linux-ext4 - Re: [PATCH V3 6/7] Add decryption support for sub-pagesized blocks

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Date:   Fri, 21 Jun 2019 14:29:17 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Chandan Rajendra <chandan@...ux.ibm.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fscrypt@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jaegeuk@...nel.org, yuchao0@...wei.com,
        hch@...radead.org
Subject: Re: [PATCH V3 6/7] Add decryption support for sub-pagesized blocks

On Sun, Jun 16, 2019 at 09:38:12PM +0530, Chandan Rajendra wrote:
> To support decryption of sub-pagesized blocks this commit adds code to,
> 1. Track buffer head in "struct read_callbacks_ctx".
> 2. Pass buffer head argument to all read callbacks.
> 3. Add new fscrypt helper to decrypt the file data referred to by a
>    buffer head.
> 
> Signed-off-by: Chandan Rajendra <chandan@...ux.ibm.com>
> ---
>  fs/buffer.c                    |  55 +++++++++------
>  fs/crypto/bio.c                |  21 +++++-
>  fs/f2fs/data.c                 |   2 +-
>  fs/mpage.c                     |   2 +-
>  fs/read_callbacks.c            | 118 +++++++++++++++++++++++++--------
>  include/linux/buffer_head.h    |   1 +
>  include/linux/read_callbacks.h |  13 +++-
>  7 files changed, 158 insertions(+), 54 deletions(-)
> 

This is another patch that unnecessarily changes way too many components at
once.  My suggestions elsewhere would resolve this, though:

- This patch changes fs/f2fs/data.c and fs/mpage.c only to pass a NULL
  buffer_head to read_callbacks_setup().  But as per my comments on patch 1,
  read_callbacks_setup() should be split into read_callbacks_setup_bio() and
  read_callbacks_end_bh().

- This patch changes fs/crypto/ only to add support for the buffer_head
  decryption work.  But as per my comments on patch 1, that should be in
  read_callbacks.c instead.

And adding buffer_head support to fs/read_callbacks.c should be its own patch,
*or* should simply be folded into the patch that adds fs/read_callbacks.c.

Then the only thing remaining in this patch would be updating fs/buffer.c to
make it use the read_callbacks, which should be retitled to something like
"fs/buffer.c: add decryption support via read_callbacks".

- Eric