From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) (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 0D1EC17745; Thu, 21 Dec 2023 07:39:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="CyGUP3iE" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=LWqF/Y37SmpDLulc6cjBB+/HUzaRe+A8SRPSmTNrLps=; b=CyGUP3iEahTK1hH0NTvCsSV65A hR5EBSWyJFMDw5Em/W73Lk0ToDAhpzo+r2qf0I0FbbaVJjb4n34g8JivJiLuafLEVZsA7BfnEq1Tt EhZwoLITM8IE3pgeguDCii/5IzVeW8gKUrQT5nS1Qyo9TJp88KzQfBQfhUB3uevoye4+BMKSyKOdh jcnZU1rCS9/d25zXM6mwp7akEeTeLX1antM5/IybK65z+GgT2X0B0OCdx19x5KGqDecYUx2/bboq+ 2qs9K2Iyx5nko5XWQ2xja1HiLXAsh5CSc9u0+2z+3RQk8rF+1sdzAhy/jXEeSAb3jr1qUO2wjRrww 7HOtJ0UQ==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1rGDee-001Ji1-1S; Thu, 21 Dec 2023 07:39:40 +0000 Date: Thu, 21 Dec 2023 07:39:40 +0000 From: Al Viro To: Gabriel Krisman Bertazi Cc: ebiggers@kernel.org, jaegeuk@kernel.org, tytso@mit.edu, linux-f2fs-devel@lists.sourceforge.net, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v2 8/8] fscrypt: Move d_revalidate configuration back into fscrypt Message-ID: <20231221073940.GC1674809@ZenIV> References: <20231215211608.6449-1-krisman@suse.de> <20231215211608.6449-9-krisman@suse.de> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231215211608.6449-9-krisman@suse.de> Sender: Al Viro On Fri, Dec 15, 2023 at 04:16:08PM -0500, Gabriel Krisman Bertazi wrote: > +static const struct dentry_operations fscrypt_dentry_ops = { > + .d_revalidate = fscrypt_d_revalidate, > +}; > + > int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, > struct fscrypt_name *fname) > { > @@ -106,6 +110,10 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, > spin_lock(&dentry->d_lock); > dentry->d_flags |= DCACHE_NOKEY_NAME; > spin_unlock(&dentry->d_lock); > + > + /* Give preference to the filesystem hooks, if any. */ > + if (!dentry->d_op) > + d_set_d_op(dentry, &fscrypt_dentry_ops); > } > return err; Hmm... Could we simply set ->s_d_op to &fscrypt_dentry_ops in non-ci case *AND* have __fscrypt_prepare_lookup() clear DCACHE_OP_REVALIDATE in case when it's not setting DCACHE_NOKEY_NAME and ->d_op->d_revalidate is equal to fscrypt_d_revalidate? I mean, spin_lock(&dentry->d_lock); if (fname->is_nokey_name) dentry->d_flags |= DCACHE_NOKEY_NAME; else if (dentry->d_flags & DCACHE_OP_REVALIDATE && dentry->d_op->d_revalidate == fscrypt_d_revalidate) dentry->d_flags &= ~DCACHE_OP_REVALIDATE; spin_unlock(&dentry->d_lock); here + always set ->s_d_op for ext4 and friends (conditional upon the CONFIG_UNICODE). No encryption - fine, you get ->is_nokey_name false from the very beginning, DCACHE_OP_REVALIDATE is cleared and VFS won't ever call ->d_revalidate(); not even the first time. Yes, you pay minimal price in dentry_unlink_inode() when we hit if (dentry->d_op && dentry->d_op->d_iput) and bugger off after the second fetch instead of the first one. I would be quite surprised if it turns out to be measurable, but if it is, we can always add DCACHE_OP_IPUT to flags. Similar for ->d_op->d_release (called in the end of __dentry_kill()). Again, that only makes sense if we get a measurable overhead from that.