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csum_and_copy_to_iter(): massage into form closer to csum_and_copy_from_iter()

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Namely, have off counted starting from 0 rather than from csstate->off.
To compensate we need to shift the initial value (csstate->sum) (rotate
by 8 bits, as usual for csum) and do the same after we are finished adding
the pieces up.

What we get out of that is a bit more redundancy in our variables - from
is always equal to addr + off, which will be useful several commits down
the road.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2021-06-05 10:19:30 -04:00
parent f0b65f39ac
commit 594e450b3f
2 changed files with 13 additions and 11 deletions
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lib/iov_iter.c
+4 -4
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@@ -1781,8 +1781,8 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
if (unlikely(iov_iter_is_pipe(i)))
return csum_and_copy_to_pipe_iter(addr, bytes, _csstate, i);
sum = csstate->csum;
off = csstate->off;
sum = csum_shift(csstate->csum, csstate->off);
off = 0;
if (unlikely(iov_iter_is_discard(i))) {
WARN_ON(1); /* for now */
return 0;
@@ -1817,8 +1817,8 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
off += v.bv_len;
})
)
csstate->csum = sum;
csstate->off = off;
csstate->csum = csum_shift(sum, csstate->off);
csstate->off += bytes;
return bytes;
}
EXPORT_SYMBOL(csum_and_copy_to_iter);