On Fri, Jan 12, 2018 at 07:41:25PM +0530, Chandan Rajendra wrote:
> With block size < page size, ext4_block_write_begin() may have two
> blocks to decrypt. Hence this commit invokes fscrypt_decrypt_page() for
> those blocks.
>
> Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
> ---
> fs/ext4/inode.c | 29 +++++++++++++++++++++--------
> 1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 6f6589e..d3baa15 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);
> @@ -1224,16 +1225,28 @@ 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;
> }
> - if (unlikely(err))
> + if (unlikely(err)) {
> page_zero_new_buffers(page, from, to);
> - else if (decrypt)
> - err = fscrypt_decrypt_page(page->mapping->host, page,
> - PAGE_SIZE, 0, page->index);
> + } else if (decrypt) {
> + page_blk_nr = (sector_t)page->index << (PAGE_SHIFT - bbits);
> +
> + while (wait_bh > wait) {
> + --wait_bh;
> + block = page_blk_nr + (bh_offset(*wait_bh) >> bbits);
> + err = fscrypt_decrypt_page(page->mapping->host, page,
> + (*wait_bh)->b_size,
> + bh_offset(*wait_bh),
> + block);
> + if (err)
> + break;
> + }
> + }
> +
> return err;
Iterating through the 'wait' array once by index and once by pointer is
confusing. Why not do it just by index? e.g.
int nr_wait = 0;
int i;
...
wait[nr_wait++] = bh;
...
for (i = 0; i < nr_wait; i++) {
wait_on_buffer(wait[i]);
...
}
for (i = 0; i < nr_wait; i++) {
...
fscrypt_decrypt_block(...)
...
}
Also, you are leaving the buffers uptodate() if the decryption fails, which is
wrong. It is an existing bug even in the block_size == PAGE_SIZE case, but it
should be fixed if possible.
Eric
