1 files changed, 93 insertions, 30 deletions

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 02c73c6aa805..f6275c4da13a 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -23,6 +23,7 @@
 #include <linux/kernel.h>
 #include <linux/bug.h>
 #include <linux/errno.h>
+#include <linux/mm.h>
 
 /*
  * was unsigned short, but we might as well be ready for > 64kB I/O pages
@@ -44,22 +45,56 @@ struct bvec_iter {
 						   current bvec */
 };
 
+struct bvec_iter_all {
+	struct bio_vec	bv;
+	int		idx;
+	unsigned	done;
+};
+
+static inline struct page *bvec_nth_page(struct page *page, int idx)
+{
+	return idx == 0 ? page : nth_page(page, idx);
+}
+
 /*
  * various member access, note that bio_data should of course not be used
  * on highmem page vectors
  */
 #define __bvec_iter_bvec(bvec, iter)	(&(bvec)[(iter).bi_idx])
 
-#define bvec_iter_page(bvec, iter)				\
+/* multi-page (mp_bvec) helpers */
+#define mp_bvec_iter_page(bvec, iter)				\
 	(__bvec_iter_bvec((bvec), (iter))->bv_page)
 
-#define bvec_iter_len(bvec, iter)				\
+#define mp_bvec_iter_len(bvec, iter)				\
 	min((iter).bi_size,					\
 	    __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
 
-#define bvec_iter_offset(bvec, iter)				\
+#define mp_bvec_iter_offset(bvec, iter)				\
 	(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
 
+#define mp_bvec_iter_page_idx(bvec, iter)			\
+	(mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
+
+#define mp_bvec_iter_bvec(bvec, iter)				\
+((struct bio_vec) {						\
+	.bv_page	= mp_bvec_iter_page((bvec), (iter)),	\
+	.bv_len		= mp_bvec_iter_len((bvec), (iter)),	\
+	.bv_offset	= mp_bvec_iter_offset((bvec), (iter)),	\
+})
+
+/* For building single-page bvec in flight */
+ #define bvec_iter_offset(bvec, iter)				\
+	(mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
+
+#define bvec_iter_len(bvec, iter)				\
+	min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),		\
+	      PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
+
+#define bvec_iter_page(bvec, iter)				\
+	bvec_nth_page(mp_bvec_iter_page((bvec), (iter)),		\
+		      mp_bvec_iter_page_idx((bvec), (iter)))
+
 #define bvec_iter_bvec(bvec, iter)				\
 ((struct bio_vec) {						\
 	.bv_page	= bvec_iter_page((bvec), (iter)),	\
@@ -77,14 +112,15 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
 	}
 
 	while (bytes) {
-		unsigned iter_len = bvec_iter_len(bv, *iter);
-		unsigned len = min(bytes, iter_len);
+		const struct bio_vec *cur = bv + iter->bi_idx;
+		unsigned len = min3(bytes, iter->bi_size,
+				    cur->bv_len - iter->bi_bvec_done);
 
 		bytes -= len;
 		iter->bi_size -= len;
 		iter->bi_bvec_done += len;
 
-		if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
+		if (iter->bi_bvec_done == cur->bv_len) {
 			iter->bi_bvec_done = 0;
 			iter->bi_idx++;
 		}
@@ -92,30 +128,6 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
 	return true;
 }
 
-static inline bool bvec_iter_rewind(const struct bio_vec *bv,
-				     struct bvec_iter *iter,
-				     unsigned int bytes)
-{
-	while (bytes) {
-		unsigned len = min(bytes, iter->bi_bvec_done);
-
-		if (iter->bi_bvec_done == 0) {
-			if (WARN_ONCE(iter->bi_idx == 0,
-				      "Attempted to rewind iter beyond "
-				      "bvec's boundaries\n")) {
-				return false;
-			}
-			iter->bi_idx--;
-			iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;
-			continue;
-		}
-		bytes -= len;
-		iter->bi_size += len;
-		iter->bi_bvec_done -= len;
-	}
-	return true;
-}
-
 #define for_each_bvec(bvl, bio_vec, iter, start)			\
 	for (iter = (start);						\
 	     (iter).bi_size &&						\
@@ -131,4 +143,55 @@ static inline bool bvec_iter_rewind(const struct bio_vec *bv,
 	.bi_bvec_done	= 0,						\
 }
 
+static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
+{
+	iter_all->bv.bv_page = NULL;
+	iter_all->done = 0;
+
+	return &iter_all->bv;
+}
+
+static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
+					struct bvec_iter_all *iter_all)
+{
+	struct bio_vec *bv = &iter_all->bv;
+
+	if (bv->bv_page) {
+		bv->bv_page = nth_page(bv->bv_page, 1);
+		bv->bv_offset = 0;
+	} else {
+		bv->bv_page = bvec->bv_page;
+		bv->bv_offset = bvec->bv_offset;
+	}
+	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
+			   bvec->bv_len - iter_all->done);
+}
+
+/*
+ * Get the last single-page segment from the multi-page bvec and store it
+ * in @seg
+ */
+static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
+					struct bio_vec *seg)
+{
+	unsigned total = bvec->bv_offset + bvec->bv_len;
+	unsigned last_page = (total - 1) / PAGE_SIZE;
+
+	seg->bv_page = bvec_nth_page(bvec->bv_page, last_page);
+
+	/* the whole segment is inside the last page */
+	if (bvec->bv_offset >= last_page * PAGE_SIZE) {
+		seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
+		seg->bv_len = bvec->bv_len;
+	} else {
+		seg->bv_offset = 0;
+		seg->bv_len = total - last_page * PAGE_SIZE;
+	}
+}
+
+#define mp_bvec_for_each_page(pg, bv, i)				\
+	for (i = (bv)->bv_offset / PAGE_SIZE;				\
+		(i <= (((bv)->bv_offset + (bv)->bv_len - 1) / PAGE_SIZE)) && \
+		(pg = bvec_nth_page((bv)->bv_page, i)); i += 1)
+
 #endif /* __LINUX_BVEC_ITER_H */