--- zzzz-none-000/linux-3.10.107/drivers/md/persistent-data/dm-space-map-metadata.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/drivers/md/persistent-data/dm-space-map-metadata.c	2021-02-04 17:41:59.000000000 +0000
@@ -91,6 +91,77 @@
 	dm_block_t block;
 };
 
+struct bop_ring_buffer {
+	unsigned begin;
+	unsigned end;
+	struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
+};
+
+static void brb_init(struct bop_ring_buffer *brb)
+{
+	brb->begin = 0;
+	brb->end = 0;
+}
+
+static bool brb_empty(struct bop_ring_buffer *brb)
+{
+	return brb->begin == brb->end;
+}
+
+static unsigned brb_next(struct bop_ring_buffer *brb, unsigned old)
+{
+	unsigned r = old + 1;
+	return (r >= (sizeof(brb->bops) / sizeof(*brb->bops))) ? 0 : r;
+}
+
+static int brb_push(struct bop_ring_buffer *brb,
+		    enum block_op_type type, dm_block_t b)
+{
+	struct block_op *bop;
+	unsigned next = brb_next(brb, brb->end);
+
+	/*
+	 * We don't allow the last bop to be filled, this way we can
+	 * differentiate between full and empty.
+	 */
+	if (next == brb->begin)
+		return -ENOMEM;
+
+	bop = brb->bops + brb->end;
+	bop->type = type;
+	bop->block = b;
+
+	brb->end = next;
+
+	return 0;
+}
+
+static int brb_peek(struct bop_ring_buffer *brb, struct block_op *result)
+{
+	struct block_op *bop;
+
+	if (brb_empty(brb))
+		return -ENODATA;
+
+	bop = brb->bops + brb->begin;
+	result->type = bop->type;
+	result->block = bop->block;
+
+	return 0;
+}
+
+static int brb_pop(struct bop_ring_buffer *brb)
+{
+	if (brb_empty(brb))
+		return -ENODATA;
+
+	brb->begin = brb_next(brb, brb->begin);
+
+	return 0;
+}
+
+/*----------------------------------------------------------------*/
+
 struct sm_metadata {
 	struct dm_space_map sm;
 
@@ -101,25 +172,20 @@
 
 	unsigned recursion_count;
 	unsigned allocated_this_transaction;
-	unsigned nr_uncommitted;
-	struct block_op uncommitted[MAX_RECURSIVE_ALLOCATIONS];
+	struct bop_ring_buffer uncommitted;
 
 	struct threshold threshold;
 };
 
 static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
 {
-	struct block_op *op;
+	int r = brb_push(&smm->uncommitted, type, b);
 
-	if (smm->nr_uncommitted == MAX_RECURSIVE_ALLOCATIONS) {
+	if (r) {
 		DMERR("too many recursive allocations");
 		return -ENOMEM;
 	}
 
-	op = smm->uncommitted + smm->nr_uncommitted++;
-	op->type = type;
-	op->block = b;
-
 	return 0;
 }
 
@@ -146,6 +212,29 @@
 	smm->recursion_count++;
 }
 
+static int apply_bops(struct sm_metadata *smm)
+{
+	int r = 0;
+
+	while (!brb_empty(&smm->uncommitted)) {
+		struct block_op bop;
+
+		r = brb_peek(&smm->uncommitted, &bop);
+		if (r) {
+			DMERR("bug in bop ring buffer");
+			break;
+		}
+
+		r = commit_bop(smm, &bop);
+		if (r)
+			break;
+
+		brb_pop(&smm->uncommitted);
+	}
+
+	return r;
+}
+
 static int out(struct sm_metadata *smm)
 {
 	int r = 0;
@@ -158,15 +247,8 @@
 		return -ENOMEM;
 	}
 
-	if (smm->recursion_count == 1 && smm->nr_uncommitted) {
-		while (smm->nr_uncommitted && !r) {
-			smm->nr_uncommitted--;
-			r = commit_bop(smm, smm->uncommitted +
-				       smm->nr_uncommitted);
-			if (r)
-				break;
-		}
-	}
+	if (smm->recursion_count == 1)
+		apply_bops(smm);
 
 	smm->recursion_count--;
 
@@ -217,7 +299,8 @@
 static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
 				 uint32_t *result)
 {
-	int r, i;
+	int r;
+	unsigned i;
 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 	unsigned adjustment = 0;
 
@@ -225,8 +308,10 @@
 	 * We may have some uncommitted adjustments to add.  This list
 	 * should always be really short.
 	 */
-	for (i = 0; i < smm->nr_uncommitted; i++) {
-		struct block_op *op = smm->uncommitted + i;
+	for (i = smm->uncommitted.begin;
+	     i != smm->uncommitted.end;
+	     i = brb_next(&smm->uncommitted, i)) {
+		struct block_op *op = smm->uncommitted.bops + i;
 
 		if (op->block != b)
 			continue;
@@ -254,7 +339,8 @@
 static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
 					      dm_block_t b, int *result)
 {
-	int r, i, adjustment = 0;
+	int r, adjustment = 0;
+	unsigned i;
 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 	uint32_t rc;
 
@@ -262,8 +348,11 @@
 	 * We may have some uncommitted adjustments to add.  This list
 	 * should always be really short.
 	 */
-	for (i = 0; i < smm->nr_uncommitted; i++) {
-		struct block_op *op = smm->uncommitted + i;
+	for (i = smm->uncommitted.begin;
+	     i != smm->uncommitted.end;
+	     i = brb_next(&smm->uncommitted, i)) {
+
+		struct block_op *op = smm->uncommitted.bops + i;
 
 		if (op->block != b)
 			continue;
@@ -385,13 +474,13 @@
 
 	int r = sm_metadata_new_block_(sm, b);
 	if (r) {
-		DMERR("unable to allocate new metadata block");
+		DMERR_LIMIT("unable to allocate new metadata block");
 		return r;
 	}
 
 	r = sm_metadata_get_nr_free(sm, &count);
 	if (r) {
-		DMERR("couldn't get free block count");
+		DMERR_LIMIT("couldn't get free block count");
 		return r;
 	}
 
@@ -512,7 +601,9 @@
 {
 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 
-	return b < smm->begin ? 1 : 0;
+	*result = (b < smm->begin) ? 1 : 0;
+
+	return 0;
 }
 
 static int sm_bootstrap_count_is_more_than_one(struct dm_space_map *sm,
@@ -602,7 +693,6 @@
 static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
 {
 	int r, i;
-	enum allocation_event ev;
 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 	dm_block_t old_len = smm->ll.nr_blocks;
 
@@ -624,13 +714,20 @@
 	 * allocate any new blocks.
 	 */
 	do {
-		for (i = old_len; !r && i < smm->begin; i++) {
-			r = sm_ll_inc(&smm->ll, i, &ev);
-			if (r)
-				goto out;
-		}
+		for (i = old_len; !r && i < smm->begin; i++)
+			r = add_bop(smm, BOP_INC, i);
+
+		if (r)
+			goto out;
+
 		old_len = smm->begin;
 
+		r = apply_bops(smm);
+		if (r) {
+			DMERR("%s: apply_bops failed", __func__);
+			goto out;
+		}
+
 		r = sm_ll_commit(&smm->ll);
 		if (r)
 			goto out;
@@ -667,19 +764,20 @@
 {
 	int r;
 	dm_block_t i;
-	enum allocation_event ev;
 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 
 	smm->begin = superblock + 1;
 	smm->recursion_count = 0;
 	smm->allocated_this_transaction = 0;
-	smm->nr_uncommitted = 0;
+	brb_init(&smm->uncommitted);
 	threshold_init(&smm->threshold);
 
 	memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));
 
 	r = sm_ll_new_metadata(&smm->ll, tm);
 	if (!r) {
+		if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
+			nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
 		r = sm_ll_extend(&smm->ll, nr_blocks);
 	}
 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
@@ -691,11 +789,17 @@
 	 * allocated blocks that they were built from.
 	 */
 	for (i = superblock; !r && i < smm->begin; i++)
-		r = sm_ll_inc(&smm->ll, i, &ev);
+		r = add_bop(smm, BOP_INC, i);
 
 	if (r)
 		return r;
 
+	r = apply_bops(smm);
+	if (r) {
+		DMERR("%s: apply_bops failed", __func__);
+		return r;
+	}
+
 	return sm_metadata_commit(sm);
 }
 
@@ -713,7 +817,7 @@
 	smm->begin = 0;
 	smm->recursion_count = 0;
 	smm->allocated_this_transaction = 0;
-	smm->nr_uncommitted = 0;
+	brb_init(&smm->uncommitted);
 	threshold_init(&smm->threshold);
 
 	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));