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csum_and_copy_to_iter(): handle ITER_DISCARD

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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>
This commit is contained in:
Al Viro 2022-09-15 20:20:59 -04:00
parent 40a86061a5
commit c67f1fd2b2
1 changed files with 6 additions and 2 deletions
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8
lib/iov_iter.c
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@ -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);