saner calling conventions for csum_and_copy_..._user()

All callers of these primitives will
	* discard anything we might've copied in case of error
	* ignore the csum value in case of error
	* always pass 0xffffffff as the initial sum, so the
resulting csum value (in case of success, that is) will never be 0.

That suggest the following calling conventions:
	* don't pass err_ptr - just return 0 on error.
	* don't bother with zeroing destination, etc. in case of error
	* don't pass the initial sum - just use 0xffffffff.

This commit does the minimal conversion in the instances of csum_and_copy_...();
the changes of actual asm code behind them are done later in the series.
Note that this asm code is often shared with csum_partial_copy_nocheck();
the difference is that csum_partial_copy_nocheck() passes 0 for initial
sum while csum_and_copy_..._user() pass 0xffffffff.  Fortunately, we are
free to pass 0xffffffff in all cases and subsequent patches will use that
freedom without any special comments.

A part that could be split off: parisc and uml/i386 claimed to have
csum_and_copy_to_user() instances of their own, but those were identical
to the generic one, so we simply drop them.  Not sure if it's worth
a separate commit...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 8 insertions, 11 deletions

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 437fbc14c972..ccb247faf79b 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1449,15 +1449,14 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 		return 0;
 	}
 	iterate_and_advance(i, bytes, v, ({
-		int err = 0;
 		next = csum_and_copy_from_user(v.iov_base,
 					       (to += v.iov_len) - v.iov_len,
-					       v.iov_len, ~0U, &err);
-		if (!err) {
+					       v.iov_len);
+		if (next) {
 			sum = csum_block_add(sum, next, off);
 			off += v.iov_len;
 		}
-		err ? v.iov_len : 0;
+		next ? 0 : v.iov_len;
 	}), ({
 		char *p = kmap_atomic(v.bv_page);
 		sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
@@ -1491,11 +1490,10 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
 	if (unlikely(i->count < bytes))
 		return false;
 	iterate_all_kinds(i, bytes, v, ({
-		int err = 0;
 		next = csum_and_copy_from_user(v.iov_base,
 					       (to += v.iov_len) - v.iov_len,
-					       v.iov_len, ~0U, &err);
-		if (err)
+					       v.iov_len);
+		if (!next)
 			return false;
 		sum = csum_block_add(sum, next, off);
 		off += v.iov_len;
@@ -1537,15 +1535,14 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump,
 		return 0;
 	}
 	iterate_and_advance(i, bytes, v, ({
-		int err = 0;
 		next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
 					     v.iov_base,
-					     v.iov_len, ~0U, &err);
-		if (!err) {
+					     v.iov_len);
+		if (next) {
 			sum = csum_block_add(sum, next, off);
 			off += v.iov_len;
 		}
-		err ? v.iov_len : 0;
+		next ? 0 : v.iov_len;
 	}), ({
 		char *p = kmap_atomic(v.bv_page);
 		sum = csum_and_memcpy(p + v.bv_offset,