From 9b696229aa7de356675a938c6c8a70b46085ed66 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Wed, 5 Oct 2016 10:40:39 -0400
Subject: [PATCH] dm persistent data: add cursor skip functions to the cursor
 APIs

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
 drivers/md/persistent-data/dm-array.c  | 21 ++++++++++++++++
 drivers/md/persistent-data/dm-array.h  |  1 +
 drivers/md/persistent-data/dm-bitset.c | 35 ++++++++++++++++++++++++++
 drivers/md/persistent-data/dm-bitset.h |  1 +
 drivers/md/persistent-data/dm-btree.c  | 11 ++++++++
 drivers/md/persistent-data/dm-btree.h  |  1 +
 6 files changed, 70 insertions(+)

diff --git a/drivers/md/persistent-data/dm-array.c b/drivers/md/persistent-data/dm-array.c
index 7938cd21fa4c..185dc60360b5 100644
--- a/drivers/md/persistent-data/dm-array.c
+++ b/drivers/md/persistent-data/dm-array.c
@@ -976,6 +976,27 @@ int dm_array_cursor_next(struct dm_array_cursor *c)
 }
 EXPORT_SYMBOL_GPL(dm_array_cursor_next);
 
+int dm_array_cursor_skip(struct dm_array_cursor *c, uint32_t count)
+{
+	int r;
+
+	do {
+		uint32_t remaining = le32_to_cpu(c->ab->nr_entries) - c->index;
+
+		if (count < remaining) {
+			c->index += count;
+			return 0;
+		}
+
+		count -= remaining;
+		r = dm_array_cursor_next(c);
+
+	} while (!r);
+
+	return r;
+}
+EXPORT_SYMBOL_GPL(dm_array_cursor_skip);
+
 void dm_array_cursor_get_value(struct dm_array_cursor *c, void **value_le)
 {
 	*value_le = element_at(c->info, c->ab, c->index);
diff --git a/drivers/md/persistent-data/dm-array.h b/drivers/md/persistent-data/dm-array.h
index 27ee49a55473..d7d2d579c662 100644
--- a/drivers/md/persistent-data/dm-array.h
+++ b/drivers/md/persistent-data/dm-array.h
@@ -207,6 +207,7 @@ void dm_array_cursor_end(struct dm_array_cursor *c);
 
 uint32_t dm_array_cursor_index(struct dm_array_cursor *c);
 int dm_array_cursor_next(struct dm_array_cursor *c);
+int dm_array_cursor_skip(struct dm_array_cursor *c, uint32_t count);
 
 /*
  * value_le is only valid while the cursor points at the current value.
diff --git a/drivers/md/persistent-data/dm-bitset.c b/drivers/md/persistent-data/dm-bitset.c
index fbf8d9bc4d15..b7208d82e748 100644
--- a/drivers/md/persistent-data/dm-bitset.c
+++ b/drivers/md/persistent-data/dm-bitset.c
@@ -273,6 +273,41 @@ int dm_bitset_cursor_next(struct dm_bitset_cursor *c)
 }
 EXPORT_SYMBOL_GPL(dm_bitset_cursor_next);
 
+int dm_bitset_cursor_skip(struct dm_bitset_cursor *c, uint32_t count)
+{
+	int r;
+	__le64 *value;
+	uint32_t nr_array_skip;
+	uint32_t remaining_in_word = 64 - c->bit_index;
+
+	if (c->entries_remaining < count)
+		return -ENODATA;
+
+	if (count < remaining_in_word) {
+		c->bit_index += count;
+		c->entries_remaining -= count;
+		return 0;
+
+	} else {
+		c->entries_remaining -= remaining_in_word;
+		count -= remaining_in_word;
+	}
+
+	nr_array_skip = (count / 64) + 1;
+	r = dm_array_cursor_skip(&c->cursor, nr_array_skip);
+	if (r)
+		return r;
+
+	dm_array_cursor_get_value(&c->cursor, (void **) &value);
+	c->entries_remaining -= count;
+	c->array_index += nr_array_skip;
+	c->bit_index = count & 63;
+	c->current_bits = le64_to_cpu(*value);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dm_bitset_cursor_skip);
+
 bool dm_bitset_cursor_get_value(struct dm_bitset_cursor *c)
 {
 	return test_bit(c->bit_index, (unsigned long *) &c->current_bits);
diff --git a/drivers/md/persistent-data/dm-bitset.h b/drivers/md/persistent-data/dm-bitset.h
index a08636898a43..df888da04ee1 100644
--- a/drivers/md/persistent-data/dm-bitset.h
+++ b/drivers/md/persistent-data/dm-bitset.h
@@ -197,6 +197,7 @@ int dm_bitset_cursor_begin(struct dm_disk_bitset *info,
 void dm_bitset_cursor_end(struct dm_bitset_cursor *c);
 
 int dm_bitset_cursor_next(struct dm_bitset_cursor *c);
+int dm_bitset_cursor_skip(struct dm_bitset_cursor *c, uint32_t count);
 bool dm_bitset_cursor_get_value(struct dm_bitset_cursor *c);
 
 /*----------------------------------------------------------------*/
diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index 1744f3618a55..02e2ee0d8a00 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -1144,6 +1144,17 @@ int dm_btree_cursor_next(struct dm_btree_cursor *c)
 }
 EXPORT_SYMBOL_GPL(dm_btree_cursor_next);
 
+int dm_btree_cursor_skip(struct dm_btree_cursor *c, uint32_t count)
+{
+	int r = 0;
+
+	while (count-- && !r)
+		r = dm_btree_cursor_next(c);
+
+	return r;
+}
+EXPORT_SYMBOL_GPL(dm_btree_cursor_skip);
+
 int dm_btree_cursor_get_value(struct dm_btree_cursor *c, uint64_t *key, void *value_le)
 {
 	if (c->depth) {
diff --git a/drivers/md/persistent-data/dm-btree.h b/drivers/md/persistent-data/dm-btree.h
index db9bd26adf31..3dc5bb1a4748 100644
--- a/drivers/md/persistent-data/dm-btree.h
+++ b/drivers/md/persistent-data/dm-btree.h
@@ -209,6 +209,7 @@ int dm_btree_cursor_begin(struct dm_btree_info *info, dm_block_t root,
 			  bool prefetch_leaves, struct dm_btree_cursor *c);
 void dm_btree_cursor_end(struct dm_btree_cursor *c);
 int dm_btree_cursor_next(struct dm_btree_cursor *c);
+int dm_btree_cursor_skip(struct dm_btree_cursor *c, uint32_t count);
 int dm_btree_cursor_get_value(struct dm_btree_cursor *c, uint64_t *key, void *value_le);
 
 #endif	/* _LINUX_DM_BTREE_H */