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Date:   Tue, 30 Apr 2019 22:10:38 +0100
From:   Jeremy Sowden <jeremy@...zel.net>
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, ebiggers@...nel.org, jaegeuk@...nel.org,
        yuchao0@...wei.com, hch@...radead.org
Subject: Re: [PATCH V2 03/13] fsverity: Add call back to decide if verity
 check has to be performed

On 2019-04-28, at 10:01:11 +0530, Chandan Rajendra wrote:
> Ext4 and F2FS store verity metadata in data extents (beyond
> inode->i_size) associated with a file. But other filesystems might
> choose alternative means to store verity metadata. Hence this commit
> adds a callback function pointer to 'struct fsverity_operations' to
> help in deciding if verity operation needs to performed against a
> page-cache page holding file data.
> 
> Signed-off-by: Chandan Rajendra <chandan@...ux.ibm.com>
> ---
>  fs/ext4/super.c          | 6 ++++++
>  fs/f2fs/super.c          | 6 ++++++
>  fs/read_callbacks.c      | 4 +++-
>  include/linux/fsverity.h | 1 +
>  4 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index aba724f82cc3..63d73b360f1d 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1428,10 +1428,16 @@ static struct page *ext4_read_verity_metadata_page(struct inode *inode,
>  	return read_mapping_page(inode->i_mapping, index, NULL);
>  }
>  
> +static bool ext4_verity_required(struct inode *inode, pgoff_t index)
> +{
> +	return index < (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +}
> +
>  static const struct fsverity_operations ext4_verityops = {
>  	.set_verity		= ext4_set_verity,
>  	.get_metadata_end	= ext4_get_verity_metadata_end,
>  	.read_metadata_page	= ext4_read_verity_metadata_page,
> +	.verity_required	= ext4_verity_required,
>  };
>  #endif /* CONFIG_FS_VERITY */
>  
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 2f75f06c784a..cd1299e1f92d 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2257,10 +2257,16 @@ static struct page *f2fs_read_verity_metadata_page(struct inode *inode,
>  	return read_mapping_page(inode->i_mapping, index, NULL);
>  }
>  
> +static bool f2fs_verity_required(struct inode *inode, pgoff_t index)
> +{
> +	return index < (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +}
> +
>  static const struct fsverity_operations f2fs_verityops = {
>  	.set_verity		= f2fs_set_verity,
>  	.get_metadata_end	= f2fs_get_verity_metadata_end,
>  	.read_metadata_page	= f2fs_read_verity_metadata_page,
> +	.verity_required	= f2fs_verity_required,
>  };
>  #endif /* CONFIG_FS_VERITY */
>  
> diff --git a/fs/read_callbacks.c b/fs/read_callbacks.c
> index b6d5b95e67d7..6dea54b0baa9 100644
> --- a/fs/read_callbacks.c
> +++ b/fs/read_callbacks.c
> @@ -86,7 +86,9 @@ struct read_callbacks_ctx *get_read_callbacks_ctx(struct inode *inode,
>  		read_callbacks_steps |= 1 << STEP_DECRYPT;
>  #ifdef CONFIG_FS_VERITY
>  	if (inode->i_verity_info != NULL &&
> -		(index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
> +		((inode->i_sb->s_vop->verity_required
> +			&& inode->i_sb->s_vop->verity_required(inode, index))
> +			|| (inode->i_sb->s_vop->verity_required == NULL)))

I think this is a bit easier to follow:

		(inode->i_sb->s_vop->verity_required == NULL || 
			inode->i_sb->s_vop->verity_required(inode, index)))

>  		read_callbacks_steps |= 1 << STEP_VERITY;
>  #endif
>  	if (read_callbacks_steps) {
> diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
> index 7c33b42abf1b..b83712d6c79a 100644
> --- a/include/linux/fsverity.h
> +++ b/include/linux/fsverity.h
> @@ -18,6 +18,7 @@ struct fsverity_operations {
>  	int (*set_verity)(struct inode *inode, loff_t data_i_size);
>  	int (*get_metadata_end)(struct inode *inode, loff_t *metadata_end_ret);
>  	struct page *(*read_metadata_page)(struct inode *inode, pgoff_t index);
> +	bool (*verity_required)(struct inode *inode, pgoff_t index);
>  };
>  
>  #ifdef CONFIG_FS_VERITY
> -- 
> 2.19.1
>
>

J.

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