Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 852 insertions, 0 deletions

diff --git a/drivers/lightnvm/pblk-rb.c b/drivers/lightnvm/pblk-rb.c
new file mode 100644
index 000000000..d22c13b55
--- /dev/null
+++ b/drivers/lightnvm/pblk-rb.c
@@ -0,0 +1,852 @@
+/*
+ * Copyright (C) 2016 CNEX Labs
+ * Initial release: Javier Gonzalez <javier@cnexlabs.com>
+ *
+ * Based upon the circular ringbuffer.
+ *
+ * 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-rb.c - pblk's write buffer
+ */
+
+#include <linux/circ_buf.h>
+
+#include "pblk.h"
+
+static DECLARE_RWSEM(pblk_rb_lock);
+
+void pblk_rb_data_free(struct pblk_rb *rb)
+{
+	struct pblk_rb_pages *p, *t;
+
+	down_write(&pblk_rb_lock);
+	list_for_each_entry_safe(p, t, &rb->pages, list) {
+		free_pages((unsigned long)page_address(p->pages), p->order);
+		list_del(&p->list);
+		kfree(p);
+	}
+	up_write(&pblk_rb_lock);
+}
+
+/*
+ * Initialize ring buffer. The data and metadata buffers must be previously
+ * allocated and their size must be a power of two
+ * (Documentation/core-api/circular-buffers.rst)
+ */
+int pblk_rb_init(struct pblk_rb *rb, struct pblk_rb_entry *rb_entry_base,
+		 unsigned int power_size, unsigned int power_seg_sz)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	unsigned int init_entry = 0;
+	unsigned int alloc_order = power_size;
+	unsigned int max_order = MAX_ORDER - 1;
+	unsigned int order, iter;
+
+	down_write(&pblk_rb_lock);
+	rb->entries = rb_entry_base;
+	rb->seg_size = (1 << power_seg_sz);
+	rb->nr_entries = (1 << power_size);
+	rb->mem = rb->subm = rb->sync = rb->l2p_update = 0;
+	rb->flush_point = EMPTY_ENTRY;
+
+	spin_lock_init(&rb->w_lock);
+	spin_lock_init(&rb->s_lock);
+
+	INIT_LIST_HEAD(&rb->pages);
+
+	if (alloc_order >= max_order) {
+		order = max_order;
+		iter = (1 << (alloc_order - max_order));
+	} else {
+		order = alloc_order;
+		iter = 1;
+	}
+
+	do {
+		struct pblk_rb_entry *entry;
+		struct pblk_rb_pages *page_set;
+		void *kaddr;
+		unsigned long set_size;
+		int i;
+
+		page_set = kmalloc(sizeof(struct pblk_rb_pages), GFP_KERNEL);
+		if (!page_set) {
+			up_write(&pblk_rb_lock);
+			return -ENOMEM;
+		}
+
+		page_set->order = order;
+		page_set->pages = alloc_pages(GFP_KERNEL, order);
+		if (!page_set->pages) {
+			kfree(page_set);
+			pblk_rb_data_free(rb);
+			up_write(&pblk_rb_lock);
+			return -ENOMEM;
+		}
+		kaddr = page_address(page_set->pages);
+
+		entry = &rb->entries[init_entry];
+		entry->data = kaddr;
+		entry->cacheline = pblk_cacheline_to_addr(init_entry++);
+		entry->w_ctx.flags = PBLK_WRITABLE_ENTRY;
+
+		set_size = (1 << order);
+		for (i = 1; i < set_size; i++) {
+			entry = &rb->entries[init_entry];
+			entry->cacheline = pblk_cacheline_to_addr(init_entry++);
+			entry->data = kaddr + (i * rb->seg_size);
+			entry->w_ctx.flags = PBLK_WRITABLE_ENTRY;
+			bio_list_init(&entry->w_ctx.bios);
+		}
+
+		list_add_tail(&page_set->list, &rb->pages);
+		iter--;
+	} while (iter > 0);
+	up_write(&pblk_rb_lock);
+
+#ifdef CONFIG_NVM_PBLK_DEBUG
+	atomic_set(&rb->inflight_flush_point, 0);
+#endif
+
+	/*
+	 * Initialize rate-limiter, which controls access to the write buffer
+	 * but user and GC I/O
+	 */
+	pblk_rl_init(&pblk->rl, rb->nr_entries);
+
+	return 0;
+}
+
+/*
+ * pblk_rb_calculate_size -- calculate the size of the write buffer
+ */
+unsigned int pblk_rb_calculate_size(unsigned int nr_entries)
+{
+	/* Alloc a write buffer that can at least fit 128 entries */
+	return (1 << max(get_count_order(nr_entries), 7));
+}
+
+void *pblk_rb_entries_ref(struct pblk_rb *rb)
+{
+	return rb->entries;
+}
+
+static void clean_wctx(struct pblk_w_ctx *w_ctx)
+{
+	int flags;
+
+	flags = READ_ONCE(w_ctx->flags);
+	WARN_ONCE(!(flags & PBLK_SUBMITTED_ENTRY),
+			"pblk: overwriting unsubmitted data\n");
+
+	/* Release flags on context. Protect from writes and reads */
+	smp_store_release(&w_ctx->flags, PBLK_WRITABLE_ENTRY);
+	pblk_ppa_set_empty(&w_ctx->ppa);
+	w_ctx->lba = ADDR_EMPTY;
+}
+
+#define pblk_rb_ring_count(head, tail, size) CIRC_CNT(head, tail, size)
+#define pblk_rb_ring_space(rb, head, tail, size) \
+					(CIRC_SPACE(head, tail, size))
+
+/*
+ * Buffer space is calculated with respect to the back pointer signaling
+ * synchronized entries to the media.
+ */
+static unsigned int pblk_rb_space(struct pblk_rb *rb)
+{
+	unsigned int mem = READ_ONCE(rb->mem);
+	unsigned int sync = READ_ONCE(rb->sync);
+
+	return pblk_rb_ring_space(rb, mem, sync, rb->nr_entries);
+}
+
+/*
+ * Buffer count is calculated with respect to the submission entry signaling the
+ * entries that are available to send to the media
+ */
+unsigned int pblk_rb_read_count(struct pblk_rb *rb)
+{
+	unsigned int mem = READ_ONCE(rb->mem);
+	unsigned int subm = READ_ONCE(rb->subm);
+
+	return pblk_rb_ring_count(mem, subm, rb->nr_entries);
+}
+
+unsigned int pblk_rb_sync_count(struct pblk_rb *rb)
+{
+	unsigned int mem = READ_ONCE(rb->mem);
+	unsigned int sync = READ_ONCE(rb->sync);
+
+	return pblk_rb_ring_count(mem, sync, rb->nr_entries);
+}
+
+unsigned int pblk_rb_read_commit(struct pblk_rb *rb, unsigned int nr_entries)
+{
+	unsigned int subm;
+
+	subm = READ_ONCE(rb->subm);
+	/* Commit read means updating submission pointer */
+	smp_store_release(&rb->subm,
+				(subm + nr_entries) & (rb->nr_entries - 1));
+
+	return subm;
+}
+
+static int __pblk_rb_update_l2p(struct pblk_rb *rb, unsigned int to_update)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	struct pblk_line *line;
+	struct pblk_rb_entry *entry;
+	struct pblk_w_ctx *w_ctx;
+	unsigned int user_io = 0, gc_io = 0;
+	unsigned int i;
+	int flags;
+
+	for (i = 0; i < to_update; i++) {
+		entry = &rb->entries[rb->l2p_update];
+		w_ctx = &entry->w_ctx;
+
+		flags = READ_ONCE(entry->w_ctx.flags);
+		if (flags & PBLK_IOTYPE_USER)
+			user_io++;
+		else if (flags & PBLK_IOTYPE_GC)
+			gc_io++;
+		else
+			WARN(1, "pblk: unknown IO type\n");
+
+		pblk_update_map_dev(pblk, w_ctx->lba, w_ctx->ppa,
+							entry->cacheline);
+
+		line = &pblk->lines[pblk_ppa_to_line(w_ctx->ppa)];
+		kref_put(&line->ref, pblk_line_put);
+		clean_wctx(w_ctx);
+		rb->l2p_update = (rb->l2p_update + 1) & (rb->nr_entries - 1);
+	}
+
+	pblk_rl_out(&pblk->rl, user_io, gc_io);
+
+	return 0;
+}
+
+/*
+ * When we move the l2p_update pointer, we update the l2p table - lookups will
+ * point to the physical address instead of to the cacheline in the write buffer
+ * from this moment on.
+ */
+static int pblk_rb_update_l2p(struct pblk_rb *rb, unsigned int nr_entries,
+			      unsigned int mem, unsigned int sync)
+{
+	unsigned int space, count;
+	int ret = 0;
+
+	lockdep_assert_held(&rb->w_lock);
+
+	/* Update l2p only as buffer entries are being overwritten */
+	space = pblk_rb_ring_space(rb, mem, rb->l2p_update, rb->nr_entries);
+	if (space > nr_entries)
+		goto out;
+
+	count = nr_entries - space;
+	/* l2p_update used exclusively under rb->w_lock */
+	ret = __pblk_rb_update_l2p(rb, count);
+
+out:
+	return ret;
+}
+
+/*
+ * Update the l2p entry for all sectors stored on the write buffer. This means
+ * that all future lookups to the l2p table will point to a device address, not
+ * to the cacheline in the write buffer.
+ */
+void pblk_rb_sync_l2p(struct pblk_rb *rb)
+{
+	unsigned int sync;
+	unsigned int to_update;
+
+	spin_lock(&rb->w_lock);
+
+	/* Protect from reads and writes */
+	sync = smp_load_acquire(&rb->sync);
+
+	to_update = pblk_rb_ring_count(sync, rb->l2p_update, rb->nr_entries);
+	__pblk_rb_update_l2p(rb, to_update);
+
+	spin_unlock(&rb->w_lock);
+}
+
+/*
+ * Write @nr_entries to ring buffer from @data buffer if there is enough space.
+ * Typically, 4KB data chunks coming from a bio will be copied to the ring
+ * buffer, thus the write will fail if not all incoming data can be copied.
+ *
+ */
+static void __pblk_rb_write_entry(struct pblk_rb *rb, void *data,
+				  struct pblk_w_ctx w_ctx,
+				  struct pblk_rb_entry *entry)
+{
+	memcpy(entry->data, data, rb->seg_size);
+
+	entry->w_ctx.lba = w_ctx.lba;
+	entry->w_ctx.ppa = w_ctx.ppa;
+}
+
+void pblk_rb_write_entry_user(struct pblk_rb *rb, void *data,
+			      struct pblk_w_ctx w_ctx, unsigned int ring_pos)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	struct pblk_rb_entry *entry;
+	int flags;
+
+	entry = &rb->entries[ring_pos];
+	flags = READ_ONCE(entry->w_ctx.flags);
+#ifdef CONFIG_NVM_PBLK_DEBUG
+	/* Caller must guarantee that the entry is free */
+	BUG_ON(!(flags & PBLK_WRITABLE_ENTRY));
+#endif
+
+	__pblk_rb_write_entry(rb, data, w_ctx, entry);
+
+	pblk_update_map_cache(pblk, w_ctx.lba, entry->cacheline);
+	flags = w_ctx.flags | PBLK_WRITTEN_DATA;
+
+	/* Release flags on write context. Protect from writes */
+	smp_store_release(&entry->w_ctx.flags, flags);
+}
+
+void pblk_rb_write_entry_gc(struct pblk_rb *rb, void *data,
+			    struct pblk_w_ctx w_ctx, struct pblk_line *line,
+			    u64 paddr, unsigned int ring_pos)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	struct pblk_rb_entry *entry;
+	int flags;
+
+	entry = &rb->entries[ring_pos];
+	flags = READ_ONCE(entry->w_ctx.flags);
+#ifdef CONFIG_NVM_PBLK_DEBUG
+	/* Caller must guarantee that the entry is free */
+	BUG_ON(!(flags & PBLK_WRITABLE_ENTRY));
+#endif
+
+	__pblk_rb_write_entry(rb, data, w_ctx, entry);
+
+	if (!pblk_update_map_gc(pblk, w_ctx.lba, entry->cacheline, line, paddr))
+		entry->w_ctx.lba = ADDR_EMPTY;
+
+	flags = w_ctx.flags | PBLK_WRITTEN_DATA;
+
+	/* Release flags on write context. Protect from writes */
+	smp_store_release(&entry->w_ctx.flags, flags);
+}
+
+static int pblk_rb_flush_point_set(struct pblk_rb *rb, struct bio *bio,
+				   unsigned int pos)
+{
+	struct pblk_rb_entry *entry;
+	unsigned int sync, flush_point;
+
+	pblk_rb_sync_init(rb, NULL);
+	sync = READ_ONCE(rb->sync);
+
+	if (pos == sync) {
+		pblk_rb_sync_end(rb, NULL);
+		return 0;
+	}
+
+#ifdef CONFIG_NVM_PBLK_DEBUG
+	atomic_inc(&rb->inflight_flush_point);
+#endif
+
+	flush_point = (pos == 0) ? (rb->nr_entries - 1) : (pos - 1);
+	entry = &rb->entries[flush_point];
+
+	/* Protect flush points */
+	smp_store_release(&rb->flush_point, flush_point);
+
+	if (bio)
+		bio_list_add(&entry->w_ctx.bios, bio);
+
+	pblk_rb_sync_end(rb, NULL);
+
+	return bio ? 1 : 0;
+}
+
+static int __pblk_rb_may_write(struct pblk_rb *rb, unsigned int nr_entries,
+			       unsigned int *pos)
+{
+	unsigned int mem;
+	unsigned int sync;
+
+	sync = READ_ONCE(rb->sync);
+	mem = READ_ONCE(rb->mem);
+
+	if (pblk_rb_ring_space(rb, mem, sync, rb->nr_entries) < nr_entries)
+		return 0;
+
+	if (pblk_rb_update_l2p(rb, nr_entries, mem, sync))
+		return 0;
+
+	*pos = mem;
+
+	return 1;
+}
+
+static int pblk_rb_may_write(struct pblk_rb *rb, unsigned int nr_entries,
+			     unsigned int *pos)
+{
+	if (!__pblk_rb_may_write(rb, nr_entries, pos))
+		return 0;
+
+	/* Protect from read count */
+	smp_store_release(&rb->mem, (*pos + nr_entries) & (rb->nr_entries - 1));
+	return 1;
+}
+
+void pblk_rb_flush(struct pblk_rb *rb)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	unsigned int mem = READ_ONCE(rb->mem);
+
+	if (pblk_rb_flush_point_set(rb, NULL, mem))
+		return;
+
+	pblk_write_kick(pblk);
+}
+
+static int pblk_rb_may_write_flush(struct pblk_rb *rb, unsigned int nr_entries,
+				   unsigned int *pos, struct bio *bio,
+				   int *io_ret)
+{
+	unsigned int mem;
+
+	if (!__pblk_rb_may_write(rb, nr_entries, pos))
+		return 0;
+
+	mem = (*pos + nr_entries) & (rb->nr_entries - 1);
+	*io_ret = NVM_IO_DONE;
+
+	if (bio->bi_opf & REQ_PREFLUSH) {
+		struct pblk *pblk = container_of(rb, struct pblk, rwb);
+
+		atomic64_inc(&pblk->nr_flush);
+		if (pblk_rb_flush_point_set(&pblk->rwb, bio, mem))
+			*io_ret = NVM_IO_OK;
+	}
+
+	/* Protect from read count */
+	smp_store_release(&rb->mem, mem);
+
+	return 1;
+}
+
+/*
+ * Atomically check that (i) there is space on the write buffer for the
+ * incoming I/O, and (ii) the current I/O type has enough budget in the write
+ * buffer (rate-limiter).
+ */
+int pblk_rb_may_write_user(struct pblk_rb *rb, struct bio *bio,
+			   unsigned int nr_entries, unsigned int *pos)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	int io_ret;
+
+	spin_lock(&rb->w_lock);
+	io_ret = pblk_rl_user_may_insert(&pblk->rl, nr_entries);
+	if (io_ret) {
+		spin_unlock(&rb->w_lock);
+		return io_ret;
+	}
+
+	if (!pblk_rb_may_write_flush(rb, nr_entries, pos, bio, &io_ret)) {
+		spin_unlock(&rb->w_lock);
+		return NVM_IO_REQUEUE;
+	}
+
+	pblk_rl_user_in(&pblk->rl, nr_entries);
+	spin_unlock(&rb->w_lock);
+
+	return io_ret;
+}
+
+/*
+ * Look at pblk_rb_may_write_user comment
+ */
+int pblk_rb_may_write_gc(struct pblk_rb *rb, unsigned int nr_entries,
+			 unsigned int *pos)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+
+	spin_lock(&rb->w_lock);
+	if (!pblk_rl_gc_may_insert(&pblk->rl, nr_entries)) {
+		spin_unlock(&rb->w_lock);
+		return 0;
+	}
+
+	if (!pblk_rb_may_write(rb, nr_entries, pos)) {
+		spin_unlock(&rb->w_lock);
+		return 0;
+	}
+
+	pblk_rl_gc_in(&pblk->rl, nr_entries);
+	spin_unlock(&rb->w_lock);
+
+	return 1;
+}
+
+/*
+ * Read available entries on rb and add them to the given bio. To avoid a memory
+ * copy, a page reference to the write buffer is used to be added to the bio.
+ *
+ * This function is used by the write thread to form the write bio that will
+ * persist data on the write buffer to the media.
+ */
+unsigned int pblk_rb_read_to_bio(struct pblk_rb *rb, struct nvm_rq *rqd,
+				 unsigned int pos, unsigned int nr_entries,
+				 unsigned int count)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	struct request_queue *q = pblk->dev->q;
+	struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);
+	struct bio *bio = rqd->bio;
+	struct pblk_rb_entry *entry;
+	struct page *page;
+	unsigned int pad = 0, to_read = nr_entries;
+	unsigned int i;
+	int flags;
+
+	if (count < nr_entries) {
+		pad = nr_entries - count;
+		to_read = count;
+	}
+
+	c_ctx->sentry = pos;
+	c_ctx->nr_valid = to_read;
+	c_ctx->nr_padded = pad;
+
+	for (i = 0; i < to_read; i++) {
+		entry = &rb->entries[pos];
+
+		/* A write has been allowed into the buffer, but data is still
+		 * being copied to it. It is ok to busy wait.
+		 */
+try:
+		flags = READ_ONCE(entry->w_ctx.flags);
+		if (!(flags & PBLK_WRITTEN_DATA)) {
+			io_schedule();
+			goto try;
+		}
+
+		page = virt_to_page(entry->data);
+		if (!page) {
+			pblk_err(pblk, "could not allocate write bio page\n");
+			flags &= ~PBLK_WRITTEN_DATA;
+			flags |= PBLK_SUBMITTED_ENTRY;
+			/* Release flags on context. Protect from writes */
+			smp_store_release(&entry->w_ctx.flags, flags);
+			return NVM_IO_ERR;
+		}
+
+		if (bio_add_pc_page(q, bio, page, rb->seg_size, 0) !=
+								rb->seg_size) {
+			pblk_err(pblk, "could not add page to write bio\n");
+			flags &= ~PBLK_WRITTEN_DATA;
+			flags |= PBLK_SUBMITTED_ENTRY;
+			/* Release flags on context. Protect from writes */
+			smp_store_release(&entry->w_ctx.flags, flags);
+			return NVM_IO_ERR;
+		}
+
+		flags &= ~PBLK_WRITTEN_DATA;
+		flags |= PBLK_SUBMITTED_ENTRY;
+
+		/* Release flags on context. Protect from writes */
+		smp_store_release(&entry->w_ctx.flags, flags);
+
+		pos = (pos + 1) & (rb->nr_entries - 1);
+	}
+
+	if (pad) {
+		if (pblk_bio_add_pages(pblk, bio, GFP_KERNEL, pad)) {
+			pblk_err(pblk, "could not pad page in write bio\n");
+			return NVM_IO_ERR;
+		}
+
+		if (pad < pblk->min_write_pgs)
+			atomic64_inc(&pblk->pad_dist[pad - 1]);
+		else
+			pblk_warn(pblk, "padding more than min. sectors\n");
+
+		atomic64_add(pad, &pblk->pad_wa);
+	}
+
+#ifdef CONFIG_NVM_PBLK_DEBUG
+	atomic_long_add(pad, &pblk->padded_writes);
+#endif
+
+	return NVM_IO_OK;
+}
+
+/*
+ * Copy to bio only if the lba matches the one on the given cache entry.
+ * Otherwise, it means that the entry has been overwritten, and the bio should
+ * be directed to disk.
+ */
+int pblk_rb_copy_to_bio(struct pblk_rb *rb, struct bio *bio, sector_t lba,
+			struct ppa_addr ppa, int bio_iter, bool advanced_bio)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	struct pblk_rb_entry *entry;
+	struct pblk_w_ctx *w_ctx;
+	struct ppa_addr l2p_ppa;
+	u64 pos = pblk_addr_to_cacheline(ppa);
+	void *data;
+	int flags;
+	int ret = 1;
+
+
+#ifdef CONFIG_NVM_PBLK_DEBUG
+	/* Caller must ensure that the access will not cause an overflow */
+	BUG_ON(pos >= rb->nr_entries);
+#endif
+	entry = &rb->entries[pos];
+	w_ctx = &entry->w_ctx;
+	flags = READ_ONCE(w_ctx->flags);
+
+	spin_lock(&rb->w_lock);
+	spin_lock(&pblk->trans_lock);
+	l2p_ppa = pblk_trans_map_get(pblk, lba);
+	spin_unlock(&pblk->trans_lock);
+
+	/* Check if the entry has been overwritten or is scheduled to be */
+	if (!pblk_ppa_comp(l2p_ppa, ppa) || w_ctx->lba != lba ||
+						flags & PBLK_WRITABLE_ENTRY) {
+		ret = 0;
+		goto out;
+	}
+
+	/* Only advance the bio if it hasn't been advanced already. If advanced,
+	 * this bio is at least a partial bio (i.e., it has partially been
+	 * filled with data from the cache). If part of the data resides on the
+	 * media, we will read later on
+	 */
+	if (unlikely(!advanced_bio))
+		bio_advance(bio, bio_iter * PBLK_EXPOSED_PAGE_SIZE);
+
+	data = bio_data(bio);
+	memcpy(data, entry->data, rb->seg_size);
+
+out:
+	spin_unlock(&rb->w_lock);
+	return ret;
+}
+
+struct pblk_w_ctx *pblk_rb_w_ctx(struct pblk_rb *rb, unsigned int pos)
+{
+	unsigned int entry = pos & (rb->nr_entries - 1);
+
+	return &rb->entries[entry].w_ctx;
+}
+
+unsigned int pblk_rb_sync_init(struct pblk_rb *rb, unsigned long *flags)
+	__acquires(&rb->s_lock)
+{
+	if (flags)
+		spin_lock_irqsave(&rb->s_lock, *flags);
+	else
+		spin_lock_irq(&rb->s_lock);
+
+	return rb->sync;
+}
+
+void pblk_rb_sync_end(struct pblk_rb *rb, unsigned long *flags)
+	__releases(&rb->s_lock)
+{
+	lockdep_assert_held(&rb->s_lock);
+
+	if (flags)
+		spin_unlock_irqrestore(&rb->s_lock, *flags);
+	else
+		spin_unlock_irq(&rb->s_lock);
+}
+
+unsigned int pblk_rb_sync_advance(struct pblk_rb *rb, unsigned int nr_entries)
+{
+	unsigned int sync, flush_point;
+	lockdep_assert_held(&rb->s_lock);
+
+	sync = READ_ONCE(rb->sync);
+	flush_point = READ_ONCE(rb->flush_point);
+
+	if (flush_point != EMPTY_ENTRY) {
+		unsigned int secs_to_flush;
+
+		secs_to_flush = pblk_rb_ring_count(flush_point, sync,
+					rb->nr_entries);
+		if (secs_to_flush < nr_entries) {
+			/* Protect flush points */
+			smp_store_release(&rb->flush_point, EMPTY_ENTRY);
+		}
+	}
+
+	sync = (sync + nr_entries) & (rb->nr_entries - 1);
+
+	/* Protect from counts */
+	smp_store_release(&rb->sync, sync);
+
+	return sync;
+}
+
+/* Calculate how many sectors to submit up to the current flush point. */
+unsigned int pblk_rb_flush_point_count(struct pblk_rb *rb)
+{
+	unsigned int subm, sync, flush_point;
+	unsigned int submitted, to_flush;
+
+	/* Protect flush points */
+	flush_point = smp_load_acquire(&rb->flush_point);
+	if (flush_point == EMPTY_ENTRY)
+		return 0;
+
+	/* Protect syncs */
+	sync = smp_load_acquire(&rb->sync);
+
+	subm = READ_ONCE(rb->subm);
+	submitted = pblk_rb_ring_count(subm, sync, rb->nr_entries);
+
+	/* The sync point itself counts as a sector to sync */
+	to_flush = pblk_rb_ring_count(flush_point, sync, rb->nr_entries) + 1;
+
+	return (submitted < to_flush) ? (to_flush - submitted) : 0;
+}
+
+/*
+ * Scan from the current position of the sync pointer to find the entry that
+ * corresponds to the given ppa. This is necessary since write requests can be
+ * completed out of order. The assumption is that the ppa is close to the sync
+ * pointer thus the search will not take long.
+ *
+ * The caller of this function must guarantee that the sync pointer will no
+ * reach the entry while it is using the metadata associated with it. With this
+ * assumption in mind, there is no need to take the sync lock.
+ */
+struct pblk_rb_entry *pblk_rb_sync_scan_entry(struct pblk_rb *rb,
+					      struct ppa_addr *ppa)
+{
+	unsigned int sync, subm, count;
+	unsigned int i;
+
+	sync = READ_ONCE(rb->sync);
+	subm = READ_ONCE(rb->subm);
+	count = pblk_rb_ring_count(subm, sync, rb->nr_entries);
+
+	for (i = 0; i < count; i++)
+		sync = (sync + 1) & (rb->nr_entries - 1);
+
+	return NULL;
+}
+
+int pblk_rb_tear_down_check(struct pblk_rb *rb)
+{
+	struct pblk_rb_entry *entry;
+	int i;
+	int ret = 0;
+
+	spin_lock(&rb->w_lock);
+	spin_lock_irq(&rb->s_lock);
+
+	if ((rb->mem == rb->subm) && (rb->subm == rb->sync) &&
+				(rb->sync == rb->l2p_update) &&
+				(rb->flush_point == EMPTY_ENTRY)) {
+		goto out;
+	}
+
+	if (!rb->entries) {
+		ret = 1;
+		goto out;
+	}
+
+	for (i = 0; i < rb->nr_entries; i++) {
+		entry = &rb->entries[i];
+
+		if (!entry->data) {
+			ret = 1;
+			goto out;
+		}
+	}
+
+out:
+	spin_unlock_irq(&rb->s_lock);
+	spin_unlock(&rb->w_lock);
+
+	return ret;
+}
+
+unsigned int pblk_rb_wrap_pos(struct pblk_rb *rb, unsigned int pos)
+{
+	return (pos & (rb->nr_entries - 1));
+}
+
+int pblk_rb_pos_oob(struct pblk_rb *rb, u64 pos)
+{
+	return (pos >= rb->nr_entries);
+}
+
+ssize_t pblk_rb_sysfs(struct pblk_rb *rb, char *buf)
+{
+	struct pblk *pblk = container_of(rb, struct pblk, rwb);
+	struct pblk_c_ctx *c;
+	ssize_t offset;
+	int queued_entries = 0;
+
+	spin_lock_irq(&rb->s_lock);
+	list_for_each_entry(c, &pblk->compl_list, list)
+		queued_entries++;
+	spin_unlock_irq(&rb->s_lock);
+
+	if (rb->flush_point != EMPTY_ENTRY)
+		offset = scnprintf(buf, PAGE_SIZE,
+			"%u\t%u\t%u\t%u\t%u\t%u\t%u - %u/%u/%u - %d\n",
+			rb->nr_entries,
+			rb->mem,
+			rb->subm,
+			rb->sync,
+			rb->l2p_update,
+#ifdef CONFIG_NVM_PBLK_DEBUG
+			atomic_read(&rb->inflight_flush_point),
+#else
+			0,
+#endif
+			rb->flush_point,
+			pblk_rb_read_count(rb),
+			pblk_rb_space(rb),
+			pblk_rb_flush_point_count(rb),
+			queued_entries);
+	else
+		offset = scnprintf(buf, PAGE_SIZE,
+			"%u\t%u\t%u\t%u\t%u\t%u\tNULL - %u/%u/%u - %d\n",
+			rb->nr_entries,
+			rb->mem,
+			rb->subm,
+			rb->sync,
+			rb->l2p_update,
+#ifdef CONFIG_NVM_PBLK_DEBUG
+			atomic_read(&rb->inflight_flush_point),
+#else
+			0,
+#endif
+			pblk_rb_read_count(rb),
+			pblk_rb_space(rb),
+			pblk_rb_flush_point_count(rb),
+			queued_entries);
+
+	return offset;
+}