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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15C2DC47254 for ; Fri, 8 May 2020 12:23:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB126208D6 for ; Fri, 8 May 2020 12:23:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="OOLeXBCf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727801AbgEHMXg (ORCPT ); Fri, 8 May 2020 08:23:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1727769AbgEHMXb (ORCPT ); Fri, 8 May 2020 08:23:31 -0400 Received: from forwardcorp1o.mail.yandex.net (forwardcorp1o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::193]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0808BC05BD43 for ; Fri, 8 May 2020 05:23:31 -0700 (PDT) Received: from mxbackcorp2j.mail.yandex.net (mxbackcorp2j.mail.yandex.net [IPv6:2a02:6b8:0:1619::119]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id 389F62E1574; Fri, 8 May 2020 15:23:29 +0300 (MSK) Received: from myt4-18a966dbd9be.qloud-c.yandex.net (myt4-18a966dbd9be.qloud-c.yandex.net [2a02:6b8:c00:12ad:0:640:18a9:66db]) by mxbackcorp2j.mail.yandex.net (mxbackcorp/Yandex) with ESMTP id ar427vyawi-NSX4ptWY; Fri, 08 May 2020 15:23:29 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1588940609; bh=liJknFRYDA0nUUv0ro+iQXHRLau6qws9t8QCP/DSyVg=; h=In-Reply-To:Message-ID:References:Date:To:From:Subject:Cc; b=OOLeXBCfwoE6ZufUWCYkDj83HXktllePJsnMsIx9vr5wx0QX2UAsr1HG8rSOu8Omg hCskXJGWC8zlMJECTFy+TE+rgXbOXgjyzOM2bJUMmsZLj+koG8MwVHwzsFZVqOPa1c kb/l7qjGID09yskyKryJGtYdxXnUU4e2bJEkShxc= Authentication-Results: mxbackcorp2j.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-vpn.dhcp.yndx.net (dynamic-vpn.dhcp.yndx.net [2a02:6b8:b080:7008::1:4]) by myt4-18a966dbd9be.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id uFJknMXhLs-NSWiskNQ; Fri, 08 May 2020 15:23:28 +0300 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client certificate not present) Subject: [PATCH RFC 6/8] dcache: stop walking siblings if remaining dentries all negative From: Konstantin Khlebnikov To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro Cc: Waiman Long Date: Fri, 08 May 2020 15:23:28 +0300 Message-ID: <158894060799.200862.477468763047350875.stgit@buzz> In-Reply-To: <158893941613.200862.4094521350329937435.stgit@buzz> References: <158893941613.200862.4094521350329937435.stgit@buzz> User-Agent: StGit/0.22-32-g6a05 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Most walkers are interested only in positive dentries. Changes in simple_* libfs helpers are mostly cosmetic: it shouldn't cache negative dentries unless uses d_delete other than always_delete_dentry(). Signed-off-by: Konstantin Khlebnikov --- fs/dcache.c | 10 ++++++++++ fs/libfs.c | 10 +++++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/fs/dcache.c b/fs/dcache.c index 44c6832d21d6..0fd2e02e507b 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1442,6 +1442,9 @@ static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry) struct check_mount *info = data; struct path path = { .mnt = info->mnt, .dentry = dentry }; + if (d_is_tail_negative(dentry)) + return D_WALK_SKIP_SIBLINGS; + if (likely(!d_mountpoint(dentry))) return D_WALK_CONTINUE; if (__path_is_mountpoint(&path)) { @@ -1688,6 +1691,10 @@ void shrink_dcache_for_umount(struct super_block *sb) static enum d_walk_ret find_submount(void *_data, struct dentry *dentry) { struct dentry **victim = _data; + + if (d_is_tail_negative(dentry)) + return D_WALK_SKIP_SIBLINGS; + if (d_mountpoint(dentry)) { __dget_dlock(dentry); *victim = dentry; @@ -3159,6 +3166,9 @@ static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry) { struct dentry *root = data; if (dentry != root) { + if (d_is_tail_negative(dentry)) + return D_WALK_SKIP_SIBLINGS; + if (d_unhashed(dentry) || !dentry->d_inode) return D_WALK_SKIP; diff --git a/fs/libfs.c b/fs/libfs.c index 3759fbacf522..de944c241cf0 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -106,6 +106,10 @@ static struct dentry *scan_positives(struct dentry *cursor, spin_lock(&dentry->d_lock); while ((p = p->next) != &dentry->d_subdirs) { struct dentry *d = list_entry(p, struct dentry, d_child); + + if (d_is_tail_negative(d)) + break; + // we must at least skip cursors, to avoid livelocks if (d->d_flags & DCACHE_DENTRY_CURSOR) continue; @@ -255,7 +259,8 @@ static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev spin_unlock(&d->d_lock); if (likely(child)) break; - } + } else if (d_is_tail_negative(d)) + break; } spin_unlock(&parent->d_lock); dput(prev); @@ -408,6 +413,9 @@ int simple_empty(struct dentry *dentry) spin_lock(&dentry->d_lock); list_for_each_entry(child, &dentry->d_subdirs, d_child) { + if (d_is_tail_negative(child)) + break; + spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); if (simple_positive(child)) { spin_unlock(&child->d_lock);