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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5C3BC61D97 for ; Fri, 24 Nov 2023 06:05:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344609AbjKXGFW (ORCPT ); Fri, 24 Nov 2023 01:05:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229453AbjKXGEU (ORCPT ); Fri, 24 Nov 2023 01:04:20 -0500 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [IPv6:2a03:a000:7:0:5054:ff:fe1c:15ff]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E143C10D0; Thu, 23 Nov 2023 22:04:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=vqFH5rERW58IIdMxyKTO+oPeZnb8OZczTTpmKipGyrA=; b=IZalQm1CDM/26zqZNWLkuzZQnL XoCFW8H56OWRSgycnTzbTmahD10SLdxGszLx2xyNWABvWa2x0BFbuIcT0xuC3LKURvZmBqaH7VDp1 viy2p+jmxKAOv1za7I1rZM4eHxwbJIa6urXvjPrb+grgYsE2NGb2ojtftJhvNm8eRguMUIDzQ8xv3 nwfibLMUZxvrvT6JjL2BZmtzIcYmRjyGgdZbBXT5LPjgZ6LZBN+pTOD0Suj2GSYW/4VfZEzeF15Q2 V1T8UOCAuCh26oo7Cv8hUS0rw3HeVbREBIcFly1u+l+Gk+FTqeLAdfwrK4yy5V6lrNLN8z49Ll1Fy ohFGTtwg==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1r6PIe-002PuZ-11; Fri, 24 Nov 2023 06:04:24 +0000 From: Al Viro To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Christian Brauner , linux-kernel@vger.kernel.org Subject: [PATCH v3 12/21] dentry_kill(): don't bother with retain_dentry() on slow path Date: Fri, 24 Nov 2023 06:04:13 +0000 Message-Id: <20231124060422.576198-12-viro@zeniv.linux.org.uk> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231124060422.576198-1-viro@zeniv.linux.org.uk> References: <20231124060200.GR38156@ZenIV> <20231124060422.576198-1-viro@zeniv.linux.org.uk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We have already checked it and dentry used to look not worthy of keeping. The only hard obstacle to evicting dentry is non-zero refcount; everything else is advisory - e.g. memory pressure could evict any dentry found with refcount zero. On the slow path in dentry_kill() we had dropped and regained ->d_lock; we must recheck the refcount, but everything else is not worth bothering with. Note that filesystem can not count upon ->d_delete() being called for dentry - not even once. Again, memory pressure (as well as d_prune_aliases(), or attempted rmdir() of ancestor, or...) will not call ->d_delete() at all. So from the correctness point of view we are fine doing the check only once. And it makes things simpler down the road. Signed-off-by: Al Viro --- fs/dcache.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index b527db8e5901..80992e49561c 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -739,14 +739,10 @@ static struct dentry *dentry_kill(struct dentry *dentry) spin_lock(&dentry->d_lock); parent = lock_parent(dentry); got_locks: - if (unlikely(dentry->d_lockref.count != 1)) { - dentry->d_lockref.count--; - } else if (likely(!retain_dentry(dentry))) { - dentry->d_lockref.count--; + dentry->d_lockref.count--; + if (likely(dentry->d_lockref.count == 0)) { __dentry_kill(dentry); return parent; - } else { - dentry->d_lockref.count--; } /* we are keeping it, after all */ if (inode) -- 2.39.2