[v4,6/8] lightnvm: RRPC target
diff mbox

Message ID 1433508870-28251-7-git-send-email-m@bjorling.me
State New
Headers show

Commit Message

Matias Bjorling June 5, 2015, 12:54 p.m. UTC
This target implements a simple strategy FTL for Open-Channel SSDs.
It does round-robin selection across channels and lunis. It uses a
simple greedy cost-based garbage collector and exposes the physical
flash as a block device.

Signed-off-by: Javier González <jg@lightnvm.io>
Signed-off-by: Matias Bjørling <m@bjorling.me>
---
 drivers/lightnvm/Kconfig  |   10 +
 drivers/lightnvm/Makefile |    1 +
 drivers/lightnvm/rrpc.c   | 1088 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/lightnvm/rrpc.h   |  221 +++++++++
 include/linux/blkdev.h    |    2 +
 5 files changed, 1322 insertions(+)
 create mode 100644 drivers/lightnvm/rrpc.c
 create mode 100644 drivers/lightnvm/rrpc.h

Patch
diff mbox

diff --git a/drivers/lightnvm/Kconfig b/drivers/lightnvm/Kconfig
index 1f8412c..1773891 100644
--- a/drivers/lightnvm/Kconfig
+++ b/drivers/lightnvm/Kconfig
@@ -14,3 +14,13 @@  menuconfig NVM
 	  If you say N, all options in this submenu will be skipped and disabled
 	  only do this if you know what you are doing.
 
+if NVM
+
+config NVM_RRPC
+	tristate "Round-robin Hybrid Open-Channel SSD"
+	---help---
+	Allows an open-channel SSD to be exposed as a block device to the
+	host. The target is implemented using a linear mapping table and
+	cost-based garbage collection. It is optimized for 4K IO sizes.
+
+endif # NVM
diff --git a/drivers/lightnvm/Makefile b/drivers/lightnvm/Makefile
index 38185e9..b2a39e2 100644
--- a/drivers/lightnvm/Makefile
+++ b/drivers/lightnvm/Makefile
@@ -3,3 +3,4 @@ 
 #
 
 obj-$(CONFIG_NVM)		:= core.o
+obj-$(CONFIG_NVM_RRPC)		+= rrpc.o
diff --git a/drivers/lightnvm/rrpc.c b/drivers/lightnvm/rrpc.c
new file mode 100644
index 0000000..d3a7f16
--- /dev/null
+++ b/drivers/lightnvm/rrpc.c
@@ -0,0 +1,1088 @@ 
+/*
+ * Copyright (C) 2015 IT University of Copenhagen
+ * Initial release: Matias Bjorling <mabj@itu.dk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * Implementation of a Round-robin page-based Hybrid FTL for Open-channel SSDs.
+ */
+
+#include "rrpc.h"
+
+static struct kmem_cache *_gcb_cache;
+static DECLARE_RWSEM(_lock);
+
+#define rrpc_for_each_lun(rrpc, rlun, i) \
+		for ((i) = 0, rlun = &(rrpc)->luns[0]; \
+			(i) < (rrpc)->nr_luns; (i)++, rlun = &(rrpc)->luns[(i)])
+
+static void invalidate_block_page(struct nvm_addr *p)
+{
+	struct nvm_block *block = p->block;
+	unsigned int page_offset;
+
+	if (!block)
+		return;
+
+	spin_lock(&block->lock);
+	page_offset = p->addr % block->lun->nr_pages_per_blk;
+	WARN_ON(test_and_set_bit(page_offset, block->invalid_pages));
+	block->nr_invalid_pages++;
+	spin_unlock(&block->lock);
+}
+
+static inline void __nvm_page_invalidate(struct rrpc *rrpc, struct nvm_addr *a)
+{
+	BUG_ON(!spin_is_locked(&rrpc->rev_lock));
+	if (a->addr == ADDR_EMPTY)
+		return;
+
+	invalidate_block_page(a);
+	rrpc->rev_trans_map[a->addr - rrpc->poffset].addr = ADDR_EMPTY;
+}
+
+static void rrpc_invalidate_range(struct rrpc *rrpc, sector_t slba,
+								unsigned len)
+{
+	sector_t i;
+
+	spin_lock(&rrpc->rev_lock);
+	for (i = slba; i < slba + len; i++) {
+		struct nvm_addr *gp = &rrpc->trans_map[i];
+
+		__nvm_page_invalidate(rrpc, gp);
+		gp->block = NULL;
+	}
+	spin_unlock(&rrpc->rev_lock);
+}
+
+static struct request *rrpc_inflight_laddr_acquire(struct rrpc *rrpc,
+					sector_t laddr, unsigned int pages)
+{
+	struct request *rq;
+	struct rrpc_inflight_rq *inf;
+
+	rq = blk_mq_alloc_request(rrpc->q_dev, READ, GFP_NOIO, false);
+	if (!rq)
+		return ERR_PTR(-ENOMEM);
+
+	inf = rrpc_get_inflight_rq(rq);
+	if (rrpc_lock_laddr(rrpc, laddr, pages, inf)) {
+		blk_mq_free_request(rq);
+		return NULL;
+	}
+
+	return rq;
+}
+
+static void rrpc_inflight_laddr_release(struct rrpc *rrpc, struct request *rq)
+{
+	struct rrpc_inflight_rq *inf;
+
+	inf = rrpc_get_inflight_rq(rq);
+	rrpc_unlock_laddr(rrpc, inf->l_start, inf);
+
+	blk_mq_free_request(rq);
+}
+
+static void rrpc_discard(struct rrpc *rrpc, struct bio *bio)
+{
+	sector_t slba = bio->bi_iter.bi_sector / NR_PHY_IN_LOG;
+	sector_t len = bio->bi_iter.bi_size / EXPOSED_PAGE_SIZE;
+	struct request *rq;
+
+	do {
+		rq = rrpc_inflight_laddr_acquire(rrpc, slba, len);
+		schedule();
+	} while (!rq);
+
+	if (IS_ERR(rq)) {
+		bio_io_error(bio);
+		return;
+	}
+
+	rrpc_invalidate_range(rrpc, slba, len);
+	rrpc_inflight_laddr_release(rrpc, rq);
+}
+
+/* requires lun->lock taken */
+static void rrpc_set_lun_cur(struct rrpc_lun *rlun, struct nvm_block *block)
+{
+	BUG_ON(!block);
+
+	if (rlun->cur) {
+		spin_lock(&rlun->cur->lock);
+		WARN_ON(!block_is_full(rlun->cur));
+		spin_unlock(&rlun->cur->lock);
+	}
+	rlun->cur = block;
+}
+
+static struct rrpc_lun *get_next_lun(struct rrpc *rrpc)
+{
+	int next = atomic_inc_return(&rrpc->next_lun);
+
+	return &rrpc->luns[next % rrpc->nr_luns];
+}
+
+static void rrpc_gc_kick(struct rrpc *rrpc)
+{
+	struct rrpc_lun *rlun;
+	unsigned int i;
+
+	for (i = 0; i < rrpc->nr_luns; i++) {
+		rlun = &rrpc->luns[i];
+		queue_work(rrpc->krqd_wq, &rlun->ws_gc);
+	}
+}
+
+/**
+ * rrpc_gc_timer - default gc timer function.
+ * @data: ptr to the 'nvm' structure
+ *
+ * Description:
+ *   rrpc configures a timer to kick the GC to force proactive behavior.
+ *
+ **/
+static void rrpc_gc_timer(unsigned long data)
+{
+	struct rrpc *rrpc = (struct rrpc *)data;
+
+	rrpc_gc_kick(rrpc);
+	mod_timer(&rrpc->gc_timer, jiffies + msecs_to_jiffies(10));
+}
+
+/*
+ * rrpc_move_valid_pages -- migrate live data off the block
+ * @rrpc: the 'rrpc' structure
+ * @block: the block from which to migrate live pages
+ *
+ * Description:
+ *   GC algorithms may call this function to migrate remaining live
+ *   pages off the block prior to erasing it. This function blocks
+ *   further execution until the operation is complete.
+ */
+static int rrpc_move_valid_pages(struct rrpc *rrpc, struct nvm_block *block)
+{
+	struct nvm_dev *dev = rrpc->q_nvm;
+	struct nvm_lun *lun = block->lun;
+	struct nvm_internal_cmd cmd = {
+		.target = &rrpc->instance,
+		.timeout = 30,
+	};
+	struct nvm_rev_addr *rev;
+	struct request *rq;
+	struct page *page;
+	int slot;
+	int ret;
+	sector_t phys_addr;
+
+	if (bitmap_full(block->invalid_pages, lun->nr_pages_per_blk))
+		return 0;
+
+	page = mempool_alloc(rrpc->page_pool, GFP_NOIO);
+
+	while ((slot = find_first_zero_bit(block->invalid_pages,
+					   lun->nr_pages_per_blk)) <
+						lun->nr_pages_per_blk) {
+
+		/* Lock laddr */
+		phys_addr = block_to_addr(block) + slot;
+
+try:
+		spin_lock(&rrpc->rev_lock);
+		/* Get logical address from physical to logical table */
+		rev = &rrpc->rev_trans_map[phys_addr - rrpc->poffset];
+		/* already updated by previous regular write */
+		if (rev->addr == ADDR_EMPTY) {
+			spin_unlock(&rrpc->rev_lock);
+			continue;
+		}
+
+		rq = rrpc_inflight_laddr_acquire(rrpc, rev->addr, 1);
+		if (!rq) {
+			spin_unlock(&rrpc->rev_lock);
+			schedule();
+			goto try;
+		}
+
+		spin_unlock(&rrpc->rev_lock);
+
+		cmd.phys_lba = rev->addr;
+		cmd.rw = READ;
+		cmd.buffer = page_address(page);
+		cmd.bufflen = EXPOSED_PAGE_SIZE;
+		ret = nvm_internal_rw(dev, &cmd);
+		if (ret) {
+			pr_err("nvm: gc read failure.\n");
+			goto out;
+		}
+
+		/* turn the command around and write the data back to a new
+		 * address */
+		cmd.rw = WRITE;
+		ret = nvm_internal_rw(dev, &cmd);
+		if (ret) {
+			pr_err("nvm: gc write failure.\n");
+			goto out;
+		}
+
+		rrpc_inflight_laddr_release(rrpc, rq);
+	}
+
+	mempool_free(page, rrpc->page_pool);
+
+out:
+	if (!bitmap_full(block->invalid_pages, lun->nr_pages_per_blk)) {
+		pr_err("nvm: failed to garbage collect block\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static void rrpc_block_gc(struct work_struct *work)
+{
+	struct rrpc_block_gc *gcb = container_of(work, struct rrpc_block_gc,
+									ws_gc);
+	struct rrpc *rrpc = gcb->rrpc;
+	struct nvm_block *block = gcb->block;
+	struct nvm_dev *dev = rrpc->q_nvm;
+
+	pr_debug("nvm: block '%d' being reclaimed\n", block->id);
+
+	if (rrpc_move_valid_pages(rrpc, block))
+		goto done;
+
+	nvm_erase_blk(dev, block);
+	nvm_put_blk(block);
+done:
+	mempool_free(gcb, rrpc->gcb_pool);
+}
+
+/* the block with highest number of invalid pages, will be in the beginning
+ * of the list */
+static struct rrpc_block *rblock_max_invalid(struct rrpc_block *ra,
+					       struct rrpc_block *rb)
+{
+	struct nvm_block *a = ra->parent;
+	struct nvm_block *b = rb->parent;
+
+	BUG_ON(!a || !b);
+
+	if (a->nr_invalid_pages == b->nr_invalid_pages)
+		return ra;
+
+	return (a->nr_invalid_pages < b->nr_invalid_pages) ? rb : ra;
+}
+
+/* linearly find the block with highest number of invalid pages
+ * requires lun->lock */
+static struct rrpc_block *block_prio_find_max(struct rrpc_lun *rlun)
+{
+	struct list_head *prio_list = &rlun->prio_list;
+	struct rrpc_block *rblock, *max;
+
+	BUG_ON(list_empty(prio_list));
+
+	max = list_first_entry(prio_list, struct rrpc_block, prio);
+	list_for_each_entry(rblock, prio_list, prio)
+		max = rblock_max_invalid(max, rblock);
+
+	return max;
+}
+
+static void rrpc_lun_gc(struct work_struct *work)
+{
+	struct rrpc_lun *rlun = container_of(work, struct rrpc_lun, ws_gc);
+	struct rrpc *rrpc = rlun->rrpc;
+	struct nvm_lun *lun = rlun->parent;
+	struct rrpc_block_gc *gcb;
+	unsigned int nr_blocks_need;
+
+	nr_blocks_need = lun->nr_blocks / GC_LIMIT_INVERSE;
+
+	if (nr_blocks_need < rrpc->nr_luns)
+		nr_blocks_need = rrpc->nr_luns;
+
+	spin_lock(&lun->lock);
+	while (nr_blocks_need > lun->nr_free_blocks &&
+					!list_empty(&rlun->prio_list)) {
+		struct rrpc_block *rblock = block_prio_find_max(rlun);
+		struct nvm_block *block = rblock->parent;
+
+		if (!block->nr_invalid_pages)
+			break;
+
+		list_del_init(&rblock->prio);
+
+		BUG_ON(!block_is_full(block));
+
+		pr_debug("nvm: selected block '%d' as GC victim\n",
+								block->id);
+
+		gcb = mempool_alloc(rrpc->gcb_pool, GFP_ATOMIC);
+		if (!gcb)
+			break;
+
+		gcb->rrpc = rrpc;
+		gcb->block = rblock->parent;
+		INIT_WORK(&gcb->ws_gc, rrpc_block_gc);
+
+		queue_work(rrpc->kgc_wq, &gcb->ws_gc);
+
+		nr_blocks_need--;
+	}
+	spin_unlock(&lun->lock);
+
+	/* TODO: Hint that request queue can be started again */
+}
+
+static void rrpc_gc_queue(struct work_struct *work)
+{
+	struct rrpc_block_gc *gcb = container_of(work, struct rrpc_block_gc,
+									ws_gc);
+	struct rrpc *rrpc = gcb->rrpc;
+	struct nvm_block *block = gcb->block;
+	struct nvm_lun *lun = block->lun;
+	struct rrpc_lun *rlun = &rrpc->luns[lun->id - rrpc->lun_offset];
+	struct rrpc_block *rblock =
+			&rlun->blocks[block->id % lun->nr_blocks];
+
+	spin_lock(&rlun->lock);
+	list_add_tail(&rblock->prio, &rlun->prio_list);
+	spin_unlock(&rlun->lock);
+
+	mempool_free(gcb, rrpc->gcb_pool);
+	pr_debug("nvm: block '%d' is full, allow GC (sched)\n", block->id);
+}
+
+static int rrpc_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd,
+							unsigned long arg)
+{
+	return 0;
+}
+
+static int rrpc_open(struct block_device *bdev, fmode_t mode)
+{
+	return 0;
+}
+
+static void rrpc_release(struct gendisk *disk, fmode_t mode)
+{
+}
+
+static const struct block_device_operations rrpc_fops = {
+	.owner		= THIS_MODULE,
+	.ioctl		= rrpc_ioctl,
+	.open		= rrpc_open,
+	.release	= rrpc_release,
+};
+
+static struct rrpc_lun *__rrpc_get_lun_rr(struct rrpc *rrpc, int is_gc)
+{
+	unsigned int i;
+	struct rrpc_lun *rlun, *max_free;
+
+	if (!is_gc)
+		return get_next_lun(rrpc);
+
+	/* FIXME */
+	/* during GC, we don't care about RR, instead we want to make
+	 * sure that we maintain evenness between the block luns. */
+	max_free = &rrpc->luns[0];
+	/* prevent GC-ing lun from devouring pages of a lun with
+	 * little free blocks. We don't take the lock as we only need an
+	 * estimate. */
+	rrpc_for_each_lun(rrpc, rlun, i) {
+		if (rlun->parent->nr_free_blocks >
+					max_free->parent->nr_free_blocks)
+			max_free = rlun;
+	}
+
+	return max_free;
+}
+
+static inline void __rrpc_page_invalidate(struct rrpc *rrpc,
+							struct nvm_addr *gp)
+{
+	BUG_ON(!spin_is_locked(&rrpc->rev_lock));
+	if (gp->addr == ADDR_EMPTY)
+		return;
+
+	invalidate_block_page(gp);
+	rrpc->rev_trans_map[gp->addr - rrpc->poffset].addr = ADDR_EMPTY;
+}
+
+struct nvm_addr *nvm_update_map(struct rrpc *rrpc, sector_t l_addr,
+			struct nvm_block *p_block, sector_t p_addr, int is_gc)
+{
+	struct nvm_addr *gp;
+	struct nvm_rev_addr *rev;
+
+	BUG_ON(l_addr >= rrpc->nr_pages);
+
+	gp = &rrpc->trans_map[l_addr];
+	spin_lock(&rrpc->rev_lock);
+	if (gp->block)
+		__nvm_page_invalidate(rrpc, gp);
+
+	gp->addr = p_addr;
+	gp->block = p_block;
+
+	rev = &rrpc->rev_trans_map[gp->addr - rrpc->poffset];
+	rev->addr = l_addr;
+	spin_unlock(&rrpc->rev_lock);
+
+	return gp;
+}
+
+/* Simple round-robin Logical to physical address translation.
+ *
+ * Retrieve the mapping using the active append point. Then update the ap for
+ * the next write to the disk.
+ *
+ * Returns nvm_addr with the physical address and block. Remember to return to
+ * rrpc->addr_cache when request is finished.
+ */
+static struct nvm_addr *rrpc_map_page(struct rrpc *rrpc, sector_t laddr,
+								int is_gc)
+{
+	struct rrpc_lun *rlun;
+	struct nvm_lun *lun;
+	struct nvm_block *p_block;
+	sector_t p_addr;
+
+	rlun = __rrpc_get_lun_rr(rrpc, is_gc);
+	lun = rlun->parent;
+
+	if (!is_gc && lun->nr_free_blocks < rrpc->nr_luns * 4)
+		return NULL;
+
+	spin_lock(&rlun->lock);
+
+	p_block = rlun->cur;
+	p_addr = nvm_alloc_addr(p_block);
+
+	if (p_addr == ADDR_EMPTY) {
+		p_block = nvm_get_blk(lun, 0);
+
+		if (!p_block) {
+			if (is_gc) {
+				p_addr = nvm_alloc_addr(rlun->gc_cur);
+				if (p_addr == ADDR_EMPTY) {
+					p_block = nvm_get_blk(lun, 1);
+					if (!p_block) {
+						pr_err("rrpc: no more blocks");
+						goto finished;
+					} else {
+						rlun->gc_cur = p_block;
+						p_addr =
+						  nvm_alloc_addr(rlun->gc_cur);
+					}
+				}
+				p_block = rlun->gc_cur;
+			}
+			goto finished;
+		}
+
+		rrpc_set_lun_cur(rlun, p_block);
+		p_addr = nvm_alloc_addr(p_block);
+	}
+
+finished:
+	if (p_addr == ADDR_EMPTY)
+		goto err;
+
+	if (!p_block)
+		WARN_ON(is_gc);
+
+	spin_unlock(&rlun->lock);
+	return nvm_update_map(rrpc, laddr, p_block, p_addr, is_gc);
+err:
+	spin_unlock(&rlun->lock);
+	return NULL;
+}
+
+static void rrpc_unprep_rq(struct request *rq, struct nvm_rq_data *rqdata,
+								void *private)
+{
+	struct rrpc *rrpc = private;
+	struct nvm_per_rq *pb = get_per_rq_data(rq);
+	struct nvm_addr *p = pb->addr;
+	struct nvm_block *block = p->block;
+	struct nvm_lun *lun = block->lun;
+	struct rrpc_block_gc *gcb;
+	int cmnt_size;
+
+	rrpc_unlock_rq(rrpc, rq);
+
+	if (rq_data_dir(rq) == WRITE) {
+		cmnt_size = atomic_inc_return(&block->data_cmnt_size);
+		if (likely(cmnt_size != lun->nr_pages_per_blk))
+			return;
+
+		gcb = mempool_alloc(rrpc->gcb_pool, GFP_ATOMIC);
+		if (!gcb) {
+			pr_err("rrpc: not able to queue block for gc.");
+			return;
+		}
+
+		gcb->rrpc = rrpc;
+		gcb->block = block;
+		INIT_WORK(&gcb->ws_gc, rrpc_gc_queue);
+
+		queue_work(rrpc->kgc_wq, &gcb->ws_gc);
+	}
+}
+
+static int rrpc_read_rq(struct rrpc *rrpc, struct request *rq,
+						struct nvm_rq_data *rqdata)
+{
+	struct nvm_addr *gp;
+	struct nvm_per_rq *pb;
+	sector_t l_addr = nvm_get_laddr(rq);
+
+	if (rrpc_lock_rq(rrpc, rq))
+		return NVM_PREP_REQUEUE;
+
+	BUG_ON(!(l_addr >= 0 && l_addr < rrpc->nr_pages));
+	gp = &rrpc->trans_map[l_addr];
+
+	if (gp->block) {
+		rqdata->phys_sector = nvm_get_sector(gp->addr);
+	} else {
+		rrpc_unlock_rq(rrpc, rq);
+		blk_mq_end_request(rq, 0);
+		return NVM_PREP_DONE;
+	}
+
+	pb = get_per_rq_data(rq);
+	pb->addr = gp;
+	return NVM_PREP_OK;
+}
+
+static int rrpc_write_rq(struct rrpc *rrpc, struct request *rq,
+						struct nvm_rq_data *rqdata)
+{
+	struct nvm_per_rq *pb;
+	struct nvm_addr *p;
+	int is_gc = 0;
+	sector_t l_addr = nvm_get_laddr(rq);
+
+	if (rq->special)
+		is_gc = 1;
+
+	if (rrpc_lock_rq(rrpc, rq))
+		return NVM_PREP_REQUEUE;
+
+	p = rrpc_map_page(rrpc, l_addr, is_gc);
+	if (!p) {
+		BUG_ON(is_gc);
+		rrpc_unlock_rq(rrpc, rq);
+		rrpc_gc_kick(rrpc);
+		return NVM_PREP_REQUEUE;
+	}
+
+	rqdata->phys_sector = nvm_get_sector(p->addr);
+
+	pb = get_per_rq_data(rq);
+	pb->addr = p;
+
+	return NVM_PREP_OK;
+}
+
+static int rrpc_prep_rq(struct request *rq, struct nvm_rq_data *rqdata,
+								void *private)
+{
+	struct rrpc *rrpc = private;
+
+	if (rq_data_dir(rq) == WRITE)
+		return rrpc_write_rq(rrpc, rq, rqdata);
+
+	return rrpc_read_rq(rrpc, rq, rqdata);
+}
+
+static void rrpc_make_rq(struct request_queue *q, struct bio *bio)
+{
+	struct rrpc *rrpc = q->queuedata;
+
+	if (bio->bi_rw & REQ_DISCARD) {
+		rrpc_discard(rrpc, bio);
+		return;
+	}
+
+	bio->bi_nvm = &rrpc->instance.payload;
+	bio->bi_bdev = rrpc->q_bdev;
+
+	generic_make_request(bio);
+}
+
+static void rrpc_gc_free(struct rrpc *rrpc)
+{
+	struct rrpc_lun *rlun;
+	int i;
+
+	if (rrpc->krqd_wq)
+		destroy_workqueue(rrpc->krqd_wq);
+
+	if (rrpc->kgc_wq)
+		destroy_workqueue(rrpc->kgc_wq);
+
+	if (!rrpc->luns)
+		return;
+
+	for (i = 0; i < rrpc->nr_luns; i++) {
+		rlun = &rrpc->luns[i];
+
+		if (!rlun->blocks)
+			break;
+		vfree(rlun->blocks);
+	}
+}
+
+static int rrpc_gc_init(struct rrpc *rrpc)
+{
+	rrpc->krqd_wq = alloc_workqueue("knvm-work", WQ_MEM_RECLAIM|WQ_UNBOUND,
+						rrpc->nr_luns);
+	if (!rrpc->krqd_wq)
+		return -ENOMEM;
+
+	rrpc->kgc_wq = alloc_workqueue("knvm-gc", WQ_MEM_RECLAIM, 1);
+	if (!rrpc->kgc_wq)
+		return -ENOMEM;
+
+	setup_timer(&rrpc->gc_timer, rrpc_gc_timer, (unsigned long)rrpc);
+
+	return 0;
+}
+
+static void rrpc_map_free(struct rrpc *rrpc)
+{
+	vfree(rrpc->rev_trans_map);
+	vfree(rrpc->trans_map);
+}
+
+static int rrpc_l2p_update(u64 slba, u64 nlb, u64 *entries, void *private)
+{
+	struct rrpc *rrpc = (struct rrpc *)private;
+	struct nvm_dev *dev = rrpc->q_nvm;
+	struct nvm_addr *addr = rrpc->trans_map + slba;
+	struct nvm_rev_addr *raddr = rrpc->rev_trans_map;
+	sector_t max_pages = dev->total_pages * (dev->sector_size >> 9);
+	u64 elba = slba + nlb;
+	u64 i;
+
+	if (unlikely(elba > dev->total_pages)) {
+		pr_err("nvm: L2P data from device is out of bounds!\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < nlb; i++) {
+		u64 pba = le64_to_cpu(entries[i]);
+		/* LNVM treats address-spaces as silos, LBA and PBA are
+		 * equally large and zero-indexed. */
+		if (unlikely(pba >= max_pages && pba != U64_MAX)) {
+			pr_err("nvm: L2P data entry is out of bounds!\n");
+			return -EINVAL;
+		}
+
+		/* Address zero is a special one. The first page on a disk is
+		 * protected. As it often holds internal device boot
+		 * information. */
+		if (!pba)
+			continue;
+
+		addr[i].addr = pba;
+		raddr[pba].addr = slba + i;
+	}
+
+	return 0;
+}
+
+static int rrpc_map_init(struct rrpc *rrpc)
+{
+	struct nvm_dev *dev = rrpc->q_nvm;
+	sector_t i;
+	int ret;
+
+	rrpc->trans_map = vzalloc(sizeof(struct nvm_addr) * rrpc->nr_pages);
+	if (!rrpc->trans_map)
+		return -ENOMEM;
+
+	rrpc->rev_trans_map = vmalloc(sizeof(struct nvm_rev_addr)
+							* rrpc->nr_pages);
+	if (!rrpc->rev_trans_map)
+		return -ENOMEM;
+
+	for (i = 0; i < rrpc->nr_pages; i++) {
+		struct nvm_addr *p = &rrpc->trans_map[i];
+		struct nvm_rev_addr *r = &rrpc->rev_trans_map[i];
+
+		p->addr = ADDR_EMPTY;
+		r->addr = ADDR_EMPTY;
+	}
+
+	if (!dev->ops->get_l2p_tbl)
+		return 0;
+
+	/* Bring up the mapping table from device */
+	ret = dev->ops->get_l2p_tbl(dev->q, 0, dev->total_pages,
+							rrpc_l2p_update, rrpc);
+	if (ret) {
+		pr_err("nvm: rrpc: could not read L2P table.\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+
+/* Minimum pages needed within a lun */
+#define PAGE_POOL_SIZE 16
+#define ADDR_POOL_SIZE 64
+
+static int rrpc_core_init(struct rrpc *rrpc)
+{
+	int i;
+
+	down_write(&_lock);
+	if (!_gcb_cache) {
+		_gcb_cache = kmem_cache_create("nvm_gcb_cache",
+				sizeof(struct rrpc_block_gc), 0, 0, NULL);
+		if (!_gcb_cache) {
+			up_write(&_lock);
+			return -ENOMEM;
+		}
+	}
+	up_write(&_lock);
+
+	rrpc->page_pool = mempool_create_page_pool(PAGE_POOL_SIZE, 0);
+	if (!rrpc->page_pool)
+		return -ENOMEM;
+
+	rrpc->gcb_pool = mempool_create_slab_pool(rrpc->q_nvm->nr_luns,
+								_gcb_cache);
+	if (!rrpc->gcb_pool)
+		return -ENOMEM;
+
+	for (i = 0; i < NVM_INFLIGHT_PARTITIONS; i++) {
+		struct nvm_inflight *map = &rrpc->inflight_map[i];
+
+		spin_lock_init(&map->lock);
+		INIT_LIST_HEAD(&map->reqs);
+	}
+
+	return 0;
+}
+
+static void rrpc_core_free(struct rrpc *rrpc)
+{
+	if (rrpc->page_pool)
+		mempool_destroy(rrpc->page_pool);
+	if (rrpc->gcb_pool)
+		mempool_destroy(rrpc->gcb_pool);
+}
+
+static void rrpc_luns_free(struct rrpc *rrpc)
+{
+	kfree(rrpc->luns);
+}
+
+static int rrpc_luns_init(struct rrpc *rrpc, int lun_begin, int lun_end)
+{
+	struct nvm_dev *dev = rrpc->q_nvm;
+	struct nvm_block *block;
+	struct rrpc_lun *rlun;
+	int i, j;
+
+	spin_lock_init(&rrpc->rev_lock);
+
+	rrpc->luns = kcalloc(rrpc->nr_luns, sizeof(struct rrpc_lun),
+								GFP_KERNEL);
+	if (!rrpc->luns)
+		return -ENOMEM;
+
+	/* 1:1 mapping */
+	for (i = 0; i < rrpc->nr_luns; i++) {
+		struct nvm_lun *lun = &dev->luns[i + lun_begin];
+
+		rlun = &rrpc->luns[i];
+		rlun->rrpc = rrpc;
+		rlun->parent = lun;
+		rlun->nr_blocks = lun->nr_blocks;
+
+		rrpc->total_blocks += lun->nr_blocks;
+		rrpc->nr_pages += lun->nr_blocks * lun->nr_pages_per_blk;
+
+		INIT_LIST_HEAD(&rlun->prio_list);
+		INIT_WORK(&rlun->ws_gc, rrpc_lun_gc);
+		spin_lock_init(&rlun->lock);
+
+		rlun->blocks = vzalloc(sizeof(struct rrpc_block) *
+						 rlun->nr_blocks);
+		if (!rlun->blocks)
+			goto err;
+
+		lun_for_each_block(lun, block, j) {
+			struct rrpc_block *rblock = &rlun->blocks[j];
+
+			rblock->parent = block;
+			INIT_LIST_HEAD(&rblock->prio);
+		}
+	}
+
+	return 0;
+err:
+	return -ENOMEM;
+}
+
+static void rrpc_free(struct rrpc *rrpc)
+{
+	rrpc_gc_free(rrpc);
+	rrpc_map_free(rrpc);
+	rrpc_core_free(rrpc);
+	rrpc_luns_free(rrpc);
+
+	kfree(rrpc);
+}
+
+static void rrpc_exit(void *private)
+{
+	struct rrpc *rrpc = private;
+
+	blkdev_put(rrpc->q_bdev, FMODE_WRITE | FMODE_READ);
+	del_timer(&rrpc->gc_timer);
+
+	flush_workqueue(rrpc->krqd_wq);
+	flush_workqueue(rrpc->kgc_wq);
+
+	rrpc_free(rrpc);
+}
+
+static sector_t rrpc_capacity(void *private)
+{
+	struct rrpc *rrpc = private;
+	struct nvm_lun *lun;
+	sector_t reserved;
+	int i, max_pages_per_blk = 0;
+
+	nvm_for_each_lun(rrpc->q_nvm, lun, i) {
+		if (lun->nr_pages_per_blk > max_pages_per_blk)
+			max_pages_per_blk = lun->nr_pages_per_blk;
+	}
+
+	/* cur, gc, and two emergency blocks for each lun */
+	reserved = rrpc->nr_luns * max_pages_per_blk * 4;
+
+	if (reserved > rrpc->nr_pages) {
+		pr_err("rrpc: not enough space available to expose storage.\n");
+		return 0;
+	}
+
+	return ((rrpc->nr_pages - reserved) / 10) * 9 * NR_PHY_IN_LOG;
+}
+
+/*
+ * Looks up the logical address from reverse trans map and check if its valid by
+ * comparing the logical to physical address with the physical address.
+ * Returns 0 on free, otherwise 1 if in use
+ */
+static void rrpc_block_map_update(struct rrpc *rrpc, struct nvm_block *block)
+{
+	struct nvm_lun *lun = block->lun;
+	int offset;
+	struct nvm_addr *laddr;
+	sector_t paddr, pladdr;
+
+	for (offset = 0; offset < lun->nr_pages_per_blk; offset++) {
+		paddr = block_to_addr(block) + offset;
+
+		pladdr = rrpc->rev_trans_map[paddr].addr;
+		if (pladdr == ADDR_EMPTY)
+			continue;
+
+		laddr = &rrpc->trans_map[pladdr];
+
+		if (paddr == laddr->addr) {
+			laddr->block = block;
+		} else {
+			set_bit(offset, block->invalid_pages);
+			block->nr_invalid_pages++;
+		}
+	}
+}
+
+static int rrpc_blocks_init(struct rrpc *rrpc)
+{
+	struct nvm_dev *dev = rrpc->q_nvm;
+	struct nvm_lun *lun;
+	struct nvm_block *blk;
+	sector_t lun_iter, blk_iter;
+
+	for (lun_iter = 0; lun_iter < rrpc->nr_luns; lun_iter++) {
+		lun = &dev->luns[lun_iter + rrpc->lun_offset];
+
+		lun_for_each_block(lun, blk, blk_iter)
+			rrpc_block_map_update(rrpc, blk);
+	}
+
+	return 0;
+}
+
+static int rrpc_luns_configure(struct rrpc *rrpc)
+{
+	struct rrpc_lun *rlun;
+	struct nvm_block *blk;
+	int i;
+
+	for (i = 0; i < rrpc->nr_luns; i++) {
+		rlun = &rrpc->luns[i];
+
+		blk = nvm_get_blk(rlun->parent, 0);
+		if (!blk)
+			return -EINVAL;
+
+		rrpc_set_lun_cur(rlun, blk);
+
+		/* Emergency gc block */
+		blk = nvm_get_blk(rlun->parent, 1);
+		if (!blk)
+			return -EINVAL;
+		rlun->gc_cur = blk;
+	}
+
+	return 0;
+}
+
+static struct nvm_target_type tt_rrpc;
+
+static void *rrpc_init(struct gendisk *bdisk, struct gendisk *tdisk,
+						int lun_begin, int lun_end)
+{
+	struct request_queue *bqueue = bdisk->queue;
+	struct request_queue *tqueue = tdisk->queue;
+	struct nvm_dev *dev;
+	struct block_device *bdev;
+	struct rrpc *rrpc;
+	int ret;
+
+	if (!nvm_get_dev(bdisk)) {
+		pr_err("nvm: block device not supported.\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	bdev = bdget_disk(bdisk, 0);
+	if (blkdev_get(bdev, FMODE_WRITE | FMODE_READ, NULL)) {
+		pr_err("nvm: could not access backing device\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	dev = nvm_get_dev(bdisk);
+
+	rrpc = kzalloc(sizeof(struct rrpc), GFP_KERNEL);
+	if (!rrpc) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	rrpc->q_dev = bqueue;
+	rrpc->q_nvm = bdisk->nvm;
+	rrpc->q_bdev = bdev;
+	rrpc->nr_luns = lun_end - lun_begin + 1;
+	rrpc->instance.tt = &tt_rrpc;
+
+	/* simple round-robin strategy */
+	atomic_set(&rrpc->next_lun, -1);
+
+	ret = rrpc_luns_init(rrpc, lun_begin, lun_end);
+	if (ret) {
+		pr_err("nvm: could not initialize luns\n");
+		goto err;
+	}
+
+	rrpc->poffset = rrpc->luns[0].parent->nr_blocks *
+			rrpc->luns[0].parent->nr_pages_per_blk * lun_begin;
+	rrpc->lun_offset = lun_begin;
+
+	ret = rrpc_core_init(rrpc);
+	if (ret) {
+		pr_err("nvm: rrpc: could not initialize core\n");
+		goto err;
+	}
+
+	ret = rrpc_map_init(rrpc);
+	if (ret) {
+		pr_err("nvm: rrpc: could not initialize maps\n");
+		goto err;
+	}
+
+	ret = rrpc_blocks_init(rrpc);
+	if (ret) {
+		pr_err("nvm: rrpc: could not initialize state for blocks\n");
+		goto err;
+	}
+
+	ret = rrpc_luns_configure(rrpc);
+	if (ret) {
+		pr_err("nvm: rrpc: not enough blocks available in LUNs.\n");
+		goto err;
+	}
+
+	ret = rrpc_gc_init(rrpc);
+	if (ret) {
+		pr_err("nvm: rrpc: could not initialize gc\n");
+		goto err;
+	}
+
+	/* make sure to inherit the size from the underlying device */
+	blk_queue_logical_block_size(tqueue, queue_physical_block_size(bqueue));
+	blk_queue_max_hw_sectors(tqueue, queue_max_hw_sectors(bqueue));
+
+	pr_info("nvm: rrpc initialized with %u luns and %llu pages.\n",
+			rrpc->nr_luns, (unsigned long long)rrpc->nr_pages);
+
+	mod_timer(&rrpc->gc_timer, jiffies + msecs_to_jiffies(10));
+
+	return rrpc;
+err:
+	blkdev_put(bdev, FMODE_WRITE | FMODE_READ);
+	rrpc_free(rrpc);
+	return ERR_PTR(ret);
+}
+
+/* round robin, page-based FTL, and cost-based GC */
+static struct nvm_target_type tt_rrpc = {
+	.name		= "rrpc",
+
+	.make_rq	= rrpc_make_rq,
+	.prep_rq	= rrpc_prep_rq,
+	.unprep_rq	= rrpc_unprep_rq,
+
+	.capacity	= rrpc_capacity,
+
+	.init		= rrpc_init,
+	.exit		= rrpc_exit,
+};
+
+static int __init rrpc_module_init(void)
+{
+	return nvm_register_target(&tt_rrpc);
+}
+
+static void rrpc_module_exit(void)
+{
+	nvm_unregister_target(&tt_rrpc);
+}
+
+module_init(rrpc_module_init);
+module_exit(rrpc_module_exit);
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Round-Robin Cost-based Hybrid Layer for Open-Channel SSDs");
diff --git a/drivers/lightnvm/rrpc.h b/drivers/lightnvm/rrpc.h
new file mode 100644
index 0000000..d8b1588
--- /dev/null
+++ b/drivers/lightnvm/rrpc.h
@@ -0,0 +1,221 @@ 
+/*
+ * Copyright (C) 2015 IT University of Copenhagen
+ * Initial release: Matias Bjorling <mabj@itu.dk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * Implementation of a Round-robin page-based Hybrid FTL for Open-channel SSDs.
+ */
+
+#ifndef RRPC_H_
+#define RRPC_H_
+
+#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+
+#include <linux/lightnvm.h>
+
+/* We partition the namespace of translation map into these pieces for tracking
+ * in-flight addresses. */
+#define NVM_INFLIGHT_PARTITIONS 1
+
+/* Run only GC if less than 1/X blocks are free */
+#define GC_LIMIT_INVERSE 10
+#define GC_TIME_SECS 100
+
+struct nvm_inflight {
+	spinlock_t lock;
+	struct list_head reqs;
+};
+
+struct rrpc_lun;
+
+struct rrpc_block {
+	struct nvm_block *parent;
+	struct list_head prio;
+};
+
+struct rrpc_lun {
+	struct rrpc *rrpc;
+	struct nvm_lun *parent;
+	struct nvm_block *cur, *gc_cur;
+	struct rrpc_block *blocks;	/* Reference to block allocation */
+	struct list_head prio_list;		/* Blocks that may be GC'ed */
+	struct work_struct ws_gc;
+
+	int nr_blocks;
+	spinlock_t lock;
+};
+
+struct rrpc {
+	/* instance must be kept in top to resolve rrpc in prep/unprep */
+	struct nvm_target_instance instance;
+
+	struct nvm_dev *q_nvm;
+	struct request_queue *q_dev;
+	struct block_device *q_bdev;
+
+	int nr_luns;
+	int lun_offset;
+	sector_t poffset; /* physical page offset */
+
+	struct rrpc_lun *luns;
+
+	/* calculated values */
+	unsigned long nr_pages;
+	unsigned long total_blocks;
+
+	/* Write strategy variables. Move these into each for structure for each
+	 * strategy */
+	atomic_t next_lun; /* Whenever a page is written, this is updated
+			    * to point to the next write lun */
+
+	/* Simple translation map of logical addresses to physical addresses.
+	 * The logical addresses is known by the host system, while the physical
+	 * addresses are used when writing to the disk block device. */
+	struct nvm_addr *trans_map;
+	/* also store a reverse map for garbage collection */
+	struct nvm_rev_addr *rev_trans_map;
+	spinlock_t rev_lock;
+
+	struct nvm_inflight inflight_map[NVM_INFLIGHT_PARTITIONS];
+
+	mempool_t *addr_pool;
+	mempool_t *page_pool;
+	mempool_t *gcb_pool;
+
+	struct timer_list gc_timer;
+	struct workqueue_struct *krqd_wq;
+	struct workqueue_struct *kgc_wq;
+
+	struct gc_blocks *gblks;
+	struct gc_luns *gluns;
+};
+
+struct rrpc_block_gc {
+	struct rrpc *rrpc;
+	struct nvm_block *block;
+	struct work_struct ws_gc;
+};
+
+static inline sector_t nvm_get_laddr(struct request *rq)
+{
+	if (rq->special) {
+		struct nvm_internal_cmd *cmd = rq->special;
+
+		return cmd->phys_lba;
+	}
+
+	return blk_rq_pos(rq) / NR_PHY_IN_LOG;
+}
+
+static inline sector_t nvm_get_sector(sector_t laddr)
+{
+	return laddr * NR_PHY_IN_LOG;
+}
+
+static inline struct nvm_per_rq *get_per_rq_data(struct request *rq)
+{
+	struct request_queue *q = rq->q;
+
+	return blk_mq_rq_to_pdu(rq) + q->tag_set->cmd_size -
+						sizeof(struct nvm_per_rq);
+}
+
+static inline int request_intersects(struct rrpc_inflight_rq *r,
+				sector_t laddr_start, sector_t laddr_end)
+{
+	return (laddr_end >= r->l_start && laddr_end <= r->l_end) &&
+		(laddr_start >= r->l_start && laddr_start <= r->l_end);
+}
+
+static int __rrpc_lock_laddr(struct rrpc *rrpc, sector_t laddr,
+			     unsigned pages, struct rrpc_inflight_rq *r)
+{
+	struct nvm_inflight *map =
+			&rrpc->inflight_map[laddr % NVM_INFLIGHT_PARTITIONS];
+	sector_t laddr_end = laddr + pages - 1;
+	struct rrpc_inflight_rq *rtmp;
+
+	spin_lock_irq(&map->lock);
+	list_for_each_entry(rtmp, &map->reqs, list) {
+		if (unlikely(request_intersects(rtmp, laddr, laddr_end))) {
+			/* existing, overlapping request, come back later */
+			spin_unlock_irq(&map->lock);
+			return 1;
+		}
+	}
+
+	r->l_start = laddr;
+	r->l_end = laddr_end;
+
+	list_add_tail(&r->list, &map->reqs);
+	spin_unlock_irq(&map->lock);
+	return 0;
+}
+
+static inline int rrpc_lock_laddr(struct rrpc *rrpc, sector_t laddr,
+				 unsigned pages,
+				 struct rrpc_inflight_rq *r)
+{
+	BUG_ON((laddr + pages) > rrpc->nr_pages);
+
+	return __rrpc_lock_laddr(rrpc, laddr, pages, r);
+}
+
+static inline struct rrpc_inflight_rq *rrpc_get_inflight_rq(struct request *rq)
+{
+	struct nvm_per_rq *pd = get_per_rq_data(rq);
+
+	return &pd->inflight_rq;
+}
+
+static inline int rrpc_lock_rq(struct rrpc *rrpc, struct request *rq)
+{
+	sector_t laddr = nvm_get_laddr(rq);
+	unsigned int pages = blk_rq_bytes(rq) / EXPOSED_PAGE_SIZE;
+	struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rq);
+
+	if (rq->special)
+		return 0;
+
+	return rrpc_lock_laddr(rrpc, laddr, pages, r);
+}
+
+static inline void rrpc_unlock_laddr(struct rrpc *rrpc, sector_t laddr,
+				    struct rrpc_inflight_rq *r)
+{
+	struct nvm_inflight *map =
+			&rrpc->inflight_map[laddr % NVM_INFLIGHT_PARTITIONS];
+	unsigned long flags;
+
+	spin_lock_irqsave(&map->lock, flags);
+	list_del_init(&r->list);
+	spin_unlock_irqrestore(&map->lock, flags);
+}
+
+static inline void rrpc_unlock_rq(struct rrpc *rrpc, struct request *rq)
+{
+	sector_t laddr = nvm_get_laddr(rq);
+	unsigned int pages = blk_rq_bytes(rq) / EXPOSED_PAGE_SIZE;
+	struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rq);
+
+	BUG_ON((laddr + pages) > rrpc->nr_pages);
+
+	if (rq->special)
+		return;
+
+	rrpc_unlock_laddr(rrpc, laddr, r);
+}
+
+#endif /* RRPC_H_ */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0283c7e..5635940 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1471,6 +1471,8 @@  extern bool blk_integrity_merge_bio(struct request_queue *, struct request *,
 static inline
 struct blk_integrity *bdev_get_integrity(struct block_device *bdev)
 {
+	if (unlikely(!bdev))
+		return NULL;
 	return bdev->bd_disk->integrity;
 }