From nobody Mon Feb 9 14:00:36 2026 Received: from mail-pl1-f171.google.com (mail-pl1-f171.google.com [209.85.214.171]) (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 7F05C263898 for ; Fri, 11 Apr 2025 18:31:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744396286; cv=none; b=RfomDKp+yEd/h9bDxeU+KWvKz70ozvAxAQFmE2Hs4h7H2rxGu/EEVnqPrc8VyIuGtIE4Y5tclpnI7VS7W2TpCVnDe6gXd0zGVRE4TqDhBomntn/o7DPbj/rKMcw5/+p22piGhLVQtKnkPNRoHm8GhqckCHTedVhheE1ecVPxElI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744396286; c=relaxed/simple; bh=vYIH9CVcwhoi0vLUkNUg59Jsq+NQkoxMiA5AdiUfit4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LzuKi2FyIBkHWNPhP0CXxgCaaTqQYqaB9qT8pBu56ZabZ97U0tis3pqYjHzv87Bqe49G1RHBLlkdO0yz0FymkPiR+hwlRWVdHjimmHUKfY+BRjGGmuMC4s9nMHzqsNPpsijULHfyZFRD0WqpkwoleGXqP1H9PO01fPPLVA2dSS0= 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=EGy7z8sR; arc=none smtp.client-ip=209.85.214.171 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="EGy7z8sR" Received: by mail-pl1-f171.google.com with SMTP id d9443c01a7336-22403cbb47fso26058135ad.0 for ; Fri, 11 Apr 2025 11:31:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1744396284; x=1745001084; 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=Ql6xemgsTeTnj5OBzjSrp7KTsy6FsJl8WG9i01Bevqo=; b=EGy7z8sRuMw/w2dz4jWzQTQUy8A5vClKWysehLzMD3dX+mPVT/Bcj8OldqocXYgEBV +aBgyWhHgsNzEJExvhPGEVEaKmTHqvbl6v3d63N3u+gVJ8rgWWknu89OL+Tg+/kzFKo6 ZLA+zqjxf0xEMd6XcP+98DIH+9Q5zdf5VoOBpZuBUsVandSQjMSy9iCxJBNn5WL7QTsu R9Ukns0bteKLseGPWsWh2fwVH3M3RdeRCA02kmk/m/Fg85MJZCBOFBAYyxVF/MGqp9B2 JfGaEsPrFQsqSFdF3pmMq0tgcO0ACwsuEIMcqRU3gWjlgj3ewxKbJ7hwZ5yO4Q02MKQ+ srvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744396284; x=1745001084; 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=Ql6xemgsTeTnj5OBzjSrp7KTsy6FsJl8WG9i01Bevqo=; b=mNkbB5SxWcuziHG7VbP72XbYs5QUH45XmCy/08WM8X7ets/rR7KAp0hJ3KYIv53FGu ndzAizRaECe5SH2Mwnlr3loLyS5gORJ1bc2j+8Q06g6zhW4l6oIOiQRJLIb8M1XPfVIv sd0rMuJzgA1dfmPQMTepkOfhvnxZWI/VQ1LP14K82Ta5UlSq1AzjQJWNuNw2ygYMjLgj Y7lwPyiSmR5CPEPs2GD9yD4DN9MlUQ0vJma5gWFk0G9j0bkeekqCGN6z1qtDA+NdSfvQ swMCZ+lt/35PW0Ija4b0ghYcyyrWy9eMlUsufv41KUKKnigeBrcWYKJOPLv0OXTtjqFP 0Dtg== X-Forwarded-Encrypted: i=1; AJvYcCUDHqa0iD54GLqpi4ckscVDm3BRCIPXgaxOiTwnRsdf9zzM4CwMK4QAJHZzRB5TWb9RUk3VyZCUbLjSxo0=@vger.kernel.org X-Gm-Message-State: AOJu0YzEic+ZVk8BJNHztmQHDGzRZe7/bNQr3gqQs0ErOiyTNjDwg554 bK1DXC/Iv70M8ZpfdsjvILaOmSxWS1UWX+1m64i5o4smnwFmIuzE X-Gm-Gg: ASbGncuaFUfs8UGft/m5sFsLeaF2XGCxCcAIcr32OxhykLMJ0fnekj1GvyxKe12TxqH vLvDf0waktsv4uXURm0ykGUtJREVCSi2DbdHfKAbe/uMKb0+erkXuYixypTQ1a9Hk15q2Re4ou4 1C/hZrrer3Ct2xBcCnDENsBIG+muJjU4x0MXENiu2Aq5EkywfFlxDetDRWM3BntJubgV7yq9l3w vYjwZPz/ToXZ9yszM0ytd6G1QS9ZBrBi3+O9vc93iMY666sIv7hWJVG/iRBLtacVTwXQzzjGRNc t8dgG4I7QCpLXgoDru643P1csjeXCjirf/ME2lIumAfmGFUcbbM= X-Google-Smtp-Source: AGHT+IEEo9h/z0kik2OsRdO8MlrRqDu0viVFKS7VlyPrm4TiRdh0ZrD6kKmbu129uRROwwkNBMLY1w== X-Received: by 2002:a17:903:3c44:b0:224:162:a3e0 with SMTP id d9443c01a7336-22bea50dfb1mr52127375ad.49.1744396283596; Fri, 11 Apr 2025 11:31:23 -0700 (PDT) Received: from VM-16-38-fedora.. ([43.135.149.86]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22ac7c95cdcsm53279515ad.118.2025.04.11.11.31.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Apr 2025 11:31:23 -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 1/3] kernfs: switch global kernfs_idr_lock to per-fs lock Date: Sat, 12 Apr 2025 02:31:07 +0800 Message-ID: <20250411183109.6334-2-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_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 Acked-by: Tejun Heo --- 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 2.48.1 From nobody Mon Feb 9 14:00:36 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 From nobody Mon Feb 9 14:00:36 2026 Received: from mail-pl1-f173.google.com (mail-pl1-f173.google.com [209.85.214.173]) (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 5BFAD266B75 for ; Fri, 11 Apr 2025 18:31:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744396289; cv=none; b=ggKMFL8//vf2YUTn2ARw3GEA0InOukw6VKdI194dB41VbmL6mebM3KVdJoT8euNJ/s/XcoLg2tHKpWGbnvMJkYe43mIlkjlM8OR+VN5wiupEeTaB3yEuqmVEbVglbD1uc1w4FHPzkBLBVMdRM/316LCqfmGSpmeI2wXH3kazdEs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744396289; c=relaxed/simple; bh=VGA/wTW21CpkRa7qBwWnyEviULB87UW6YI+tRU2IAtg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cy0sLPsWW3PqwWui4i7mAaeqQHJ2om4JCf5aaSURahwisA6//UMWGPT5BHz2XY+1qoJoYv/DfFDMFS2+JSRpDBoyuEcz3P8UkCV/RRF7lZbAgUBdxIbe5d4ewOVafePZMbBZjstjoSaZZN9dtTxdSyHhPjzroGIOCgk7SnSCISk= 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=XLoR70vw; arc=none smtp.client-ip=209.85.214.173 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="XLoR70vw" Received: by mail-pl1-f173.google.com with SMTP id d9443c01a7336-227914acd20so28667525ad.1 for ; Fri, 11 Apr 2025 11:31:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1744396287; x=1745001087; 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=pM14jnQzLfenTA2VQf8LACWxIBUDZfqO9aE4N45FzZU=; b=XLoR70vw9gCqJsq1VS0a9GUaDZ6m36BsFRd6F3vLxjJtnRoz9y2NU52OzNUBy2qvMq MgznG6Evuub7uOaaymz6MXkhAag5UphK5jd9ft1B6v6uBrtFllE2nWCiUDHgdx1uwkgj nT6esq9WvenGHSQEoXS8WNFcK+2HjuW4/dSpuQs5na/azF7gFd35DYN25wXDranIKrr9 voO0i+VDUkPjPUG3hpXEUHUtFbx3RlWRQxVoQdc8ZjhDv1M+8q6z0XfGFVEbnFAhYhJz 5Y4x7X8DqVpbmKpsWyntfZxwp75cBdDelgKKuBLPmeACdO4oA5Wi/6V5TAGPbFr0hgOv hkhg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744396287; x=1745001087; 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=pM14jnQzLfenTA2VQf8LACWxIBUDZfqO9aE4N45FzZU=; b=oOaUmAAvSVFdSLZTVaVSFz4JfB7mzk7XXlm0cq6gWcEpZl0ZPocpIZVg7easE7DMbX oCz+cHMEwW4g9tPFrcZLq4DSrlRoKNcohRIpErxz2GyDYkyH5bK1S8D16wH/En8EUTCE YlkpzmOQjp67dL6B3V26vHcJT1AcBGw4JfW7TNvYU8E9uHjSofbksWK+x3B7LnkwpzjN KqQ6OoOH2kSIDs8KElRMtR/b1h0EjPwy6Mzn17ybkae4VxOeZqkfrwFST57jcvkVkB1/ 3OpdV6xrxMxZIkEn5TNjT0GVqx4dl/rgzwYINlSL88K5fTQIn+hcFAdI1xCve6zMk/my //3w== X-Forwarded-Encrypted: i=1; AJvYcCXpRs6XXunr8l6eqNSaUlMlqAUKKTOwGobzaownMUPglOMAbQR5HZQ+SLwl+WSyyG0bKFVnXpYGJoUWuYQ=@vger.kernel.org X-Gm-Message-State: AOJu0YwgNEvXoa2SQY/3xf1RCK5oFt9RPl9GgwSJ81anBD+yCWepKCxE 0I4BtrKg1F/BLiYUD9QmynawrGrfra7cACZgny2fFjz73YM/20VEUUea3ewawa4= X-Gm-Gg: ASbGncvwTGVxJkshxhktzGbKrXEZlLJRY6rAjAGNU3KEof/MS2ngRypLmcttd7DbP3f 4oU9MaUkPnAiGDNttRoY+jr9rXLK6Re0c5pv1BgBMH+UY3qluM8VDpkhV7C8CBPKlgGiSqorPp0 gNoxKZObXezH5rXRZubxO0CquQ7fLGnmFSOluw4usfTkeb4pGT4XswZJ6RGX9lc5DO8ZOSFIvQE Ilo9dpwklSPdnEpE8Ikms/B41EqELcMCzg5zQtQDIby0qLn7lpS01n5UVTK/8pg/3UMJWWt0Qa+ /SObI0rhLB8gJ94XnmbuqUglfo2A4RfSk6eDlXTR12AUnhNZRK0= X-Google-Smtp-Source: AGHT+IEtX4hz/mJy7qUcYoRPvFiC5yx3emxSTRwYk+VHRrVmB3bxq8sDXdJpR/l+w40hDNnE/Tp2cg== X-Received: by 2002:a17:902:cec5:b0:215:a2f4:d4ab with SMTP id d9443c01a7336-22bea04195dmr46654325ad.7.1744396287499; Fri, 11 Apr 2025 11:31:27 -0700 (PDT) Received: from VM-16-38-fedora.. ([43.135.149.86]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22ac7c95cdcsm53279515ad.118.2025.04.11.11.31.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Apr 2025 11:31:27 -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 3/3] kernfs: switch global kernfs_pr_cont_lock to per-fs lock Date: Sat, 12 Apr 2025 02:31:09 +0800 Message-ID: <20250411183109.6334-4-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_pr_cont_lock) so every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the lock. This patch switches the global kernfs_pr_cont_lock to per-fs lock, which put the spinlock into kernfs_root. Of course, kernfs_pr_cont_buf also needs to be moved to kernfs_root. Signed-off-by: Jinliang Zheng --- fs/kernfs/dir.c | 46 +++++++++++++++++-------------------- fs/kernfs/kernfs-internal.h | 11 +++++++++ 2 files changed, 32 insertions(+), 25 deletions(-) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index d63a96786c9b..29605d7f0ab0 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -17,16 +17,6 @@ =20 #include "kernfs-internal.h" =20 -/* - * 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() - * will perform wakeups when releasing console_sem. Holding rename_lock - * will introduce deadlock if the scheduler reads the kernfs_name in the - * wakeup path. - */ -static DEFINE_SPINLOCK(kernfs_pr_cont_lock); -static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by pr_cont_lock */ - #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb) =20 static bool __kernfs_active(struct kernfs_node *kn) @@ -244,13 +234,15 @@ EXPORT_SYMBOL_GPL(kernfs_path_from_node); void pr_cont_kernfs_name(struct kernfs_node *kn) { unsigned long flags; + struct kernfs_root *root =3D kernfs_root(kn); =20 - spin_lock_irqsave(&kernfs_pr_cont_lock, flags); + spin_lock_irqsave(&root->kernfs_pr_cont_lock, flags); =20 - kernfs_name(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf)); - pr_cont("%s", kernfs_pr_cont_buf); + kernfs_name(kn, root->kernfs_pr_cont_buf, + sizeof(root->kernfs_pr_cont_buf)); + pr_cont("%s", root->kernfs_pr_cont_buf); =20 - spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags); + spin_unlock_irqrestore(&root->kernfs_pr_cont_lock, flags); } =20 /** @@ -263,11 +255,12 @@ void pr_cont_kernfs_path(struct kernfs_node *kn) { unsigned long flags; int sz; + struct kernfs_root *root =3D kernfs_root(kn); =20 - spin_lock_irqsave(&kernfs_pr_cont_lock, flags); + spin_lock_irqsave(&root->kernfs_pr_cont_lock, flags); =20 - sz =3D kernfs_path_from_node(kn, NULL, kernfs_pr_cont_buf, - sizeof(kernfs_pr_cont_buf)); + sz =3D kernfs_path_from_node(kn, NULL, root->kernfs_pr_cont_buf, + sizeof(root->kernfs_pr_cont_buf)); if (sz < 0) { if (sz =3D=3D -E2BIG) pr_cont("(name too long)"); @@ -276,10 +269,10 @@ void pr_cont_kernfs_path(struct kernfs_node *kn) goto out; } =20 - pr_cont("%s", kernfs_pr_cont_buf); + pr_cont("%s", root->kernfs_pr_cont_buf); =20 out: - spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags); + spin_unlock_irqrestore(&root->kernfs_pr_cont_lock, flags); } =20 /** @@ -888,19 +881,21 @@ static struct kernfs_node *kernfs_walk_ns(struct kern= fs_node *parent, { ssize_t len; char *p, *name; + struct kernfs_root *root =3D kernfs_root(parent); =20 - lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem); + lockdep_assert_held_read(&root->kernfs_rwsem); =20 - spin_lock_irq(&kernfs_pr_cont_lock); + spin_lock_irq(&root->kernfs_pr_cont_lock); =20 - len =3D strscpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf)); + len =3D strscpy(root->kernfs_pr_cont_buf, path, + sizeof(root->kernfs_pr_cont_buf)); =20 if (len < 0) { - spin_unlock_irq(&kernfs_pr_cont_lock); + spin_unlock_irq(&root->kernfs_pr_cont_lock); return NULL; } =20 - p =3D kernfs_pr_cont_buf; + p =3D root->kernfs_pr_cont_buf; =20 while ((name =3D strsep(&p, "/")) && parent) { if (*name =3D=3D '\0') @@ -908,7 +903,7 @@ static struct kernfs_node *kernfs_walk_ns(struct kernfs= _node *parent, parent =3D kernfs_find_ns(parent, name, ns); } =20 - spin_unlock_irq(&kernfs_pr_cont_lock); + spin_unlock_irq(&root->kernfs_pr_cont_lock); =20 return parent; } @@ -995,6 +990,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_sy= scall_ops *scops, init_rwsem(&root->kernfs_supers_rwsem); INIT_LIST_HEAD(&root->supers); rwlock_init(&root->kernfs_rename_lock); + spin_lock_init(&root->kernfs_pr_cont_lock); =20 /* * On 64bit ino setups, id is ino. On 32bit, low 32bits are ino. diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index 6061b6f70d2a..c7fe50955e8c 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -55,6 +55,17 @@ struct kernfs_root { rwlock_t kernfs_rename_lock; =20 struct rcu_head rcu; + + /* + * 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() + * will perform wakeups when releasing console_sem. Holding rename_lock + * will introduce deadlock if the scheduler reads the kernfs_name in the + * wakeup path. + */ + spinlock_t kernfs_pr_cont_lock; + /* protected by pr_cont_lock */ + char kernfs_pr_cont_buf[PATH_MAX]; }; =20 /* +1 to avoid triggering overflow warning when negating it */ --=20 2.48.1