From patchwork Wed Nov 1 06:20:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 13442542 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A1E65224 for ; Wed, 1 Nov 2023 06:21:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="KwiIsE6J" 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 047D910A for ; Tue, 31 Oct 2023 23:21:06 -0700 (PDT) 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=V//OsntlN/Gep20c5b55GzSyavMNgG4NgGG0fgQjpcU=; b=KwiIsE6Jce/0SVmi7gjQIn1rE5 Dgi4yrEBZTxJE8Hwm4S4ui0ST0VMU3KMP7QMcykvsBh0PvkA1CThdiedShpM/z5WBvYR1QEckS0XJ h9k7lajhluf5m8AXHSZkVrUjXtE26dUi0auzX9DeqkxRH5R7EKtdISUq0VVUY2/MZw2gzp21vyA8D 0AYUngX0ce5ttwCfinOCAVC/9ciFQ3a6ken2bytQNTtKCnxPPi9uPbw/JVoXPqrMbgXDcmTr062iY aopjNWM9l0H/3GH9PXojhNVUOgiIm5RkAsei0F37uDEsJCtPASVAKcR/ry92saB42PzlqELrMyz4v KUXyb7RA==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1qy4bB-008pbN-1Q; Wed, 01 Nov 2023 06:21:05 +0000 From: Al Viro To: Linus Torvalds Cc: linux-fsdevel@vger.kernel.org Subject: [PATCH 07/15] dentry_kill(): don't bother with retain_dentry() on slow path Date: Wed, 1 Nov 2023 06:20:56 +0000 Message-Id: <20231101062104.2104951-7-viro@zeniv.linux.org.uk> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231101062104.2104951-1-viro@zeniv.linux.org.uk> References: <20231031061226.GC1957730@ZenIV> <20231101062104.2104951-1-viro@zeniv.linux.org.uk> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: Al Viro 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 c89337ae30ce..7931f5108581 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)