rrpc: Round-robin sector target with cost-based gc

This target allows an Open-Channel SSD to be exposed asas a block
device.

It implements a round-robin approach for sector allocation,
together with a greedy cost-based garbage collector.
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/Kconfig

@@ -32,4 +32,11 @@ config NVM_GENNVM
 	functionality to device, while keeping data placement and garbage
 	collection decisions on the host.
 
+config NVM_RRPC
+	tristate "Round-robin Hybrid Open-Channel SSD target"
+	---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

drivers/lightnvm/Makefile

@@ -4,3 +4,4 @@
 
 obj-$(CONFIG_NVM)		:= core.o
 obj-$(CONFIG_NVM_GENNVM) 	+= gennvm.o
+obj-$(CONFIG_NVM_RRPC)		+= rrpc.o

drivers/lightnvm/rrpc.h

+/*
+ * Copyright (C) 2015 IT University of Copenhagen
+ * Initial release: Matias Bjorling <m@bjorling.me>
+ *
+ * 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/vmalloc.h>
+
+#include <linux/lightnvm.h>
+
+/* Run only GC if less than 1/X blocks are free */
+#define GC_LIMIT_INVERSE 10
+#define GC_TIME_SECS 100
+
+#define RRPC_SECTOR (512)
+#define RRPC_EXPOSED_PAGE_SIZE (4096)
+
+#define NR_PHY_IN_LOG (RRPC_EXPOSED_PAGE_SIZE / RRPC_SECTOR)
+
+struct rrpc_inflight {
+	struct list_head reqs;
+	spinlock_t lock;
+};
+
+struct rrpc_inflight_rq {
+	struct list_head list;
+	sector_t l_start;
+	sector_t l_end;
+};
+
+struct rrpc_rq {
+	struct rrpc_inflight_rq inflight_rq;
+	struct rrpc_addr *addr;
+	unsigned long flags;
+};
+
+struct rrpc_block {
+	struct nvm_block *parent;
+	struct list_head prio;
+
+#define MAX_INVALID_PAGES_STORAGE 8
+	/* Bitmap for invalid page intries */
+	unsigned long invalid_pages[MAX_INVALID_PAGES_STORAGE];
+	/* points to the next writable page within a block */
+	unsigned int next_page;
+	/* number of pages that are invalid, wrt host page size */
+	unsigned int nr_invalid_pages;
+
+	spinlock_t lock;
+	atomic_t data_cmnt_size; /* data pages committed to stable storage */
+};
+
+struct rrpc_lun {
+	struct rrpc *rrpc;
+	struct nvm_lun *parent;
+	struct rrpc_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;
+
+	spinlock_t lock;
+};
+
+struct rrpc {
+	/* instance must be kept in top to resolve rrpc in unprep */
+	struct nvm_tgt_instance instance;
+
+	struct nvm_dev *dev;
+	struct gendisk *disk;
+
+	sector_t poffset; /* physical page offset */
+	int lun_offset;
+
+	int nr_luns;
+	struct rrpc_lun *luns;
+
+	/* calculated values */
+	unsigned long 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
+			    */
+
+	spinlock_t bio_lock;
+	struct bio_list requeue_bios;
+	struct work_struct ws_requeue;
+
+	/* 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 rrpc_addr *trans_map;
+	/* also store a reverse map for garbage collection */
+	struct rrpc_rev_addr *rev_trans_map;
+	spinlock_t rev_lock;
+
+	struct rrpc_inflight inflights;
+
+	mempool_t *addr_pool;
+	mempool_t *page_pool;
+	mempool_t *gcb_pool;
+	mempool_t *rq_pool;
+
+	struct timer_list gc_timer;
+	struct workqueue_struct *krqd_wq;
+	struct workqueue_struct *kgc_wq;
+};
+
+struct rrpc_block_gc {
+	struct rrpc *rrpc;
+	struct rrpc_block *rblk;
+	struct work_struct ws_gc;
+};
+
+/* Logical to physical mapping */
+struct rrpc_addr {
+	sector_t addr;
+	struct rrpc_block *rblk;
+};
+
+/* Physical to logical mapping */
+struct rrpc_rev_addr {
+	sector_t addr;
+};
+
+static inline sector_t rrpc_get_laddr(struct bio *bio)
+{
+	return bio->bi_iter.bi_sector / NR_PHY_IN_LOG;
+}
+
+static inline unsigned int rrpc_get_pages(struct bio *bio)
+{
+	return  bio->bi_iter.bi_size / RRPC_EXPOSED_PAGE_SIZE;
+}
+
+static inline sector_t rrpc_get_sector(sector_t laddr)
+{
+	return laddr * NR_PHY_IN_LOG;
+}
+
+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)
+{
+	sector_t laddr_end = laddr + pages - 1;
+	struct rrpc_inflight_rq *rtmp;
+
+	spin_lock_irq(&rrpc->inflights.lock);
+	list_for_each_entry(rtmp, &rrpc->inflights.reqs, list) {
+		if (unlikely(request_intersects(rtmp, laddr, laddr_end))) {
+			/* existing, overlapping request, come back later */
+			spin_unlock_irq(&rrpc->inflights.lock);
+			return 1;
+		}
+	}
+
+	r->l_start = laddr;
+	r->l_end = laddr_end;
+
+	list_add_tail(&r->list, &rrpc->inflights.reqs);
+	spin_unlock_irq(&rrpc->inflights.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 nvm_rq *rqd)
+{
+	struct rrpc_rq *rrqd = nvm_rq_to_pdu(rqd);
+
+	return &rrqd->inflight_rq;
+}
+
+static inline int rrpc_lock_rq(struct rrpc *rrpc, struct bio *bio,
+							struct nvm_rq *rqd)
+{
+	sector_t laddr = rrpc_get_laddr(bio);
+	unsigned int pages = rrpc_get_pages(bio);
+	struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rqd);
+
+	return rrpc_lock_laddr(rrpc, laddr, pages, r);
+}
+
+static inline void rrpc_unlock_laddr(struct rrpc *rrpc,
+						struct rrpc_inflight_rq *r)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&rrpc->inflights.lock, flags);
+	list_del_init(&r->list);
+	spin_unlock_irqrestore(&rrpc->inflights.lock, flags);
+}
+
+static inline void rrpc_unlock_rq(struct rrpc *rrpc, struct nvm_rq *rqd)
+{
+	struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rqd);
+	uint8_t pages = rqd->nr_pages;
+
+	BUG_ON((r->l_start + pages) > rrpc->nr_pages);
+
+	rrpc_unlock_laddr(rrpc, r);
+}
+
+#endif /* RRPC_H_ */