Hi Chandan,
On Mon, Feb 12, 2018 at 03:13:41PM +0530, Chandan Rajendra wrote:
> With block size < page size, ext4_block_write_begin() can have up to two
> blocks to decrypt. Hence this commit invokes fscrypt_decrypt_block() for
> each of those blocks.
>
> Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
> ---
> fs/ext4/inode.c | 33 +++++++++++++++++++++++----------
> 1 file changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 69a4fd6..180dd2d 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1158,12 +1158,13 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
> unsigned to = from + len;
> struct inode *inode = page->mapping->host;
> unsigned block_start, block_end;
> - sector_t block;
> + sector_t block, page_blk_nr;
> int err = 0;
> unsigned blocksize = inode->i_sb->s_blocksize;
> unsigned bbits;
> struct buffer_head *bh, *head, *wait[2], **wait_bh = wait;
> bool decrypt = false;
> + int i;
>
> BUG_ON(!PageLocked(page));
> BUG_ON(from > PAGE_SIZE);
> @@ -1224,18 +1225,30 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
> /*
> * If we issued read requests, let them complete.
> */
> - while (wait_bh > wait) {
> - wait_on_buffer(*--wait_bh);
> - if (!buffer_uptodate(*wait_bh))
> + for (i = 0; &wait[i] < wait_bh; i++) {
> + wait_on_buffer(wait[i]);
> + if (!buffer_uptodate(wait[i]))
> err = -EIO;
> }
[...]
> + for (i = 0; &wait[i] < wait_bh; i++) {
> + int err2;
> +
> + --wait_bh;
> + block = page_blk_nr + (bh_offset(wait[i]) >> bbits);
> + err2 = fscrypt_decrypt_block(page->mapping->host, page,
> + wait[i]->b_size,
> + bh_offset(wait[i]),
> + block);
> + if (err2) {
> + clear_buffer_uptodate(wait[i]);
> + err = err2;
> + }
> + }
These are very confusing ways to iterate through an array, especially the second
loop which is actually going in reverse order (why?). Why not just use a
variable like 'nr_wait' for the number of valid buffer_head's like I had
suggested? Then you can just do 'for (i = 0; i < nr_wait; i++)'.
- Eric
