Re: [PATCH v2 19/20] btrfs: encrypt normal file extent data if appropriate

[Josef Bacik <josef@toxicpanda.com>]

On Mon, Sep 05, 2022 at 08:35:34PM -0400, Sweet Tea Dorminy wrote:
> From: Omar Sandoval <osandov@osandov.com>
> 
> Add in the necessary calls to encrypt and decrypt data to achieve
> encryption of normal data.
>

A little more description of what these bounce pages are and what we're doing
with them.
 
> Signed-off-by: Omar Sandoval <osandov@osandov.com>
> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
> ---
>  fs/btrfs/extent_io.c    | 56 ++++++++++++++++++++++++++++++++++++-----
>  fs/btrfs/file-item.c    |  9 +++++--
>  fs/btrfs/fscrypt.c      | 23 ++++++++++++++++-
>  fs/btrfs/tree-checker.c | 11 +++++---
>  4 files changed, 87 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index a467a7553bd9..8adcee599844 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -183,6 +183,7 @@ static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
>  {
>  	struct bio *bio;
>  	struct bio_vec *bv;
> +	struct page *first_page;
>  	struct inode *inode;
>  	int mirror_num;
>  
> @@ -191,13 +192,17 @@ static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
>  
>  	bio = bio_ctrl->bio;
>  	bv = bio_first_bvec_all(bio);
> -	inode = bv->bv_page->mapping->host;
> +	first_page = bio_first_page_all(bio);
> +	if (fscrypt_is_bounce_page(first_page))
> +		inode = fscrypt_pagecache_page(first_page)->mapping->host;
> +	else
> +		inode = first_page->mapping->host;
>  	mirror_num = bio_ctrl->mirror_num;
>  
>  	/* Caller should ensure the bio has at least some range added */
>  	ASSERT(bio->bi_iter.bi_size);
>  
> -	btrfs_bio(bio)->file_offset = page_offset(bv->bv_page) + bv->bv_offset;
> +	btrfs_bio(bio)->file_offset = page_offset(first_page) + bv->bv_offset;
>  
>  	if (!is_data_inode(inode))
>  		btrfs_submit_metadata_bio(inode, bio, mirror_num);
> @@ -2810,9 +2815,19 @@ static void end_bio_extent_writepage(struct btrfs_bio *bbio)
>  	ASSERT(!bio_flagged(bio, BIO_CLONED));
>  	bio_for_each_segment_all(bvec, bio, iter_all) {
>  		struct page *page = bvec->bv_page;
> -		struct inode *inode = page->mapping->host;
> -		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> -		const u32 sectorsize = fs_info->sectorsize;
> +		struct inode *inode;
> +		struct btrfs_fs_info *fs_info;
> +		u32 sectorsize;
> +		struct page *bounce_page = NULL;
> +
> +		if (fscrypt_is_bounce_page(page)) {
> +			bounce_page = page;
> +			page = fscrypt_pagecache_page(bounce_page);
> +		}
> +
> +		inode = page->mapping->host;
> +		fs_info = btrfs_sb(inode->i_sb);
> +		sectorsize = fs_info->sectorsize;
>  
>  		/* Our read/write should always be sector aligned. */
>  		if (!IS_ALIGNED(bvec->bv_offset, sectorsize))
> @@ -2833,7 +2848,7 @@ static void end_bio_extent_writepage(struct btrfs_bio *bbio)
>  		}
>  
>  		end_extent_writepage(page, error, start, end);
> -
> +		fscrypt_free_bounce_page(bounce_page);
>  		btrfs_page_clear_writeback(fs_info, page, start, bvec->bv_len);
>  	}
>  
> @@ -3029,6 +3044,17 @@ static void end_bio_extent_readpage(struct btrfs_bio *bbio)
>  			}
>  		}
>  
> +		if (likely(uptodate)) {
> +			if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
> +				int ret = fscrypt_decrypt_pagecache_blocks(page,
> +									   bvec->bv_len,
> +									   bvec->bv_offset);
> +				if (ret) {
> +					error_bitmap = (unsigned int) -1;
> +					uptodate = false;
> +					}

This thing.  Thanks,

Josef