From: Al Viro
> Sent: 21 July 2020 21:26
> Preparation for the change of calling conventions; right now all
> callers pass 0 as initial sum. Passing 0xffffffff instead yields
> the values comparable mod 0xffff and guarantees that 0 will not
> be returned on success.
>
> Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
> ---
> lib/iov_iter.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 7405922caaec..d5b7e204fea6 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1451,7 +1451,7 @@ size_t csum_and_copy_from_iter(void *addr, size_t
> bytes, __wsum *csum,
> int err = 0;
> next = csum_and_copy_from_user(v.iov_base,
> (to += v.iov_len) - v.iov_len,
> - v.iov_len, 0, &err);
> + v.iov_len, ~0U, &err);
> if (!err) {
> sum = csum_block_add(sum, next, off);
> off += v.iov_len;
Can't you remove the csum_block_add() by passing the
old 'sum' in instead of the ~0U ?
You'll need to keep track of whether the buffer fragment
is odd/even aligned.
After an odd length fragment a bswap32() or 8 bit rotate will
fix things (and maybe one right at the end).
David
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