[PATCH v2 02/12] csum_and_copy_to_iter(): handle ITER_DISCARD

Al Viro
2022-10-28T02:34:21Z

Not hard to implement - we are not copying anything here, so
csum_and_memcpy() is not usable, but calculating a checksum
of source directly is trivial...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
lib/iov_iter.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index e9a8fc9ee8ee..020e009d71c5 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1549,8 +1549,12 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
__wsum sum, next;

if (unlikely(iov_iter_is_discard(i))) {
- WARN_ON(1); /* for now */
- return 0;
+ // can't use csum_memcpy() for that one - data is not copied
+ csstate->csum = csum_block_add(csstate->csum,
+ csum_partial(addr, bytes, 0),
+ csstate->off);
+ csstate->off += bytes;
+ return bytes;
}

sum = csum_shift(csstate->csum, csstate->off);
--
2.30.2