iov_iter_bvec_advance(): don't bother with bvec_iter

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

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 4c658a2..c513146 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -846,17 +846,22 @@ 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)