linux-kernel - [PATCH v4 4/8] iov_iter: use bvec iterator to implement iterate

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Message-Id: <1460634438-26530-5-git-send-email-ming.lei@canonical.com>
Date:	Thu, 14 Apr 2016 19:46:57 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org
Cc:	linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Ming Lei <ming.lei@...onical.com>
Subject: [PATCH v4 4/8] iov_iter: use bvec iterator to implement iterate_bvec()

bvec has provided one iterator already, so not necessary
to reinvent a new wheel for this job.

Signed-off-by: Ming Lei <ming.lei@...onical.com>
---
 lib/iov_iter.c | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5fecddc..c8691ac 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -57,35 +57,25 @@
 }
 
 #define iterate_bvec(i, n, __v, __p, skip, STEP) {	\
-	size_t wanted = n;				\
+	struct bvec_iter __bi, __start;			\
+	__start.bi_size = n;				\
+	__start.bi_bvec_done = skip;			\
+	__start.bi_idx = 0;				\
 	__p = i->bvec;					\
-	__v.bv_len = min_t(size_t, n, __p->bv_len - skip);	\
-	if (likely(__v.bv_len)) {			\
-		__v.bv_page = __p->bv_page;		\
-		__v.bv_offset = __p->bv_offset + skip; 	\
+	for_each_bvec(__v, __p, __bi, __start) {	\
 		(void)(STEP);				\
-		skip += __v.bv_len;			\
-		n -= __v.bv_len;			\
 	}						\
-	while (unlikely(n)) {				\
-		__p++;					\
-		__v.bv_len = min_t(size_t, n, __p->bv_len);	\
-		if (unlikely(!__v.bv_len))		\
-			continue;			\
-		__v.bv_page = __p->bv_page;		\
-		__v.bv_offset = __p->bv_offset;		\
-		(void)(STEP);				\
+	if (!__bi.bi_idx)				\
+		skip += __v.bv_len;			\
+	else						\
 		skip = __v.bv_len;			\
-		n -= __v.bv_len;			\
-	}						\
-	n = wanted;					\
 }
 
 #define iterate_all_kinds(i, n, v, I, B, K) {			\
 	size_t skip = i->iov_offset;				\
 	if (unlikely(i->type & ITER_BVEC)) {			\
 		const struct bio_vec *bvec;			\
-		struct bio_vec v;				\
+		struct bio_vec v = { 0 };			\
 		iterate_bvec(i, n, v, bvec, skip, (B))		\
 	} else if (unlikely(i->type & ITER_KVEC)) {		\
 		const struct kvec *kvec;			\
@@ -102,7 +92,7 @@
 	size_t skip = i->iov_offset;				\
 	if (unlikely(i->type & ITER_BVEC)) {			\
 		const struct bio_vec *bvec;			\
-		struct bio_vec v;				\
+		struct bio_vec v = { 0 };			\
 		iterate_bvec(i, n, v, bvec, skip, (B))		\
 		if (skip == bvec->bv_len) {			\
 			bvec++;					\
-- 
1.9.1