lightnvm: physical block device (pblk) target

This patch introduces pblk, a host-side translation layer for
Open-Channel SSDs to expose them like block devices. The translation
layer allows data placement decisions, and I/O scheduling to be
managed by the host, enabling users to optimize the SSD for their
specific workloads.

An open-channel SSD has a set of LUNs (parallel units) and a
collection of blocks. Each block can be read in any order, but
writes must be sequential. Writes may also fail, and if a block
requires it, must also be reset before new writes can be
applied.

To manage the constraints, pblk maintains a logical to
physical address (L2P) table,  write cache, garbage
collection logic, recovery scheme, and logic to rate-limit
user I/Os versus garbage collection I/Os.

The L2P table is fully-associative and manages sectors at a
4KB granularity. Pblk stores the L2P table in two places, in
the out-of-band area of the media and on the last page of a
line. In the cause of a power failure, pblk will perform a
scan to recover the L2P table.

The user data is organized into lines. A line is data
striped across blocks and LUNs. The lines enable the host to
reduce the amount of metadata to maintain besides the user
data and makes it easier to implement RAID or erasure coding
in the future.

pblk implements multi-tenant support and can be instantiated
multiple times on the same drive. Each instance owns a
portion of the SSD - both regarding I/O bandwidth and
capacity - providing I/O isolation for each case.

Finally, pblk also exposes a sysfs interface that allows
user-space to peek into the internals of pblk. The interface
is available at /dev/block/*/pblk/ where * is the block
device name exposed.

This work also contains contributions from:
  Matias Bjørling <matias@cnexlabs.com>
  Simon A. F. Lund <slund@cnexlabs.com>
  Young Tack Jin <youngtack.jin@gmail.com>
  Huaicheng Li <huaicheng@cs.uchicago.edu>

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 555 insertions, 0 deletions

diff --git a/drivers/lightnvm/pblk-gc.c b/drivers/lightnvm/pblk-gc.c
new file mode 100644
index 000000000000..9b147cfd8a41
--- /dev/null
+++ b/drivers/lightnvm/pblk-gc.c
@@ -0,0 +1,555 @@
+/*
+ * Copyright (C) 2016 CNEX Labs
+ * Initial release: Javier Gonzalez <javier@cnexlabs.com>
+ *                  Matias Bjorling <matias@cnexlabs.com>
+ *
+ * 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.
+ *
+ * pblk-gc.c - pblk's garbage collector
+ */
+
+#include "pblk.h"
+#include <linux/delay.h>
+
+static void pblk_gc_free_gc_rq(struct pblk_gc_rq *gc_rq)
+{
+	kfree(gc_rq->data);
+	kfree(gc_rq->lba_list);
+	kfree(gc_rq);
+}
+
+static int pblk_gc_write(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+	struct pblk_gc_rq *gc_rq, *tgc_rq;
+	LIST_HEAD(w_list);
+
+	spin_lock(&gc->w_lock);
+	if (list_empty(&gc->w_list)) {
+		spin_unlock(&gc->w_lock);
+		return 1;
+	}
+
+	list_for_each_entry_safe(gc_rq, tgc_rq, &gc->w_list, list) {
+		list_move_tail(&gc_rq->list, &w_list);
+		gc->w_entries--;
+	}
+	spin_unlock(&gc->w_lock);
+
+	list_for_each_entry_safe(gc_rq, tgc_rq, &w_list, list) {
+		pblk_write_gc_to_cache(pblk, gc_rq->data, gc_rq->lba_list,
+				gc_rq->nr_secs, gc_rq->secs_to_gc,
+				gc_rq->line, PBLK_IOTYPE_GC);
+
+		kref_put(&gc_rq->line->ref, pblk_line_put);
+
+		list_del(&gc_rq->list);
+		pblk_gc_free_gc_rq(gc_rq);
+	}
+
+	return 0;
+}
+
+static void pblk_gc_writer_kick(struct pblk_gc *gc)
+{
+	wake_up_process(gc->gc_writer_ts);
+}
+
+/*
+ * Responsible for managing all memory related to a gc request. Also in case of
+ * failure
+ */
+static int pblk_gc_move_valid_secs(struct pblk *pblk, struct pblk_line *line,
+				   u64 *lba_list, unsigned int nr_secs)
+{
+	struct nvm_tgt_dev *dev = pblk->dev;
+	struct nvm_geo *geo = &dev->geo;
+	struct pblk_gc *gc = &pblk->gc;
+	struct pblk_gc_rq *gc_rq;
+	void *data;
+	unsigned int secs_to_gc;
+	int ret = NVM_IO_OK;
+
+	data = kmalloc(nr_secs * geo->sec_size, GFP_KERNEL);
+	if (!data) {
+		ret = NVM_IO_ERR;
+		goto free_lba_list;
+	}
+
+	/* Read from GC victim block */
+	if (pblk_submit_read_gc(pblk, lba_list, data, nr_secs,
+							&secs_to_gc, line)) {
+		ret = NVM_IO_ERR;
+		goto free_data;
+	}
+
+	if (!secs_to_gc)
+		goto free_data;
+
+	gc_rq = kmalloc(sizeof(struct pblk_gc_rq), GFP_KERNEL);
+	if (!gc_rq) {
+		ret = NVM_IO_ERR;
+		goto free_data;
+	}
+
+	gc_rq->line = line;
+	gc_rq->data = data;
+	gc_rq->lba_list = lba_list;
+	gc_rq->nr_secs = nr_secs;
+	gc_rq->secs_to_gc = secs_to_gc;
+
+	kref_get(&line->ref);
+
+retry:
+	spin_lock(&gc->w_lock);
+	if (gc->w_entries > 256) {
+		spin_unlock(&gc->w_lock);
+		usleep_range(256, 1024);
+		goto retry;
+	}
+	gc->w_entries++;
+	list_add_tail(&gc_rq->list, &gc->w_list);
+	spin_unlock(&gc->w_lock);
+
+	pblk_gc_writer_kick(&pblk->gc);
+
+	return NVM_IO_OK;
+
+free_data:
+	kfree(data);
+free_lba_list:
+	kfree(lba_list);
+
+	return ret;
+}
+
+static void pblk_put_line_back(struct pblk *pblk, struct pblk_line *line)
+{
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
+	struct list_head *move_list;
+
+	spin_lock(&line->lock);
+	WARN_ON(line->state != PBLK_LINESTATE_GC);
+	line->state = PBLK_LINESTATE_CLOSED;
+	move_list = pblk_line_gc_list(pblk, line);
+	spin_unlock(&line->lock);
+
+	if (move_list) {
+		spin_lock(&l_mg->gc_lock);
+		list_add_tail(&line->list, move_list);
+		spin_unlock(&l_mg->gc_lock);
+	}
+}
+
+static void pblk_gc_line_ws(struct work_struct *work)
+{
+	struct pblk_line_ws *line_ws = container_of(work, struct pblk_line_ws,
+									ws);
+	struct pblk *pblk = line_ws->pblk;
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
+	struct pblk_line *line = line_ws->line;
+	struct pblk_line_meta *lm = &pblk->lm;
+	__le64 *lba_list = line_ws->priv;
+	u64 *gc_list;
+	int sec_left;
+	int nr_ppas, bit;
+	int put_line = 1;
+
+	pr_debug("pblk: line '%d' being reclaimed for GC\n", line->id);
+
+	spin_lock(&line->lock);
+	sec_left = line->vsc;
+	if (!sec_left) {
+		/* Lines are erased before being used (l_mg->data_/log_next) */
+		spin_unlock(&line->lock);
+		goto out;
+	}
+	spin_unlock(&line->lock);
+
+	if (sec_left < 0) {
+		pr_err("pblk: corrupted GC line (%d)\n", line->id);
+		put_line = 0;
+		pblk_put_line_back(pblk, line);
+		goto out;
+	}
+
+	bit = -1;
+next_rq:
+	gc_list = kmalloc_array(pblk->max_write_pgs, sizeof(u64), GFP_KERNEL);
+	if (!gc_list) {
+		put_line = 0;
+		pblk_put_line_back(pblk, line);
+		goto out;
+	}
+
+	nr_ppas = 0;
+	do {
+		bit = find_next_zero_bit(line->invalid_bitmap, lm->sec_per_line,
+								bit + 1);
+		if (bit > line->emeta_ssec)
+			break;
+
+		gc_list[nr_ppas++] = le64_to_cpu(lba_list[bit]);
+	} while (nr_ppas < pblk->max_write_pgs);
+
+	if (unlikely(!nr_ppas)) {
+		kfree(gc_list);
+		goto out;
+	}
+
+	if (pblk_gc_move_valid_secs(pblk, line, gc_list, nr_ppas)) {
+		pr_err("pblk: could not GC all sectors: line:%d (%d/%d/%d)\n",
+						line->id, line->vsc,
+						nr_ppas, nr_ppas);
+		put_line = 0;
+		pblk_put_line_back(pblk, line);
+		goto out;
+	}
+
+	sec_left -= nr_ppas;
+	if (sec_left > 0)
+		goto next_rq;
+
+out:
+	pblk_mfree(line->emeta, l_mg->emeta_alloc_type);
+	mempool_free(line_ws, pblk->line_ws_pool);
+	atomic_dec(&pblk->gc.inflight_gc);
+	if (put_line)
+		kref_put(&line->ref, pblk_line_put);
+}
+
+static int pblk_gc_line(struct pblk *pblk, struct pblk_line *line)
+{
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
+	struct pblk_line_meta *lm = &pblk->lm;
+	struct pblk_line_ws *line_ws;
+	__le64 *lba_list;
+	int ret;
+
+	line_ws = mempool_alloc(pblk->line_ws_pool, GFP_KERNEL);
+	line->emeta = pblk_malloc(lm->emeta_len, l_mg->emeta_alloc_type,
+								GFP_KERNEL);
+	if (!line->emeta) {
+		pr_err("pblk: cannot use GC emeta\n");
+		goto fail_free_ws;
+	}
+
+	ret = pblk_line_read_emeta(pblk, line);
+	if (ret) {
+		pr_err("pblk: line %d read emeta failed (%d)\n", line->id, ret);
+		goto fail_free_emeta;
+	}
+
+	/* If this read fails, it means that emeta is corrupted. For now, leave
+	 * the line untouched. TODO: Implement a recovery routine that scans and
+	 * moves all sectors on the line.
+	 */
+	lba_list = pblk_recov_get_lba_list(pblk, line->emeta);
+	if (!lba_list) {
+		pr_err("pblk: could not interpret emeta (line %d)\n", line->id);
+		goto fail_free_emeta;
+	}
+
+	line_ws->pblk = pblk;
+	line_ws->line = line;
+	line_ws->priv = lba_list;
+
+	INIT_WORK(&line_ws->ws, pblk_gc_line_ws);
+	queue_work(pblk->gc.gc_reader_wq, &line_ws->ws);
+
+	return 0;
+
+fail_free_emeta:
+	pblk_mfree(line->emeta, l_mg->emeta_alloc_type);
+fail_free_ws:
+	mempool_free(line_ws, pblk->line_ws_pool);
+	pblk_put_line_back(pblk, line);
+
+	return 1;
+}
+
+static void pblk_gc_lines(struct pblk *pblk, struct list_head *gc_list)
+{
+	struct pblk_line *line, *tline;
+
+	list_for_each_entry_safe(line, tline, gc_list, list) {
+		if (pblk_gc_line(pblk, line))
+			pr_err("pblk: failed to GC line %d\n", line->id);
+		list_del(&line->list);
+	}
+}
+
+/*
+ * Lines with no valid sectors will be returned to the free list immediately. If
+ * GC is activated - either because the free block count is under the determined
+ * threshold, or because it is being forced from user space - only lines with a
+ * high count of invalid sectors will be recycled.
+ */
+static void pblk_gc_run(struct pblk *pblk)
+{
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
+	struct pblk_gc *gc = &pblk->gc;
+	struct pblk_line *line, *tline;
+	unsigned int nr_blocks_free, nr_blocks_need;
+	struct list_head *group_list;
+	int run_gc, gc_group = 0;
+	int prev_gc = 0;
+	int inflight_gc = atomic_read(&gc->inflight_gc);
+	LIST_HEAD(gc_list);
+
+	spin_lock(&l_mg->gc_lock);
+	list_for_each_entry_safe(line, tline, &l_mg->gc_full_list, list) {
+		spin_lock(&line->lock);
+		WARN_ON(line->state != PBLK_LINESTATE_CLOSED);
+		line->state = PBLK_LINESTATE_GC;
+		spin_unlock(&line->lock);
+
+		list_del(&line->list);
+		kref_put(&line->ref, pblk_line_put);
+	}
+	spin_unlock(&l_mg->gc_lock);
+
+	nr_blocks_need = pblk_rl_gc_thrs(&pblk->rl);
+	nr_blocks_free = pblk_rl_nr_free_blks(&pblk->rl);
+	run_gc = (nr_blocks_need > nr_blocks_free || gc->gc_forced);
+
+next_gc_group:
+	group_list = l_mg->gc_lists[gc_group++];
+	spin_lock(&l_mg->gc_lock);
+	while (run_gc && !list_empty(group_list)) {
+		/* No need to queue up more GC lines than we can handle */
+		if (!run_gc || inflight_gc > gc->gc_jobs_active) {
+			spin_unlock(&l_mg->gc_lock);
+			pblk_gc_lines(pblk, &gc_list);
+			return;
+		}
+
+		line = list_first_entry(group_list, struct pblk_line, list);
+		nr_blocks_free += line->blk_in_line;
+
+		spin_lock(&line->lock);
+		WARN_ON(line->state != PBLK_LINESTATE_CLOSED);
+		line->state = PBLK_LINESTATE_GC;
+		list_move_tail(&line->list, &gc_list);
+		atomic_inc(&gc->inflight_gc);
+		inflight_gc++;
+		spin_unlock(&line->lock);
+
+		prev_gc = 1;
+		run_gc = (nr_blocks_need > nr_blocks_free || gc->gc_forced);
+	}
+	spin_unlock(&l_mg->gc_lock);
+
+	pblk_gc_lines(pblk, &gc_list);
+
+	if (!prev_gc && pblk->rl.rb_state > gc_group &&
+						gc_group < PBLK_NR_GC_LISTS)
+		goto next_gc_group;
+}
+
+
+static void pblk_gc_kick(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+
+	wake_up_process(gc->gc_ts);
+	pblk_gc_writer_kick(gc);
+	mod_timer(&gc->gc_timer, jiffies + msecs_to_jiffies(GC_TIME_MSECS));
+}
+
+static void pblk_gc_timer(unsigned long data)
+{
+	struct pblk *pblk = (struct pblk *)data;
+
+	pblk_gc_kick(pblk);
+}
+
+static int pblk_gc_ts(void *data)
+{
+	struct pblk *pblk = data;
+
+	while (!kthread_should_stop()) {
+		pblk_gc_run(pblk);
+		set_current_state(TASK_INTERRUPTIBLE);
+		io_schedule();
+	}
+
+	return 0;
+}
+
+static int pblk_gc_writer_ts(void *data)
+{
+	struct pblk *pblk = data;
+
+	while (!kthread_should_stop()) {
+		if (!pblk_gc_write(pblk))
+			continue;
+		set_current_state(TASK_INTERRUPTIBLE);
+		io_schedule();
+	}
+
+	return 0;
+}
+
+static void pblk_gc_start(struct pblk *pblk)
+{
+	pblk->gc.gc_active = 1;
+
+	pr_debug("pblk: gc start\n");
+}
+
+int pblk_gc_status(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+	int ret;
+
+	spin_lock(&gc->lock);
+	ret = gc->gc_active;
+	spin_unlock(&gc->lock);
+
+	return ret;
+}
+
+static void __pblk_gc_should_start(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+
+	lockdep_assert_held(&gc->lock);
+
+	if (gc->gc_enabled && !gc->gc_active)
+		pblk_gc_start(pblk);
+}
+
+void pblk_gc_should_start(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+
+	spin_lock(&gc->lock);
+	__pblk_gc_should_start(pblk);
+	spin_unlock(&gc->lock);
+}
+
+/*
+ * If flush_wq == 1 then no lock should be held by the caller since
+ * flush_workqueue can sleep
+ */
+static void pblk_gc_stop(struct pblk *pblk, int flush_wq)
+{
+	spin_lock(&pblk->gc.lock);
+	pblk->gc.gc_active = 0;
+	spin_unlock(&pblk->gc.lock);
+
+	pr_debug("pblk: gc stop\n");
+}
+
+void pblk_gc_should_stop(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+
+	if (gc->gc_active && !gc->gc_forced)
+		pblk_gc_stop(pblk, 0);
+}
+
+void pblk_gc_sysfs_state_show(struct pblk *pblk, int *gc_enabled,
+			      int *gc_active)
+{
+	struct pblk_gc *gc = &pblk->gc;
+
+	spin_lock(&gc->lock);
+	*gc_enabled = gc->gc_enabled;
+	*gc_active = gc->gc_active;
+	spin_unlock(&gc->lock);
+}
+
+void pblk_gc_sysfs_force(struct pblk *pblk, int force)
+{
+	struct pblk_gc *gc = &pblk->gc;
+	int rsv = 0;
+
+	spin_lock(&gc->lock);
+	if (force) {
+		gc->gc_enabled = 1;
+		rsv = 64;
+	}
+	pblk_rl_set_gc_rsc(&pblk->rl, rsv);
+	gc->gc_forced = force;
+	__pblk_gc_should_start(pblk);
+	spin_unlock(&gc->lock);
+}
+
+int pblk_gc_init(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+	int ret;
+
+	gc->gc_ts = kthread_create(pblk_gc_ts, pblk, "pblk-gc-ts");
+	if (IS_ERR(gc->gc_ts)) {
+		pr_err("pblk: could not allocate GC main kthread\n");
+		return PTR_ERR(gc->gc_ts);
+	}
+
+	gc->gc_writer_ts = kthread_create(pblk_gc_writer_ts, pblk,
+							"pblk-gc-writer-ts");
+	if (IS_ERR(gc->gc_writer_ts)) {
+		pr_err("pblk: could not allocate GC writer kthread\n");
+		ret = PTR_ERR(gc->gc_writer_ts);
+		goto fail_free_main_kthread;
+	}
+
+	setup_timer(&gc->gc_timer, pblk_gc_timer, (unsigned long)pblk);
+	mod_timer(&gc->gc_timer, jiffies + msecs_to_jiffies(GC_TIME_MSECS));
+
+	gc->gc_active = 0;
+	gc->gc_forced = 0;
+	gc->gc_enabled = 1;
+	gc->gc_jobs_active = 8;
+	gc->w_entries = 0;
+	atomic_set(&gc->inflight_gc, 0);
+
+	gc->gc_reader_wq = alloc_workqueue("pblk-gc-reader-wq",
+			WQ_MEM_RECLAIM | WQ_UNBOUND, gc->gc_jobs_active);
+	if (!gc->gc_reader_wq) {
+		pr_err("pblk: could not allocate GC reader workqueue\n");
+		ret = -ENOMEM;
+		goto fail_free_writer_kthread;
+	}
+
+	spin_lock_init(&gc->lock);
+	spin_lock_init(&gc->w_lock);
+	INIT_LIST_HEAD(&gc->w_list);
+
+	return 0;
+
+fail_free_main_kthread:
+	kthread_stop(gc->gc_ts);
+fail_free_writer_kthread:
+	kthread_stop(gc->gc_writer_ts);
+
+	return ret;
+}
+
+void pblk_gc_exit(struct pblk *pblk)
+{
+	struct pblk_gc *gc = &pblk->gc;
+
+	flush_workqueue(gc->gc_reader_wq);
+
+	del_timer(&gc->gc_timer);
+	pblk_gc_stop(pblk, 1);
+
+	if (gc->gc_ts)
+		kthread_stop(gc->gc_ts);
+
+	if (pblk->gc.gc_reader_wq)
+		destroy_workqueue(pblk->gc.gc_reader_wq);
+
+	if (gc->gc_writer_ts)
+		kthread_stop(gc->gc_writer_ts);
+}