[PATCH 22/25] lightnvm: core on-disk initialization

[Matias BjÃrling]

An Open-Channel SSD shall be initialized before use. To initialize, we
define an on-disk format, that keeps a small set of metadata to bring up
the media manager on top of the device.

The initial step is introduced to allow a user to format the disks for a
given media manager. During format, a system block is stored on one to
three separate luns on the device. Each lun has the system block
duplicated. During initialization, the system block can be retrieved and
the appropriate media manager can initialized.

The on-disk format currently covers (struct nvm_system_block):

 - Magic value "NVMS".
 - Monotonic increasing sequence number.
 - The physical block erase count.
 - Version of the system block format.
 - Media manager type.
 - Media manager superblock physical address.

The interface provides three functions to manage the system block:

 int nvm_init_sysblock(struct nvm_dev *, struct nvm_sb_info *)
 int nvm_get_sysblock(struct nvm *dev, struct nvm_sb_info *)
 int nvm_update_sysblock(struct nvm *dev, struct nvm_sb_info *)

Each implement a part of the logic to manage the system block. The
initialization creates the first system blocks and mark them on the
device. Get retrieves the latest system block by scanning all pages in
the associated system blocks. The update sysblock writes new metadata
and allocates new block if necessary.

Signed-off-by: Matias BjÃrling <m@xxxxxxxxxxx>
---
 drivers/lightnvm/Makefile     |   2 +-
 drivers/lightnvm/core.c       |   1 +
 drivers/lightnvm/sysblk.c     | 562 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/lightnvm.h      |  35 +++
 include/uapi/linux/lightnvm.h |   1 +
 5 files changed, 600 insertions(+), 1 deletion(-)
 create mode 100644 drivers/lightnvm/sysblk.c

diff --git a/drivers/lightnvm/Makefile b/drivers/lightnvm/Makefile
index 7e0f42a..a7a0a22 100644
--- a/drivers/lightnvm/Makefile
+++ b/drivers/lightnvm/Makefile
@@ -2,6 +2,6 @@
 # Makefile for Open-Channel SSDs.
 #
 
-obj-$(CONFIG_NVM)		:= core.o
+obj-$(CONFIG_NVM)		:= core.o sysblk.o
 obj-$(CONFIG_NVM_GENNVM) 	+= gennvm.o
 obj-$(CONFIG_NVM_RRPC)		+= rrpc.o
diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
index 1f302cc..73b8ae1 100644
--- a/drivers/lightnvm/core.c
+++ b/drivers/lightnvm/core.c
@@ -466,6 +466,7 @@ static int nvm_core_init(struct nvm_dev *dev)
 				dev->nr_chnls;
 	dev->total_pages = dev->total_blocks * dev->pgs_per_blk;
 	INIT_LIST_HEAD(&dev->online_targets);
+	mutex_init(&dev->mlock);
 
 	return 0;
 }
diff --git a/drivers/lightnvm/sysblk.c b/drivers/lightnvm/sysblk.c
new file mode 100644
index 0000000..b8489f4
--- /dev/null
+++ b/drivers/lightnvm/sysblk.c
@@ -0,0 +1,562 @@
+/*
+ * Copyright (C) 2015 Matias Bjorling. All rights reserved.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
+ * USA.
+ *
+ */
+
+#include <linux/lightnvm.h>
+
+#define MAX_SYSBLKS 3	/* remember to update mapping scheme on change */
+#define MAX_BLKS_PR_SYSBLK 2 /* 2 blks with 256 pages and 3000 erases
+			      * enables ~1.5M updates per sysblk unit
+			      */
+
+struct sysblk_scan {
+	/* A row is a collection of flash blocks for a system block. */
+	int nr_rows;
+	int row;
+	int act_blk[MAX_SYSBLKS];
+
+	int nr_ppas;
+	struct ppa_addr ppas[MAX_SYSBLKS * MAX_BLKS_PR_SYSBLK];/* all sysblks */
+};
+
+static inline int scan_ppa_idx(int row, int blkid)
+{
+	return (row * MAX_BLKS_PR_SYSBLK) + blkid;
+}
+
+void nvm_sysblk_to_cpu(struct nvm_sb_info *info, struct nvm_system_block *sb)
+{
+	info->seqnr = be32_to_cpu(sb->seqnr);
+	info->erase_cnt = be32_to_cpu(sb->erase_cnt);
+	info->version = be16_to_cpu(sb->version);
+	strncpy(info->mmtype, sb->mmtype, NVM_MMTYPE_LEN);
+	info->fs_ppa.ppa = be64_to_cpu(sb->fs_ppa);
+}
+
+void nvm_cpu_to_sysblk(struct nvm_system_block *sb, struct nvm_sb_info *info)
+{
+	sb->magic = cpu_to_be32(NVM_SYSBLK_MAGIC);
+	sb->seqnr = cpu_to_be32(info->seqnr);
+	sb->erase_cnt = cpu_to_be32(info->erase_cnt);
+	sb->version = cpu_to_be16(info->version);
+	strncpy(sb->mmtype, info->mmtype, NVM_MMTYPE_LEN);
+	sb->fs_ppa = cpu_to_be64(info->fs_ppa.ppa);
+}
+
+static int nvm_setup_sysblks(struct nvm_dev *dev, struct ppa_addr *sysblk_ppas)
+{
+	int nr_rows = min_t(int, MAX_SYSBLKS, dev->nr_chnls);
+	int i;
+
+	for (i = 0; i < nr_rows; i++)
+		sysblk_ppas[i].ppa = 0;
+
+	/* if possible, place sysblk at first channel, middle channel and last
+	 * channel of the device. If not, create only one or two sys blocks
+	 */
+	switch (dev->nr_chnls) {
+	case 2:
+		sysblk_ppas[1].g.ch = 1;
+		/* fall-through */
+	case 1:
+		sysblk_ppas[0].g.ch = 0;
+		break;
+	default:
+		sysblk_ppas[0].g.ch = 0;
+		sysblk_ppas[1].g.ch = dev->nr_chnls / 2;
+		sysblk_ppas[2].g.ch = dev->nr_chnls - 1;
+		break;
+	}
+
+	return nr_rows;
+}
+
+void nvm_setup_sysblk_scan(struct nvm_dev *dev, struct sysblk_scan *s,
+						struct ppa_addr *sysblk_ppas)
+{
+	memset(s, 0, sizeof(struct sysblk_scan));
+	s->nr_rows = nvm_setup_sysblks(dev, sysblk_ppas);
+}
+
+static int sysblk_get_host_blks(struct ppa_addr ppa, int nr_blks, u8 *blks,
+								void *private)
+{
+	struct sysblk_scan *s = private;
+	int i, nr_sysblk = 0;
+
+	for (i = 0; i < nr_blks; i++) {
+		if (blks[i] != NVM_BLK_T_HOST)
+			continue;
+
+		if (s->nr_ppas == MAX_BLKS_PR_SYSBLK * MAX_SYSBLKS) {
+			pr_err("nvm: too many host blks\n");
+			return -EINVAL;
+		}
+
+		ppa.g.blk = i;
+
+		s->ppas[scan_ppa_idx(s->row, nr_sysblk)] = ppa;
+		s->nr_ppas++;
+		nr_sysblk++;
+	}
+
+	return 0;
+}
+
+static int nvm_get_all_sysblks(struct nvm_dev *dev, struct sysblk_scan *s,
+				struct ppa_addr *ppas, nvm_bb_update_fn *fn)
+{
+	struct ppa_addr dppa;
+	int i, ret;
+
+	s->nr_ppas = 0;
+
+	for (i = 0; i < s->nr_rows; i++) {
+		dppa = generic_to_dev_addr(dev, ppas[i]);
+		s->row = i;
+
+		ret = dev->ops->get_bb_tbl(dev, dppa, dev->blks_per_lun, fn, s);
+		if (ret) {
+			pr_err("nvm: failed bb tbl for ppa (%u %u)\n",
+							ppas[i].g.ch,
+							ppas[i].g.blk);
+			return ret;
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * scans a block for latest sysblk.
+ * Returns:
+ *	0 - newer sysblk not found. PPA is updated to latest page.
+ *	1 - newer sysblk found and stored in *cur. PPA is updated to
+ *	    next valid page.
+ *	<0- error.
+ */
+static int nvm_scan_block(struct nvm_dev *dev, struct ppa_addr *ppa,
+						struct nvm_system_block *sblk)
+{
+	struct nvm_system_block *cur;
+	int pg, cursz, ret, found = 0;
+
+	/* the full buffer for a flash page is allocated. Only the first of it
+	 * contains the system block information
+	 */
+	cursz = dev->sec_size * dev->sec_per_pg * dev->nr_planes;
+	cur = kmalloc(cursz, GFP_KERNEL);
+	if (!cur)
+		return -ENOMEM;
+
+	/* perform linear scan through the block */
+	for (pg = 0; pg < dev->lps_per_blk; pg++) {
+		ppa->g.pg = ppa_to_slc(dev, pg);
+
+		ret = nvm_submit_ppa(dev, ppa, 1, NVM_OP_PREAD, NVM_IO_SLC_MODE,
+								cur, cursz);
+		if (ret) {
+			if (ret == NVM_RSP_ERR_EMPTYPAGE) {
+				pr_debug("nvm: sysblk scan empty ppa (%u %u %u %u)\n",
+							ppa->g.ch,
+							ppa->g.lun,
+							ppa->g.blk,
+							ppa->g.pg);
+				break;
+			}
+			pr_err("nvm: read failed (%x) for ppa (%u %u %u %u)",
+							ret,
+							ppa->g.ch,
+							ppa->g.lun,
+							ppa->g.blk,
+							ppa->g.pg);
+			break; /* if we can't read a page, continue to the
+				* next blk
+				*/
+		}
+
+		if (be32_to_cpu(cur->magic) != NVM_SYSBLK_MAGIC) {
+			pr_debug("nvm: scan break for ppa (%u %u %u %u)\n",
+							ppa->g.ch,
+							ppa->g.lun,
+							ppa->g.blk,
+							ppa->g.pg);
+			break; /* last valid page already found */
+		}
+
+		if (be32_to_cpu(cur->seqnr) < be32_to_cpu(sblk->seqnr))
+			continue;
+
+		memcpy(sblk, cur, sizeof(struct nvm_system_block));
+		found = 1;
+	}
+
+	kfree(cur);
+
+	return found;
+}
+
+static int nvm_set_bb_tbl(struct nvm_dev *dev, struct sysblk_scan *s, int type)
+{
+	struct nvm_rq rqd;
+	int ret;
+
+	if (s->nr_ppas > dev->ops->max_phys_sect) {
+		pr_err("nvm: unable to update all sysblocks atomically\n");
+		return -EINVAL;
+	}
+
+	memset(&rqd, 0, sizeof(struct nvm_rq));
+
+	nvm_set_rqd_ppalist(dev, &rqd, s->ppas, s->nr_ppas);
+	nvm_generic_to_addr_mode(dev, &rqd);
+
+	ret = dev->ops->set_bb_tbl(dev, &rqd, type);
+	nvm_free_rqd_ppalist(dev, &rqd);
+	if (ret) {
+		pr_err("nvm: sysblk failed bb mark\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int sysblk_get_free_blks(struct ppa_addr ppa, int nr_blks, u8 *blks,
+								void *private)
+{
+	struct sysblk_scan *s = private;
+	struct ppa_addr *sppa;
+	int i, blkid = 0;
+
+	for (i = 0; i < nr_blks; i++) {
+		if (blks[i] == NVM_BLK_T_HOST)
+			return -EEXIST;
+
+		if (blks[i] != NVM_BLK_T_FREE)
+			continue;
+
+		sppa = &s->ppas[scan_ppa_idx(s->row, blkid)];
+		sppa->g.ch = ppa.g.ch;
+		sppa->g.lun = ppa.g.lun;
+		sppa->g.blk = i;
+		s->nr_ppas++;
+		blkid++;
+
+		pr_debug("nvm: use (%u %u %u) as sysblk\n",
+					sppa->g.ch, sppa->g.lun, sppa->g.blk);
+		if (blkid > MAX_BLKS_PR_SYSBLK - 1)
+			return 0;
+	}
+
+	pr_err("nvm: sysblk failed get sysblk\n");
+	return -EINVAL;
+}
+
+static int nvm_write_and_verify(struct nvm_dev *dev, struct nvm_sb_info *info,
+							struct sysblk_scan *s)
+{
+	struct nvm_system_block nvmsb;
+	void *buf;
+	int i, sect, ret, bufsz;
+	struct ppa_addr *ppas;
+
+	nvm_cpu_to_sysblk(&nvmsb, info);
+
+	/* buffer for flash page */
+	bufsz = dev->sec_size * dev->sec_per_pg * dev->nr_planes;
+	buf = kzalloc(bufsz, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+	memcpy(buf, &nvmsb, sizeof(struct nvm_system_block));
+
+	ppas = kcalloc(dev->sec_per_pg, sizeof(struct ppa_addr), GFP_KERNEL);
+	if (!ppas) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	/* Write and verify */
+	for (i = 0; i < s->nr_rows; i++) {
+		ppas[0] = s->ppas[scan_ppa_idx(i, s->act_blk[i])];
+
+		pr_debug("nvm: writing sysblk to ppa (%u %u %u %u)\n",
+							ppas[0].g.ch,
+							ppas[0].g.lun,
+							ppas[0].g.blk,
+							ppas[0].g.pg);
+
+		/* Expand to all sectors within a flash page */
+		if (dev->sec_per_pg > 1) {
+			for (sect = 1; sect < dev->sec_per_pg; sect++) {
+				ppas[sect].ppa = ppas[0].ppa;
+				ppas[sect].g.sec = sect;
+			}
+		}
+
+		ret = nvm_submit_ppa(dev, ppas, dev->sec_per_pg, NVM_OP_PWRITE,
+						NVM_IO_SLC_MODE, buf, bufsz);
+		if (ret) {
+			pr_err("nvm: sysblk failed program (%u %u %u)\n",
+							ppas[0].g.ch,
+							ppas[0].g.lun,
+							ppas[0].g.blk);
+			break;
+		}
+
+		ret = nvm_submit_ppa(dev, ppas, dev->sec_per_pg, NVM_OP_PREAD,
+						NVM_IO_SLC_MODE, buf, bufsz);
+		if (ret) {
+			pr_err("nvm: sysblk failed read (%u %u %u)\n",
+							ppas[0].g.ch,
+							ppas[0].g.lun,
+							ppas[0].g.blk);
+			break;
+		}
+
+		if (memcmp(buf, &nvmsb, sizeof(struct nvm_system_block))) {
+			pr_err("nvm: sysblk failed verify (%u %u %u)\n",
+							ppas[0].g.ch,
+							ppas[0].g.lun,
+							ppas[0].g.blk);
+			ret = -EINVAL;
+			break;
+		}
+	}
+
+	kfree(ppas);
+err:
+	kfree(buf);
+
+	return ret;
+}
+
+static int nvm_prepare_new_sysblks(struct nvm_dev *dev, struct sysblk_scan *s)
+{
+	int i, ret;
+	unsigned long nxt_blk;
+	struct ppa_addr *ppa;
+
+	for (i = 0; i < s->nr_rows; i++) {
+		nxt_blk = (s->act_blk[i] + 1) % MAX_BLKS_PR_SYSBLK;
+		ppa = &s->ppas[scan_ppa_idx(i, nxt_blk)];
+		ppa->g.pg = ppa_to_slc(dev, 0);
+
+		ret = nvm_erase_ppa(dev, ppa, 1);
+		if (ret)
+			return ret;
+
+		s->act_blk[i] = nxt_blk;
+	}
+
+	return 0;
+}
+
+int nvm_get_sysblock(struct nvm_dev *dev, struct nvm_sb_info *info)
+{
+	struct ppa_addr sysblk_ppas[MAX_SYSBLKS];
+	struct sysblk_scan s;
+	struct nvm_system_block *cur;
+	int i, j, found = 0;
+	int ret = -ENOMEM;
+
+	/*
+	 * 1. setup sysblk locations
+	 * 2. get bad block list
+	 * 3. filter on host-specific (type 3)
+	 * 4. iterate through all and find the highest seq nr.
+	 * 5. return superblock information
+	 */
+
+	if (!dev->ops->get_bb_tbl)
+		return -EINVAL;
+
+	nvm_setup_sysblk_scan(dev, &s, sysblk_ppas);
+
+	mutex_lock(&dev->mlock);
+	ret = nvm_get_all_sysblks(dev, &s, sysblk_ppas, sysblk_get_host_blks);
+	if (ret)
+		goto err_sysblk;
+
+	/* no sysblocks initialized */
+	if (!s.nr_ppas)
+		goto err_sysblk;
+
+	cur = kzalloc(sizeof(struct nvm_system_block), GFP_KERNEL);
+	if (!cur)
+		goto err_sysblk;
+
+	/* find the latest block across all sysblocks */
+	for (i = 0; i < s.nr_rows; i++) {
+		for (j = 0; j < MAX_BLKS_PR_SYSBLK; j++) {
+			struct ppa_addr ppa = s.ppas[scan_ppa_idx(i, j)];
+
+			ret = nvm_scan_block(dev, &ppa, cur);
+			if (ret > 0)
+				found = 1;
+			else if (ret < 0)
+				break;
+		}
+	}
+
+	nvm_sysblk_to_cpu(info, cur);
+
+	kfree(cur);
+err_sysblk:
+	mutex_unlock(&dev->mlock);
+
+	if (found)
+		return 1;
+	return ret;
+}
+
+int nvm_update_sysblock(struct nvm_dev *dev, struct nvm_sb_info *new)
+{
+	/* 1. for each latest superblock
+	 * 2. if room
+	 *    a. write new flash page entry with the updated information
+	 * 3. if no room
+	 *    a. find next available block on lun (linear search)
+	 *       if none, continue to next lun
+	 *       if none at all, report error. also report that it wasn't
+	 *       possible to write to all superblocks.
+	 *    c. write data to block.
+	 */
+	struct ppa_addr sysblk_ppas[MAX_SYSBLKS];
+	struct sysblk_scan s;
+	struct nvm_system_block *cur;
+	int i, j, ppaidx, found = 0;
+	int ret = -ENOMEM;
+
+	if (!dev->ops->get_bb_tbl)
+		return -EINVAL;
+
+	nvm_setup_sysblk_scan(dev, &s, sysblk_ppas);
+
+	mutex_lock(&dev->mlock);
+	ret = nvm_get_all_sysblks(dev, &s, sysblk_ppas, sysblk_get_host_blks);
+	if (ret)
+		goto err_sysblk;
+
+	cur = kzalloc(sizeof(struct nvm_system_block), GFP_KERNEL);
+	if (!cur)
+		goto err_sysblk;
+
+	/* Get the latest sysblk for each sysblk row */
+	for (i = 0; i < s.nr_rows; i++) {
+		found = 0;
+		for (j = 0; j < MAX_BLKS_PR_SYSBLK; j++) {
+			ppaidx = scan_ppa_idx(i, j);
+			ret = nvm_scan_block(dev, &s.ppas[ppaidx], cur);
+			if (ret > 0) {
+				s.act_blk[i] = j;
+				found = 1;
+			} else if (ret < 0)
+				break;
+		}
+	}
+
+	if (!found) {
+		pr_err("nvm: no valid sysblks found to update\n");
+		ret = -EINVAL;
+		goto err_cur;
+	}
+
+	/*
+	 * All sysblocks found. Check that they have same page id in their flash
+	 * blocks
+	 */
+	for (i = 1; i < s.nr_rows; i++) {
+		struct ppa_addr l = s.ppas[scan_ppa_idx(0, s.act_blk[0])];
+		struct ppa_addr r = s.ppas[scan_ppa_idx(i, s.act_blk[i])];
+
+		if (l.g.pg != r.g.pg) {
+			pr_err("nvm: sysblks not on same page. Previous update failed.\n");
+			ret = -EINVAL;
+			goto err_cur;
+		}
+	}
+
+	/*
+	 * Check that there haven't been another update to the seqnr since we
+	 * began
+	 */
+	if ((new->seqnr - 1) != be32_to_cpu(cur->seqnr)) {
+		pr_err("nvm: seq is not sequential\n");
+		ret = -EINVAL;
+		goto err_cur;
+	}
+
+	/*
+	 * When all pages in a block has been written, a new block is selected
+	 * and writing is performed on the new block.
+	 */
+	if (s.ppas[scan_ppa_idx(0, s.act_blk[0])].g.pg ==
+						dev->lps_per_blk - 1) {
+		ret = nvm_prepare_new_sysblks(dev, &s);
+		if (ret)
+			goto err_cur;
+	}
+
+	ret = nvm_write_and_verify(dev, new, &s);
+err_cur:
+	kfree(cur);
+err_sysblk:
+	mutex_unlock(&dev->mlock);
+
+	return ret;
+}
+
+int nvm_init_sysblock(struct nvm_dev *dev, struct nvm_sb_info *info)
+{
+	struct ppa_addr sysblk_ppas[MAX_SYSBLKS];
+	struct sysblk_scan s;
+	int ret;
+
+	/*
+	 * 1. select master blocks and select first available blks
+	 * 2. get bad block list
+	 * 3. mark MAX_SYSBLKS block as host-based device allocated.
+	 * 4. write and verify data to block
+	 */
+
+	if (!dev->ops->get_bb_tbl || !dev->ops->set_bb_tbl)
+		return -EINVAL;
+
+	if (!(dev->mccap & NVM_ID_CAP_SLC) || !dev->lps_per_blk) {
+		pr_err("nvm: memory does not support SLC access\n");
+		return -EINVAL;
+	}
+
+	/* Index all sysblocks and mark them as host-driven */
+	nvm_setup_sysblk_scan(dev, &s, sysblk_ppas);
+
+	mutex_lock(&dev->mlock);
+	ret = nvm_get_all_sysblks(dev, &s, sysblk_ppas, sysblk_get_free_blks);
+	if (ret)
+		goto err_mark;
+
+	ret = nvm_set_bb_tbl(dev, &s, NVM_BLK_T_HOST);
+	if (ret)
+		goto err_mark;
+
+	/* Write to the first block of each row */
+	ret = nvm_write_and_verify(dev, info, &s);
+err_mark:
+	mutex_unlock(&dev->mlock);
+	return ret;
+}
diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
index 678fd91..7ad22d3 100644
--- a/include/linux/lightnvm.h
+++ b/include/linux/lightnvm.h
@@ -17,6 +17,7 @@ enum {
 #include <linux/types.h>
 #include <linux/file.h>
 #include <linux/dmapool.h>
+#include <uapi/linux/lightnvm.h>
 
 enum {
 	/* HW Responsibilities */
@@ -281,6 +282,15 @@ struct nvm_block {
 	int state;
 };
 
+/* system block cpu representation */
+struct nvm_sb_info {
+	unsigned long		seqnr;
+	unsigned long		erase_cnt;
+	unsigned int		version;
+	char			mmtype[NVM_MMTYPE_LEN];
+	struct ppa_addr		fs_ppa;
+};
+
 struct nvm_dev {
 	struct nvm_dev_ops *ops;
 
@@ -329,6 +339,8 @@ struct nvm_dev {
 	/* Backend device */
 	struct request_queue *q;
 	char name[DISK_NAME_LEN];
+
+	struct mutex mlock;
 };
 
 static inline struct ppa_addr generic_to_dev_addr(struct nvm_dev *dev,
@@ -394,6 +406,11 @@ static inline struct ppa_addr block_to_ppa(struct nvm_dev *dev,
 	return ppa;
 }
 
+static inline int ppa_to_slc(struct nvm_dev *dev, int slc_pg)
+{
+	return dev->lptbl[slc_pg];
+}
+
 typedef blk_qc_t (nvm_tgt_make_rq_fn)(struct request_queue *, struct bio *);
 typedef sector_t (nvm_tgt_capacity_fn)(void *);
 typedef void *(nvm_tgt_init_fn)(struct nvm_dev *, struct gendisk *, int, int);
@@ -489,6 +506,24 @@ extern int nvm_erase_blk(struct nvm_dev *, struct nvm_block *);
 extern void nvm_end_io(struct nvm_rq *, int);
 extern int nvm_submit_ppa(struct nvm_dev *, struct ppa_addr *, int, int, int,
 								void *, int);
+
+/* sysblk.c */
+#define NVM_SYSBLK_MAGIC 0x4E564D53 /* "NVMS" */
+
+/* system block on disk representation */
+struct nvm_system_block {
+	__be32			magic;		/* magic signature */
+	__be32			seqnr;		/* sequence number */
+	__be32			erase_cnt;	/* erase count */
+	__be16			version;	/* version number */
+	u8			mmtype[NVM_MMTYPE_LEN]; /* media manager name */
+	__be64			fs_ppa;		/* PPA for media manager
+						 * superblock */
+};
+
+extern int nvm_get_sysblock(struct nvm_dev *, struct nvm_sb_info *);
+extern int nvm_update_sysblock(struct nvm_dev *, struct nvm_sb_info *);
+extern int nvm_init_sysblock(struct nvm_dev *, struct nvm_sb_info *);
 #else /* CONFIG_NVM */
 struct nvm_dev_ops;
 
diff --git a/include/uapi/linux/lightnvm.h b/include/uapi/linux/lightnvm.h
index 928f989..0171b85 100644
--- a/include/uapi/linux/lightnvm.h
+++ b/include/uapi/linux/lightnvm.h
@@ -33,6 +33,7 @@
 
 #define NVM_TTYPE_NAME_MAX 48
 #define NVM_TTYPE_MAX 63
+#define NVM_MMTYPE_LEN 8
 
 #define NVM_CTRL_FILE "/dev/lightnvm/control"
 
-- 
2.1.4