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[209.132.180.67]) by mx.google.com with ESMTP id z6si44467769pln.54.2019.05.02.11.17.02; Thu, 02 May 2019 11:17:24 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-ext4-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=hqeYSoO4; spf=pass (google.com: best guess record for domain of linux-ext4-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-ext4-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726126AbfEBSQT (ORCPT + 99 others); Thu, 2 May 2019 14:16:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:50840 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726120AbfEBSQT (ORCPT ); Thu, 2 May 2019 14:16:19 -0400 Received: from gmail.com (unknown [104.132.1.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5C9E5205F4; Thu, 2 May 2019 18:16:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556820977; bh=aENbewv6gIVI63hHJV1DryX63oKvmh/WF/btWzUFUMk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hqeYSoO4ZRe1722GO9trLTxlRKWYuYUhpRM25njMTVJRJatv0qy/100ozsMjm7WTq 7eeD+Y9THKqO4gs3Kj6xVQnkX+saVGU7CpRr+KhmtjGPJeD8lE35pGoVZ/b66OUBeL mZDAgWmI2m8A6sbGEA5NQ+J2o0yLrQDTBlIEiQDQ= Date: Thu, 2 May 2019 11:16:15 -0700 From: Eric Biggers To: Chandan Rajendra Cc: tytso@mit.edu, linux-f2fs-devel@lists.sourceforge.net, hch@infradead.org, linux-fscrypt@vger.kernel.org, adilger.kernel@dilger.ca, linux-fsdevel@vger.kernel.org, jaegeuk@kernel.org, linux-ext4@vger.kernel.org Subject: Re: [f2fs-dev] [PATCH V2 10/13] fscrypt_encrypt_page: Loop across all blocks mapped by a page range Message-ID: <20190502181614.GA35523@gmail.com> References: <20190428043121.30925-1-chandan@linux.ibm.com> <4666731.7CFakFE75r@localhost.localdomain> <20190501222859.GA127264@gmail.com> <11064745.d7X6JK8F7Z@dhcp-9-193-88-253> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <11064745.d7X6JK8F7Z@dhcp-9-193-88-253> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Hi Chandan, On Thu, May 02, 2019 at 11:22:05AM +0530, Chandan Rajendra wrote: > On Thursday, May 2, 2019 3:59:01 AM IST Eric Biggers wrote: > > Hi Chandan, > > > > On Wed, May 01, 2019 at 08:19:35PM +0530, Chandan Rajendra wrote: > > > On Wednesday, May 1, 2019 4:38:41 AM IST Eric Biggers wrote: > > > > On Tue, Apr 30, 2019 at 10:11:35AM -0700, Eric Biggers wrote: > > > > > On Sun, Apr 28, 2019 at 10:01:18AM +0530, Chandan Rajendra wrote: > > > > > > For subpage-sized blocks, this commit now encrypts all blocks mapped by > > > > > > a page range. > > > > > > > > > > > > Signed-off-by: Chandan Rajendra > > > > > > --- > > > > > > fs/crypto/crypto.c | 37 +++++++++++++++++++++++++------------ > > > > > > 1 file changed, 25 insertions(+), 12 deletions(-) > > > > > > > > > > > > diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c > > > > > > index 4f0d832cae71..2d65b431563f 100644 > > > > > > --- a/fs/crypto/crypto.c > > > > > > +++ b/fs/crypto/crypto.c > > > > > > @@ -242,18 +242,26 @@ struct page *fscrypt_encrypt_page(const struct inode *inode, > > > > > > > > > > Need to update the function comment to clearly explain what this function > > > > > actually does now. > > > > > > > > > > > { > > > > > > struct fscrypt_ctx *ctx; > > > > > > struct page *ciphertext_page = page; > > > > > > + int i, page_nr_blks; > > > > > > int err; > > > > > > > > > > > > BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0); > > > > > > > > > > > > > > > > Make a 'blocksize' variable so you don't have to keep calling i_blocksize(). > > > > > > > > > > Also, you need to check whether 'len' and 'offs' are filesystem-block-aligned, > > > > > since the code now assumes it. > > > > > > > > > > const unsigned int blocksize = i_blocksize(inode); > > > > > > > > > > if (!IS_ALIGNED(len | offs, blocksize)) > > > > > return -EINVAL; > > > > > > > > > > However, did you check whether that's always true for ubifs? It looks like it > > > > > may expect to encrypt a prefix of a block, that is only padded to the next > > > > > 16-byte boundary. > > > > > > > > > > > + page_nr_blks = len >> inode->i_blkbits; > > > > > > + > > > > > > if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) { > > > > > > /* with inplace-encryption we just encrypt the page */ > > > > > > - err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page, > > > > > > - ciphertext_page, len, offs, > > > > > > - gfp_flags); > > > > > > - if (err) > > > > > > - return ERR_PTR(err); > > > > > > - > > > > > > + for (i = 0; i < page_nr_blks; i++) { > > > > > > + err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, > > > > > > + lblk_num, page, > > > > > > + ciphertext_page, > > > > > > + i_blocksize(inode), offs, > > > > > > + gfp_flags); > > > > > > + if (err) > > > > > > + return ERR_PTR(err); > > > > > > > > Apparently ubifs does encrypt data shorter than the filesystem block size, so > > > > this part is wrong. > > > > > > > > I suggest we split this into two functions, fscrypt_encrypt_block_inplace() and > > > > fscrypt_encrypt_blocks(), so that it's conceptually simpler what each function > > > > does. Currently this works completely differently depending on whether the > > > > filesystem set FS_CFLG_OWN_PAGES in its fscrypt_operations, which is weird. > > > > > > > > I also noticed that using fscrypt_ctx for writes seems to be unnecessary. > > > > AFAICS, page_private(bounce_page) could point directly to the pagecache page. > > > > That would simplify things a lot, especially since then fscrypt_ctx could be > > > > removed entirely after you convert reads to use read_callbacks_ctx. > > > > > > > > IMO, these would be worthwhile cleanups for fscrypt by themselves, without > > > > waiting for the read_callbacks stuff to be finalized. Finalizing the > > > > read_callbacks stuff will probably require reaching a consensus about how they > > > > should work with future filesystem features like fsverity and compression. > > > > > > > > So to move things forward, I'm considering sending out a series with the above > > > > cleanups for fscrypt, plus the equivalent of your patches: > > > > > > > > "fscrypt_encrypt_page: Loop across all blocks mapped by a page range" > > > > "fscrypt_zeroout_range: Encrypt all zeroed out blocks of a page" > > > > "Add decryption support for sub-pagesized blocks" (fs/crypto/ part only) > > > > > > > > Then hopefully we can get all that applied for 5.3 so that fs/crypto/ itself is > > > > ready for blocksize != PAGE_SIZE; and get your changes to ext4_bio_write_page(), > > > > __ext4_block_zero_page_range(), and ext4_block_write_begin() applied too, so > > > > that ext4 is partially ready for encryption with blocksize != PAGE_SIZE. > > > > > > > > Then only the read_callbacks stuff will remain, to get encryption support into > > > > fs/mpage.c and fs/buffer.c. Do you think that's a good plan? > > > > > > Hi Eric, > > > > > > IMHO, I will continue posting the next version of the current patchset and if > > > there are no serious reservations from FS maintainers the "read callbacks" > > > patchset can be merged. In such a scenario, the cleanups being > > > non-complicated, can be merged later. > > > > > > > Most of the patches I have in mind are actually things that are in your patchset > > already, or have been requested, or will be requested eventually :-). I'm > > concerned that people will keep going back and forth on this patchset for a lot > > longer, arguing about fsverity, compression, details of the fs/crypto/ stuff, > > etc. Moreover it's based on unmerged patches that add the fsverity feature, so > > it can't be merged as-is anyway. > > > > IMO, it's also difficult for people to review the read_callbacks stuff when it's > > mixed in with lots of other fscrypt and ext4 changes for blocksize != PAGE_SIZE. > > > > I actually have a patchset almost ready already, so I'm going to send it out and > > see what you think. It *should* make things a lot easier for you, since then > > you can base a much smaller read_callbacks patchset on top of it. > > One of the things that I am concerned most about is the fact that the more we > delay merging read_callbacks patchset, the more the chances of filesystems > adding further operations that get executed after read I/O completes. Most of > the time, these implementations tend to have filesystem specific changes which > are going to be very difficult (impossible?) to make them work with > read_callback patchset. So instead of making things easier, delaying merging > the read_callback patchset ends up actually having the opposite effect. > > With the read_callback patchset merged, FS feature developers will take > read_callback framework into consideration before designing/implementing new > related features. > The main problems are that your patchset mixes up conceptually unrelated changes, and is dependent on future filesystem features. See how it starts by adding read_callbacks support for both fscrypt *and* fsverity (the latter of which is not merged yet), then updates fs/crypto/ to support subpage blocks, *then* goes back and finishes read_callbacks to support buffer_heads since that depended on the fs/crypto/ changes. The ext4 changes for subpage blocks are mixed in too throughout the patchset. So I don't think it can proceed in its current form; it's too much for anyone to handle at once. And I see your first patchset for ext4 encryption with subpage blocks was sent almost a year and a half ago, so it's indeed been going in circles for a while. But based on your work I've been able to get the fs/crypto/ and ext4 preparations for subpage blocks into a clean set of changes by themselves. There are needed in any case, so IMO we should take them first in order to unblock the rest. I don't really understand your point about forcing filesystems to be compatible with read_callbacks. The whole point of read_callbacks is that it's a common support layer which makes it easier for filesystems to do the things they're doing anyway, or will be doing. So it shouldn't affect filesystem designs. Thanks! - Eric