Re: [PATCH V2 11/13] ext4: Compute logical block and the page range to be encrypted

[Eric Biggers <ebiggers@kernel.org>]

On Sun, Apr 28, 2019 at 10:01:19AM +0530, Chandan Rajendra wrote:
> For subpage-sized blocks, the initial logical block number mapped by a
> page can be different from page->index. Hence this commit adds code to
> compute the first logical block mapped by the page and also the page
> range to be encrypted.
> 
> Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> ---
>  fs/ext4/page-io.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 3e9298e6a705..75485ee9e800 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -418,6 +418,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
>  {
>  	struct page *data_page = NULL;
>  	struct inode *inode = page->mapping->host;
> +	u64 page_blk;
>  	unsigned block_start;
>  	struct buffer_head *bh, *head;
>  	int ret = 0;
> @@ -478,10 +479,14 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
>  
>  	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode) && nr_to_submit) {
>  		gfp_t gfp_flags = GFP_NOFS;
> +		unsigned int page_bytes;
> +

page_blk should be declared here, just after page_bytes.

> +		page_bytes = round_up(len, i_blocksize(inode));
> +		page_blk = page->index << (PAGE_SHIFT - inode->i_blkbits);

Although block numbers are 32-bit in ext4, if you're going to make 'page_blk' a
u64 anyway, then for consistency page->index should be cast to u64 here.

>  
>  	retry_encrypt:
> -		data_page = fscrypt_encrypt_page(inode, page, PAGE_SIZE, 0,
> -						page->index, gfp_flags);
> +		data_page = fscrypt_encrypt_page(inode, page, page_bytes, 0,
> +						page_blk, gfp_flags);
>  		if (IS_ERR(data_page)) {
>  			ret = PTR_ERR(data_page);
>  			if (ret == -ENOMEM && wbc->sync_mode == WB_SYNC_ALL) {
> -- 
> 2.19.1
>