxed/simple; bh=BE6iCfEvSpQeaecQahBr12PQ583xoY+peR0LKYWTfeE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ALXuGQJTb+BKWjqsysW5kV3+AAQ4+4mShxhw5JJEoMMfqA31EG7CYrl31aG23e7EQQwOW66w/jD08jefFaH2JQ8JrnJqbPys7PuWaztCtY65p0seK/Gt8x5IAgfo22iiyE7kfGwBOt3qh0DmNz65YYfKqG28Xd67vaMEXL+KoWs= 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=gtSvAtV5; arc=none smtp.client-ip=209.85.215.178 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="gtSvAtV5" Received: by mail-pg1-f178.google.com with SMTP id 41be03b00d2f7-af91fc1fa90so5276511a12.0 for ; Tue, 15 Apr 2025 08:37:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1744731427; x=1745336227; 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=8wjKFHFGgl+ccUq19hljlXknKY9MIrLWp5vcuR4YkYY=; b=gtSvAtV5Tkna6QyXly6XnPI9R+lhl5FzX6c1PsVaHAk8mZtuR0ZdHgtXkJAcnx1+xl D68c2V0SuVV8vWZg5SE0u23WPbp9W3ntENW4YKbt/9qUuAQ6bLRvPyVdbO0UQ5YhYVko vqP4RGlfk4mPewAwyHqB/6MBjXltwO6HI+IvNiYAvVmMIxcrZtIdlqkqiY9xlCDoz2RQ GPiCcSZ7PeW0BJLgMAHoqrUS4X36tIFIdOCwtu/qtaTFjqFwZ3X/WJm8xAdcJXNMFbRO eBq/LDt+hlaD1fD1o43KlQ+0zywyILcC5LolJT/xA+5BTFRyu0CzG3ftPpB6l/0WVB3/ +eEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744731427; x=1745336227; 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=8wjKFHFGgl+ccUq19hljlXknKY9MIrLWp5vcuR4YkYY=; b=S9eT1L4G4pbSjGEkwMAM4yP3xEuINJhzwx+jdLqQN99ZU2m5P9XYKNf10ZiP3IK66T QqpyMkzxa4UMJN0r0VlyKT9gRwV8DZqSL7NLze2uQJuOF1K6A4Nw3RNqeBgMXFdZhNZQ wtAt22v4z/3OAMNAtS61511Cw6aUH2qK02BKYTRjKLExvJGgjJIsVvpjl3P0Rfe9RA3w hRtZSYEMF/MchPxVZ0vwZ6813gSqnzPZzs7uDujrdy3VQ5AvlGZbJa/UFvuU+llU4JgH 4aBO+Oj0fzBTlPL737vtLllPyKaVqnsuYDbrUq4rFBk38SeiljuRozkclOlEM9xRpHMg Nf5g== X-Gm-Message-State: AOJu0YwkcLoI7k2uY77e0vnoGMo++8Jn5/Qz2D77PpvBIx8yE7MkkcaL u1k0h0jbiIszqsMfioJSqKwLZdXPsLp6ZpsTAQA+K8WHZ5TZi2RZvhwyXNbX X-Gm-Gg: ASbGncsIrdTFBcM+lthdDjlAJ+2rPqOShieHq1AiaYcm/pUYSGh0xZewGdehL1ztni9 Gfpqo0YqamR1PNvXy5mp+I7xTje/dVqBrjdqrGrhfRHv4kbK+hHiIzzAbVd7kryMOpU63XaMzxl F6KmS0VlJ8kd5tA+/MQxdcMsEe6hdWtfTqvSbofxUckDbBqvkOI5IjNICwSpXZe0PB4QMd2beJq ovjKqMaQq0z5N564r3KZDYowBkN8IZ4FmO5+IpI/hIcoSIOp43/7mEHWIDg1ajvA/I0TEonesV5 jGpG7hzQAwMbqBvaT8dxS6jnva30y1Ea6hWe6xQWil6T85VBKaI= X-Google-Smtp-Source: AGHT+IFwf6Q5iuXr+ewJJ9cHDVmT2feV8opagy2M4ZP7xuc88bPyM/k9Jy/tADoVDPK0uZnPfCZvBw== X-Received: by 2002:a17:90b:35c5:b0:2fe:ba82:ca5 with SMTP id 98e67ed59e1d1-308236343efmr27443251a91.11.1744731426832; Tue, 15 Apr 2025 08:37:06 -0700 (PDT) Received: from VM-16-38-fedora.. ([43.135.149.86]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22ac7ccca66sm119207245ad.252.2025.04.15.08.37.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Apr 2025 08:37:06 -0700 (PDT) From: alexjlzheng@gmail.com X-Google-Original-From: alexjlzheng@tencent.com To: gregkh@linuxfoundation.org, tj@kernel.org Cc: linux-kernel@vger.kernel.org, Jinliang Zheng Subject: [PATCH v2 2/2] kernfs: switch global kernfs_rename_lock to per-fs lock Date: Tue, 15 Apr 2025 23:36:59 +0800 Message-ID: <20250415153659.14950-3-alexjlzheng@tencent.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250415153659.14950-1-alexjlzheng@tencent.com> References: <20250415153659.14950-1-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 --- 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 2.49.0