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From: Chandan Rajendra <chandan@linux.ibm.com>
To: tytso@mit.edu, viro@zeniv.linux.org.uk
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-fscrypt@vger.kernel.org, adilger.kernel@dilger.ca,
	ebiggers@kernel.org, hch@infradead.org, chandanrlinux@gmail.com
Subject: Re: [PATCH V5 0/7] Consolidate FS read I/O callbacks code
Date: Mon, 02 Sep 2019 10:08:13 +0530	[thread overview]
Message-ID: <10742618.thX4IPaW4o@localhost.localdomain> (raw)
In-Reply-To: <20190823132542.13434-1-chandan@linux.ibm.com>

On Friday, August 23, 2019 6:55 PM Chandan Rajendra wrote: 
> This patchset moves the "FS read I/O callbacks" code into a file of its
> own (i.e. fs/read_callbacks.c) and modifies the generic
> do_mpage_readpge() to make use of the functionality provided.
> 
> "FS read I/O callbacks" code implements the state machine that needs
> to be executed after reading data from files that are encrypted and/or
> have verity metadata associated with them.
> 
> With these changes in place, the patchset changes Ext4 to use
> mpage_readpage[s] instead of its own custom ext4_readpage[s]()
> functions. This is done to reduce duplication of code across
> filesystems. Also, "FS read I/O callbacks" source files will be built
> only if CONFIG_FS_ENCRYPTION is enabled.
> 
> The patchset also modifies fs/buffer.c to get file
> encryption/decryption to work with subpage-sized blocks.
> 
> The patches can also be obtained from
> https://github.com/chandanr/linux.git at branch subpage-encryption-v5.

Ted and Al,

Do you have any comments on the patchset?

> 
> Changelog:
> V4 -> V5:
>    1. Since F2FS uses its own workqueue and also since its
>       decompression logic isn't an fs independent entity like fscrypt or
>       fsverity, this patchset drops support for F2FS.
>       The patchset still helps in removing a copy of
>       do_mpage_readpage() from Ext4 (i.e. ext4_readpage()) and also
>       prevents a copy of block_read_full_page() from being added into
>       Ext4 by adding support to "read callbacks" API invocations into
>       block_read_full_page().
> 
> V3 -> V4:
>    1. A new buffer_head flag (i.e. BH_Read_Cb) is introduced to reliably
>       check if a buffer head's content has to be decrypted.
>    2. Fix layering violation. Now the code flow for decryption happens as shown below,
>       FS => read callbacks => fscrypt
>    3. Select FS_READ_CALLBACKS from FS specific kconfig file if FS_ENCRYPTION
>       is enabled.
>    4. Make 'struct read_callbacks_ctx' an opaque structure.
>    5. Make use of FS' endio function rather than implementing one in read
>       callbacks.
>    6. Make read_callbacks.h self-contained.
>    7. Split patchset to separate out ext4 and f2fs changes.
>    
> V2 -> V3:
> 1. Split the V2 patch "Consolidate 'read callbacks' into a new file" into
>    three patches,
>    - Introduce the read_callbacks functionality.
>    - Convert encryption to use read_callbacks.
>    - Remove union from struct fscrypt_context.
> 2. fs/Kconfig
>    Do not explicitly set the default value of 'n' for FS_READ_CALLBACKS.
> 3. fs/crypto/Kconfig
>    Select CONFIG_FS_READ_CALLBACKS only if CONFIG_BLOCK is selected.
> 4. Remove verity associated code in read_callbacks code.
> 5. Introduce a callback argument to read_callbacks_setup() function
>    which gets invoked for each page for bio. F2FS uses this to perform
>    custom operations like decrementing the value of f2fs_sb_info->nr_pages[].
> 6. Encapsulate the details of "read callbacks" (e.g. Usage of "struct
>    read_callbacks *ctx") within its own functions. When CONFIG_FS_READ_CALLBACKS
>    is set to 'n', the corresponding stub functions return approriate error
>    values.
> 7. Split fscrypt_decrypt() function into fscrypt_decrypt_bio() and
>    fscrypt_decrypt_bh().
> 8. Split end_read_callbacks() function into end_read_callbacks_bio() and
>    end_read_callbacks_bh().
> 
> V1 -> V2:
> 1. Removed the phrase "post_read_process" from file names and
>    functions. Instead we now use the phrase "read_callbacks" in its
>    place.
> 2. When performing changes associated with (1), the changes made by
>    the patch "Remove the term 'bio' from post read processing" are
>    made in the earlier patch "Consolidate 'read callbacks' into a new
>    file". Hence the patch "Remove the term 'bio' from post read
>    processing" is removed from the patchset.
> 
> RFC V2 -> V1:
> 1. Test and verify FS_CFLG_OWN_PAGES subset of fscrypt_encrypt_page()
>    code by executing fstests on UBIFS.
> 2. Implement F2fs function call back to check if the contents of a
>    page holding a verity file's data needs to be verified.
> 
> RFC V1 -> RFC V2:
> 1. Describe the purpose of "Post processing code" in the cover letter.
> 2. Fix build errors when CONFIG_FS_VERITY is enabled.
> 
> Chandan Rajendra (7):
>   buffer_head: Introduce BH_Read_Cb flag
>   FS: Introduce read callbacks
>   fs/mpage.c: Integrate read callbacks
>   fs/buffer.c: add decryption support via read_callbacks
>   ext4: Wire up ext4_readpage[s] to use mpage_readpage[s]
>   ext4: Enable encryption for subpage-sized blocks
>   fscrypt: remove struct fscrypt_ctx
> 
>  Documentation/filesystems/fscrypt.rst |   4 +-
>  fs/Kconfig                            |   3 +
>  fs/Makefile                           |   1 +
>  fs/buffer.c                           |  33 ++-
>  fs/crypto/bio.c                       |  18 --
>  fs/crypto/crypto.c                    |  89 +-------
>  fs/crypto/fscrypt_private.h           |   3 -
>  fs/ext4/Kconfig                       |   1 +
>  fs/ext4/Makefile                      |   2 +-
>  fs/ext4/inode.c                       |   5 +-
>  fs/ext4/readpage.c                    | 295 --------------------------
>  fs/ext4/super.c                       |   7 -
>  fs/f2fs/Kconfig                       |   1 +
>  fs/mpage.c                            |  24 ++-
>  fs/read_callbacks.c                   | 285 +++++++++++++++++++++++++
>  include/linux/buffer_head.h           |   2 +
>  include/linux/fscrypt.h               |  32 ---
>  include/linux/read_callbacks.h        |  48 +++++
>  18 files changed, 391 insertions(+), 462 deletions(-)
>  delete mode 100644 fs/ext4/readpage.c
>  create mode 100644 fs/read_callbacks.c
>  create mode 100644 include/linux/read_callbacks.h
> 
> 


-- 
chandan




      parent reply	other threads:[~2019-09-02  4:36 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-23 13:25 Chandan Rajendra
2019-08-23 13:25 ` [PATCH V5 1/7] buffer_head: Introduce BH_Read_Cb flag Chandan Rajendra
2019-08-23 13:25 ` [PATCH V5 2/7] FS: Introduce read callbacks Chandan Rajendra
2019-08-23 13:25 ` [PATCH V5 3/7] fs/mpage.c: Integrate " Chandan Rajendra
2019-08-23 13:25 ` [PATCH V5 4/7] fs/buffer.c: add decryption support via read_callbacks Chandan Rajendra
2019-08-23 13:25 ` [PATCH V5 5/7] ext4: Wire up ext4_readpage[s] to use mpage_readpage[s] Chandan Rajendra
2019-08-23 13:25 ` [PATCH V5 6/7] ext4: Enable encryption for subpage-sized blocks Chandan Rajendra
2019-08-23 13:25 ` [PATCH V5 7/7] fscrypt: remove struct fscrypt_ctx Chandan Rajendra
2019-09-02  4:38 ` Chandan Rajendra [this message]

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