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Date:   Mon, 11 Nov 2019 12:28:12 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
        linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Chandan Rajendra <chandan@...ux.ibm.com>
Subject: Re: [PATCH v2 0/2] ext4: support encryption with blocksize !=
 PAGE_SIZE

On Wed, Nov 06, 2019 at 01:54:40PM -0800, Eric Biggers wrote:
> On Tue, Oct 22, 2019 at 08:33:10PM -0700, Eric Biggers wrote:
> > Hello,
> > 
> > This patchset makes ext4 support encryption on filesystems where the
> > filesystem block size is not equal to PAGE_SIZE.  This allows e.g.
> > PowerPC systems to use ext4 encryption.
> > 
> > Most of the work for this was already done in prior kernel releases; now
> > the only part missing is decryption support in block_read_full_page().
> > Chandan Rajendra has proposed a patchset "Consolidate FS read I/O
> > callbacks code" [1] to address this and do various other things like
> > make ext4 use mpage_readpages() again, and make ext4 and f2fs share more
> > code.  But it doesn't seem to be going anywhere.
> > 
> > Therefore, I propose we simply add decryption support to
> > block_read_full_page() for now.  This is a fairly small change, and it
> > gets ext4 encryption with subpage-sized blocks working.
> > 
> > Note: to keep things simple I'm just allocating the work object from the
> > bi_end_io function with GFP_ATOMIC.  But if people think it's necessary,
> > it could be changed to use preallocation like the page-based read path.
> > 
> > Tested with 'gce-xfstests -c ext4/encrypt_1k -g auto', using the new
> > "encrypt_1k" config I created.  All tests pass except for those that
> > already fail or are excluded with the encrypt or 1k configs, and 2 tests
> > that try to create 1023-byte symlinks which fails since encrypted
> > symlinks are limited to blocksize-3 bytes.  Also ran the dedicated
> > encryption tests using 'kvm-xfstests -c ext4/1k -g encrypt'; all pass,
> > including the on-disk ciphertext verification tests.
> > 
> > [1] https://lkml.kernel.org/linux-fsdevel/20190910155115.28550-1-chandan@linux.ibm.com/T/#u
> > 
> > Changed v1 => v2:
> >   - Added check for S_ISREG() which technically should be there, though
> >     it happens not to matter currently.
> > 
> > Chandan Rajendra (1):
> >   ext4: Enable encryption for subpage-sized blocks
> > 
> > Eric Biggers (1):
> >   fs/buffer.c: support fscrypt in block_read_full_page()
> > 
> >  Documentation/filesystems/fscrypt.rst |  4 +--
> >  fs/buffer.c                           | 48 ++++++++++++++++++++++++---
> >  fs/ext4/super.c                       |  7 ----
> >  3 files changed, 45 insertions(+), 14 deletions(-)
> > 
> 
> Any more comments on this?
> 
> Ted, are you interested in taking this through the ext4 tree for 5.5?
> 

Ping.

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