From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Subject: Re: [PATCH] fscrypt: cache decrypted symlink target in ->i_link Date: Tue, 9 Apr 2019 17:45:54 -0700 Message-ID: <20190410004553.GA2454@sol.localdomain> References: <20190409233544.156665-1-ebiggers@kernel.org> <20190410003346.GT2217@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1hE1No-0001OD-Mg for linux-f2fs-devel@lists.sourceforge.net; Wed, 10 Apr 2019 00:46:32 +0000 Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-4.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) id 1hE1Nl-00CL9y-5G for linux-f2fs-devel@lists.sourceforge.net; Wed, 10 Apr 2019 00:46:32 +0000 Content-Disposition: inline In-Reply-To: <20190410003346.GT2217@ZenIV.linux.org.uk> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Al Viro Cc: linux-fsdevel@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net On Wed, Apr 10, 2019 at 01:33:46AM +0100, Al Viro wrote: > On Tue, Apr 09, 2019 at 04:35:44PM -0700, Eric Biggers wrote: > > From: Eric Biggers > > > > Path lookups that traverse encrypted symlink(s) are very slow because > > each encrypted symlink needs to be decrypted each time it's followed. > > > > Make encrypted symlinks faster by caching the decrypted symlink target > > in ->i_link. The first call to ->get_link() sets it; later calls simply > > return it. ->symlink() also sets it when the symlink is created. > > > > When the inode's ->i_crypt_info is freed, ->i_link is freed too. > > > > Note: RCU-delayed freeing of ->i_link is not yet implemented. > > Therefore, for now even when ->i_link is set, path lookups must continue > > to drop out of RCU-walk mode when following an encrypted symlink. > > And how the devil would they continue to do that, if I might ask? > ->get_link() is *NOT* called if ->i_link is non-NULL, period. You're right, I didn't notice that ->get_link() isn't called when ->i_link is non-NULL. But that being the case, what's the point of simple_get_link()? - Eric