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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 198E4C433EF for ; Tue, 16 Nov 2021 19:43:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E3A8761B5E for ; Tue, 16 Nov 2021 19:43:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240126AbhKPTqV (ORCPT ); Tue, 16 Nov 2021 14:46:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56188 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239957AbhKPTqS (ORCPT ); Tue, 16 Nov 2021 14:46:18 -0500 Received: from mail-pg1-x529.google.com (mail-pg1-x529.google.com [IPv6:2607:f8b0:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 97909C061570 for ; Tue, 16 Nov 2021 11:43:21 -0800 (PST) Received: by mail-pg1-x529.google.com with SMTP id q12so97727pgh.5 for ; Tue, 16 Nov 2021 11:43:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=aPOYW20bP9axR+huv2l40pnrQ8xrHrsRaFVlcPUQJRE=; b=b/tDytIcwvHt9kT147ZgbyOV6huXsUHxKjT6i253GBWKL2vi5zQ7KH1+WrlJEOfQAT VaCxa5zdckSJWk+FiaUpAFA9sbQwvusr1KpE1wM3I6qgqW8ggHpbkCN+pMu1x7Gf9AI0 bFjES3U9eJD40dh0IYXqJ3EoGYWuuWrmi+w03HB05kQ92f5Y/Qlm3cfAhZFpBYZCxB+h lvLmCauoIW+YgCuj5/CyphT/6baQ2ZnsAGkfdbMy8pVQc1HA80xbtobRT5i4+0eEx1Gl WzTkOAeZUg8c3Cas8R6Gj7xfsoV1d6N7LMCEE4oX1q645kNtAlAYlJWIGsE2kO9JNYyp lk3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :mime-version:content-transfer-encoding; bh=aPOYW20bP9axR+huv2l40pnrQ8xrHrsRaFVlcPUQJRE=; b=T/4CALUJjSjFXWxLrlVanNMThWOer8DJIuSWP5lzXZ8IAcCPxtc0RTIbU6z35uR2UB DQlltczKNhQSTuzPwkLjwcCz6G2grFlV83KKMTPFc5JeYrmjtU6ud/p8iybZot+/q/YY dfPLr+syari6iOERbokQuaODAsRoyu9VOkqO0S9PcxwjYnRZI0c+Pk7yUy/QZtOFkK3K DGsrPf+FDieTn/iF1S49gs4qN6R6sgr7MJXsWyad8afwyOn/Oy9EFYIwct0ETx6Wm1TS /4J3ovt6tAdLo7IF/VbSzCr+wBD1Yxz0jEjV0jpHOPErZFgMr69eOHmulSRbwwcz5C90 6V1g== X-Gm-Message-State: AOAM532Xo9KWYo1uXrpHawKbezEwIDITAlb/jZzz/QRlzExK/BWbRTHc ZK+KcwGPZNzlYK8aqm5rhXdljGdhR8k= X-Google-Smtp-Source: ABdhPJw/3XDiznj8S8mykd65Ahpj91WYQGjhIr10eS9bIqY6W/XSiOsBfVnjNQtdVdPz0NI9v8UWoA== X-Received: by 2002:aa7:88cb:0:b0:49f:ad17:c08 with SMTP id k11-20020aa788cb000000b0049fad170c08mr42243482pff.19.1637091801086; Tue, 16 Nov 2021 11:43:21 -0800 (PST) Received: from bbox-1.mtv.corp.google.com ([2620:15c:211:201:3a93:19e8:b5b5:97fd]) by smtp.gmail.com with ESMTPSA id ep15sm2407300pjb.3.2021.11.16.11.43.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Nov 2021 11:43:20 -0800 (PST) Sender: Minchan Kim From: Minchan Kim To: Greg Kroah-Hartman , Tejun Heo Cc: LKML , Minchan Kim Subject: [RFC PATCH] kernfs: release kernfs_mutex before the inode allocation Date: Tue, 16 Nov 2021 11:43:17 -0800 Message-Id: <20211116194317.1430399-1-minchan@kernel.org> X-Mailer: git-send-email 2.34.0.rc1.387.gb447b232ab-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The kernfs implementation has big lock granularity(kernfs_rwsem) so every kernfs-based(e.g., sysfs, cgroup, dmabuf) fs are able to compete the lock. Thus, if one of userspace goes the sleep under holding the lock for a long time, rest of them should wait it. A example is the holder goes direct reclaim with the lock since it needs memory allocation. Let's fix it at common technique that release the lock and then allocate the memory. Fortunately, kernfs looks like have an refcount so I hope it's fine. Signed-off-by: Minchan Kim --- fs/kernfs/dir.c | 14 +++++++++++--- fs/kernfs/inode.c | 2 +- fs/kernfs/kernfs-internal.h | 1 + 3 files changed, 13 insertions(+), 4 deletions(-) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 8e0a1378a4b1..ecdb2975060d 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -1119,9 +1119,17 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir, up_read(&kernfs_rwsem); return NULL; } - inode = kernfs_get_inode(dir->i_sb, kn); - if (!inode) - inode = ERR_PTR(-ENOMEM); + kernfs_get(kn); + up_read(&kernfs_rwsem); + inode = iget_locked(dir->i_sb, kernfs_ino(kn)); + if (!inode) { + kernfs_put(kn); + return ERR_PTR(-ENOMEM); + } + down_read(&kernfs_rwsem); + if (inode->i_state & I_NEW) + kernfs_init_inode(kn, inode); + kernfs_put(kn); } /* * Needed for negative dentry validation. diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index c0eae1725435..6e2004010435 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -195,7 +195,7 @@ int kernfs_iop_getattr(struct user_namespace *mnt_userns, return 0; } -static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) +void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) { kernfs_get(kn); inode->i_private = kn; diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index f9cc912c31e1..eef7656f7cd8 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -118,6 +118,7 @@ int kernfs_iop_getattr(struct user_namespace *mnt_userns, u32 request_mask, unsigned int query_flags); ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size); int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr); +void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode); /* * dir.c -- 2.34.0.rc1.387.gb447b232ab-goog