Re: [PATCH V2 02/13] Consolidate "read callbacks" into a new file

[Eric Biggers <ebiggers@kernel.org>]

On Sun, Apr 28, 2019 at 10:01:10AM +0530, Chandan Rajendra wrote:
> The "read callbacks" code is used by both Ext4 and F2FS. Hence to
> remove duplicity, this commit moves the code into
> include/linux/read_callbacks.h and fs/read_callbacks.c.
> 
> The corresponding decrypt and verity "work" functions have been moved
> inside fscrypt and fsverity sources. With these in place, the read
> callbacks code now has to just invoke enqueue functions provided by
> fscrypt and fsverity.
> 
> Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> ---
>  fs/Kconfig                     |   4 +
>  fs/Makefile                    |   4 +
>  fs/crypto/Kconfig              |   1 +
>  fs/crypto/bio.c                |  23 ++---
>  fs/crypto/crypto.c             |  17 +--
>  fs/crypto/fscrypt_private.h    |   3 +
>  fs/ext4/ext4.h                 |   2 -
>  fs/ext4/readpage.c             | 183 +++++----------------------------
>  fs/ext4/super.c                |   9 +-
>  fs/f2fs/data.c                 | 148 ++++----------------------
>  fs/f2fs/super.c                |   9 +-
>  fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
>  fs/verity/Kconfig              |   1 +
>  fs/verity/verify.c             |  12 +++
>  include/linux/fscrypt.h        |  20 +---
>  include/linux/read_callbacks.h |  21 ++++
>  16 files changed, 251 insertions(+), 342 deletions(-)
>  create mode 100644 fs/read_callbacks.c
>  create mode 100644 include/linux/read_callbacks.h
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 97f9eb8df713..03084f2dbeaf 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -308,6 +308,10 @@ config NFS_COMMON
>  	depends on NFSD || NFS_FS || LOCKD
>  	default y
>  
> +config FS_READ_CALLBACKS
> +       bool
> +       default n
> +
>  source "net/sunrpc/Kconfig"
>  source "fs/ceph/Kconfig"
>  source "fs/cifs/Kconfig"

This shouldn't be under the 'if NETWORK_FILESYSTEMS' block, since it has nothing
to do with network filesystems.  When trying to compile this I got:

	WARNING: unmet direct dependencies detected for FS_READ_CALLBACKS
	  Depends on [n]: NETWORK_FILESYSTEMS [=n]
	  Selected by [y]:
	  - FS_ENCRYPTION [=y]
	  - FS_VERITY [=y]

Perhaps put it just below FS_IOMAP?

> diff --git a/fs/Makefile b/fs/Makefile
> index 9dd2186e74b5..e0c0fce8cf40 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -21,6 +21,10 @@ else
>  obj-y +=	no-block.o
>  endif
>  
> +ifeq ($(CONFIG_FS_READ_CALLBACKS),y)
> +obj-y +=	read_callbacks.o
> +endif
> +
>  obj-$(CONFIG_PROC_FS) += proc_namespace.o
>  
>  obj-y				+= notify/
> diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> index f0de238000c0..163c328bcbd4 100644
> --- a/fs/crypto/Kconfig
> +++ b/fs/crypto/Kconfig
> @@ -8,6 +8,7 @@ config FS_ENCRYPTION
>  	select CRYPTO_CTS
>  	select CRYPTO_SHA256
>  	select KEYS
> +	select FS_READ_CALLBACKS
>  	help
>  	  Enable encryption of files and directories.  This
>  	  feature is similar to ecryptfs, but it is more memory

This selection needs to be conditional on BLOCK.

	select FS_READ_CALLBACKS if BLOCK

Otherwise, building without BLOCK and with UBIFS encryption support fails.

	fs/read_callbacks.c: In function ‘end_read_callbacks’:
	fs/read_callbacks.c:34:23: error: storage size of ‘iter_all’ isn’t known
	  struct bvec_iter_all iter_all;
			       ^~~~~~~~
	fs/read_callbacks.c:37:20: error: dereferencing pointer to incomplete type ‘struct buffer_head’
	   if (!PageError(bh->b_page))

	[...]

- Eric