[PATCH v2 21/51] block: implement sp version of bvec iterator helpers

Ming Lei
2017-06-26T12:10:04Z

This patch implements singlepage version of the following
3 helpers:
- bvec_iter_offset_sp()
- bvec_iter_len_sp()
- bvec_iter_page_sp()

So that one multipage bvec can be splited to singlepage
bvec, and make users of current bvec iterator happy.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/bvec.h | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index f52587e283d4..61632e9db3b8 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -22,6 +22,7 @@

#include <linux/kernel.h>
#include <linux/bug.h>
+#include <linux/mm.h>

/*
* What is multipage bvecs(segment)?
@@ -95,14 +96,25 @@ struct bvec_iter {
#define bvec_iter_offset_mp(bvec, iter) \
(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)

+#define bvec_iter_page_idx_mp(bvec, iter) \
+ (bvec_iter_offset_mp((bvec), (iter)) / PAGE_SIZE)
+
+
/*
* <page, offset,length> of singlepage(sp) segment.
*
* This helpers will be implemented for building sp bvec in flight.
*/
-#define bvec_iter_offset_sp(bvec, iter) bvec_iter_offset_mp((bvec), (iter))
-#define bvec_iter_len_sp(bvec, iter) bvec_iter_len_mp((bvec), (iter))
-#define bvec_iter_page_sp(bvec, iter) bvec_iter_page_mp((bvec), (iter))
+#define bvec_iter_offset_sp(bvec, iter) \
+ (bvec_iter_offset_mp((bvec), (iter)) % PAGE_SIZE)
+
+#define bvec_iter_len_sp(bvec, iter) \
+ min_t(unsigned, bvec_iter_len_mp((bvec), (iter)), \
+ (PAGE_SIZE - (bvec_iter_offset_sp((bvec), (iter)))))
+
+#define bvec_iter_page_sp(bvec, iter) \
+ nth_page(bvec_iter_page_mp((bvec), (iter)), \
+ bvec_iter_page_idx_mp((bvec), (iter)))

/* current interfaces support sp style at default */
#define bvec_iter_page(bvec, iter) bvec_iter_page_sp((bvec), (iter))
--
2.9.4