[PATCH 11/44] iov_iter_bvec_advance(): don't bother with bvec_iter

[Al Viro <viro@zeniv.linux.org.uk>]

do what we do for iovec/kvec; that ends up generating better code,
AFAICS.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 lib/iov_iter.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 8275b28e886b..93ceb13ec7b5 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -870,17 +870,22 @@ static void pipe_advance(struct iov_iter *i, size_t size)
 
 static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
 {
-	struct bvec_iter bi;
+	const struct bio_vec *bvec, *end;
 
-	bi.bi_size = i->count;
-	bi.bi_bvec_done = i->iov_offset;
-	bi.bi_idx = 0;
-	bvec_iter_advance(i->bvec, &bi, size);
+	if (!i->count)
+		return;
+	i->count -= size;
+
+	size += i->iov_offset;
 
-	i->bvec += bi.bi_idx;
-	i->nr_segs -= bi.bi_idx;
-	i->count = bi.bi_size;
-	i->iov_offset = bi.bi_bvec_done;
+	for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) {
+		if (likely(size < bvec->bv_len))
+			break;
+		size -= bvec->bv_len;
+	}
+	i->iov_offset = size;
+	i->nr_segs -= bvec - i->bvec;
+	i->bvec = bvec;
 }
 
 static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
-- 
2.30.2