[PATCH v3 5/7] iov_iter: optimise bvec iov_iter_advance()

Pavel Begunkov
2021-01-09T16:08:53Z

iov_iter_advance() is heavily used, but implemented through generic
means. For bvecs there is a specifically crafted function for that, so
use bvec_iter_advance() instead, it's faster and slimmer.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
lib/iov_iter.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7de304269641..9b1c109dc8a9 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1065,6 +1065,21 @@ static void pipe_advance(struct iov_iter *i, size_t size)
pipe_truncate(i);
}

+static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
+{
+ struct bvec_iter bi;
+
+ bi.bi_size = i->count;
+ bi.bi_bvec_done = i->iov_offset;
+ bi.bi_idx = 0;
+ bvec_iter_advance(i->bvec, &bi, size);
+
+ i->bvec += bi.bi_idx;
+ i->nr_segs -= bi.bi_idx;
+ i->count = bi.bi_size;
+ i->iov_offset = bi.bi_bvec_done;
+}
+
void iov_iter_advance(struct iov_iter *i, size_t size)
{
if (unlikely(iov_iter_is_pipe(i))) {
@@ -1075,6 +1090,10 @@ void iov_iter_advance(struct iov_iter *i, size_t size)
i->count -= size;
return;
}
+ if (iov_iter_is_bvec(i)) {
+ iov_iter_bvec_advance(i, size);
+ return;
+ }
iterate_and_advance(i, size, v, 0, 0, 0)
}
EXPORT_SYMBOL(iov_iter_advance);
--
2.24.0