FAQ Search Today's Posts Mark Forums Read
» Video Reviews

» Linux Archive

Linux-archive is a website aiming to archive linux email lists and to make them easily accessible for linux users/developers.


» Sponsor

» Partners

» Sponsor

Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
LinkBack Thread Tools
 
Old 05-10-2012, 03:11 AM
Kent Overstreet
 
Default bcache: Journalling

Signed-off-by: Kent Overstreet <koverstreet@google.com>
---
drivers/block/bcache/journal.c | 722 ++++++++++++++++++++++++++++++++++++++++
drivers/block/bcache/journal.h | 113 +++++++
2 files changed, 835 insertions(+), 0 deletions(-)
create mode 100644 drivers/block/bcache/journal.c
create mode 100644 drivers/block/bcache/journal.h

diff --git a/drivers/block/bcache/journal.c b/drivers/block/bcache/journal.c
new file mode 100644
index 0000000..2e43ab6
--- /dev/null
+++ b/drivers/block/bcache/journal.c
@@ -0,0 +1,722 @@
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+/*
+ * Journal replay/recovery:
+ *
+ * This code is all driven from run_cache_set(); we first read the journal
+ * entries, do some other stuff, then we mark all the keys in the journal
+ * entries (same as garbage collection would), then we replay them - reinserting
+ * them into the cache in precisely the same order as they appear in the
+ * journal.
+ *
+ * We only journal keys that go in leaf nodes, which simplifies things quite a
+ * bit.
+ */
+
+static void journal_read_endio(struct bio *bio, int error)
+{
+ struct closure *cl = bio->bi_private;
+ bio_put(bio);
+ closure_put(cl);
+}
+
+static int journal_read_bucket(struct cache *ca, struct list_head *list,
+ struct btree_op *op, unsigned bucket_index)
+{
+ struct journal_device *ja = &ca->journal;
+ struct bio *bio = &ja->bio;
+
+ struct journal_replay *i;
+ struct jset *j, *data = ca->set->journal.w[0].data;
+ unsigned len, left, offset = 0;
+ int ret = 0;
+ sector_t bucket = bucket_to_sector(ca->set, ca->sb.d[bucket_index]);
+
+ pr_debug("reading %llu", (uint64_t) bucket);
+
+ while (offset < ca->sb.bucket_size) {
+reread: left = ca->sb.bucket_size - offset;
+ len = min_t(unsigned, left, PAGE_SECTORS * 8);
+
+ bio_reset(bio);
+ bio->bi_sector = bucket + offset;
+ bio->bi_bdev = ca->bdev;
+ bio->bi_rw = READ;
+ bio->bi_size = len << 9;
+
+ bio->bi_end_io = journal_read_endio;
+ bio->bi_private = &op->cl;
+ bio_map(bio, data);
+
+ closure_bio_submit(bio, &op->cl, ca->set->bio_split);
+ closure_sync(&op->cl);
+
+ /* This function could be simpler now since we no longer write
+ * journal entries that overlap bucket boundaries; this means
+ * the start of a bucket will always have a valid journal entry
+ * if it has any journal entries at all.
+ */
+
+ j = data;
+ while (len) {
+ struct list_head *where;
+ size_t blocks, bytes = set_bytes(j);
+
+ if (j->magic != jset_magic(ca->set))
+ return ret;
+
+ if (bytes > left << 9)
+ return ret;
+
+ if (bytes > len << 9)
+ goto reread;
+
+ if (j->csum != csum_set(j))
+ return ret;
+
+ blocks = set_blocks(j, ca->set);
+
+ while (!list_empty(list)) {
+ i = list_first_entry(list,
+ struct journal_replay, list);
+ if (i->j.seq >= j->last_seq)
+ break;
+ list_del(&i->list);
+ kfree(i);
+ }
+
+ list_for_each_entry_reverse(i, list, list) {
+ if (j->seq == i->j.seq)
+ goto next_set;
+
+ if (j->seq < i->j.last_seq)
+ goto next_set;
+
+ if (j->seq > i->j.seq) {
+ where = &i->list;
+ goto add;
+ }
+ }
+
+ where = list;
+add:
+ i = kmalloc(offsetof(struct journal_replay, j) +
+ bytes, GFP_KERNEL);
+ if (!i)
+ return -ENOMEM;
+ memcpy(&i->j, j, bytes);
+ list_add(&i->list, where);
+ ret = 1;
+
+ ja->seq[bucket_index] = j->seq;
+next_set:
+ offset += blocks * ca->sb.block_size;
+ len -= blocks * ca->sb.block_size;
+ j = ((void *) j) + blocks * block_bytes(ca);
+ }
+ }
+
+ return ret;
+}
+
+int bcache_journal_read(struct cache_set *c, struct list_head *list,
+ struct btree_op *op)
+{
+#define read_bucket(b)
+ ({
+ int ret = journal_read_bucket(ca, list, op, b);
+ __set_bit(b, bitmap);
+ if (ret < 0)
+ return ret;
+ ret;
+ })
+
+ struct cache *ca;
+
+ for_each_cache(ca, c) {
+ struct journal_device *ja = &ca->journal;
+ unsigned long bitmap[SB_JOURNAL_BUCKETS / BITS_PER_LONG];
+ unsigned l, r, m;
+ uint64_t seq;
+
+ bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
+ pr_debug("%u journal buckets", ca->sb.njournal_buckets);
+
+ /* Read journal buckets ordered by golden ratio hash to quickly
+ * find a sequence of buckets with valid journal entries
+ */
+ for (unsigned i = 0; i < ca->sb.njournal_buckets; i++) {
+ l = (i * 2654435769U) % ca->sb.njournal_buckets;
+
+ if (test_bit(l, bitmap))
+ break;
+
+ if (read_bucket(l))
+ goto bsearch;
+ }
+
+ /* If that fails, check all the buckets we haven't checked
+ * already
+ */
+ pr_debug("falling back to linear search");
+
+ for (l = 0; l < ca->sb.njournal_buckets; l++) {
+ if (test_bit(l, bitmap))
+ continue;
+
+ if (read_bucket(l))
+ goto bsearch;
+ }
+bsearch:
+ /* Binary search */
+ m = r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
+ pr_debug("starting binary search, l %u r %u", l, r);
+
+ while (l + 1 < r) {
+ m = (l + r) >> 1;
+
+ if (read_bucket(m))
+ l = m;
+ else
+ r = m;
+ }
+
+ /* Read buckets in reverse order until we stop finding more
+ * journal entries
+ */
+ pr_debug("finishing up");
+ l = m;
+
+ while (1) {
+ if (!l--)
+ l = ca->sb.njournal_buckets - 1;
+
+ if (l == m)
+ break;
+
+ if (test_bit(l, bitmap))
+ continue;
+
+ if (!read_bucket(l))
+ break;
+ }
+
+ seq = 0;
+
+ for (unsigned i = 0; i < ca->sb.njournal_buckets; i++)
+ if (ja->seq[i] > seq) {
+ seq = ja->seq[i];
+ ja->cur = ja->last = i;
+
+ }
+ }
+
+ c->journal.seq = list_entry(list->prev,
+ struct journal_replay,
+ list)->j.seq;
+
+ return 0;
+#undef read_bucket
+}
+
+void bcache_journal_mark(struct cache_set *c, struct list_head *list)
+{
+ atomic_t p = { 0 };
+ struct journal_replay *i;
+ struct journal *j = &c->journal;
+ uint64_t last = j->seq;
+
+ /*
+ * journal.pin should never fill up - we never write a journal
+ * entry when it would fill up. But if for some reason it does, we
+ * iterate over the list in reverse order so that we can just skip that
+ * refcount instead of bugging.
+ */
+
+ list_for_each_entry_reverse(i, list, list) {
+ BUG_ON(last < i->j.seq);
+ i->pin = NULL;
+
+ while (last-- != i->j.seq)
+ if (fifo_free(&j->pin) > 1) {
+ fifo_push_front(&j->pin, p);
+ atomic_set(&fifo_front(&j->pin), 0);
+ }
+
+ if (fifo_free(&j->pin) > 1) {
+ fifo_push_front(&j->pin, p);
+ i->pin = &fifo_front(&j->pin);
+ atomic_set(i->pin, 1);
+ }
+
+ for (struct bkey *k = i->j.start; k < end(&i->j); k = next(k)) {
+ for (unsigned j = 0; j < KEY_PTRS(k); j++) {
+ struct bucket *g = PTR_BUCKET(c, k, j);
+ atomic_inc(&g->pin);
+
+ if (g->prio == btree_prio &&
+ !ptr_stale(c, k, j))
+ g->prio = initial_prio;
+ }
+
+ __btree_mark_key(c, 0, k);
+ }
+ }
+}
+
+int bcache_journal_replay(struct cache_set *s, struct list_head *list,
+ struct btree_op *op)
+{
+ int ret = 0, keys = 0, entries = 0;
+ struct journal_replay *i =
+ list_entry(list->prev, struct journal_replay, list);
+
+ uint64_t start = i->j.last_seq, end = i->j.seq, n = start;
+
+ list_for_each_entry(i, list, list) {
+ BUG_ON(i->pin && atomic_read(i->pin) != 1);
+
+ if (n != i->j.seq)
+ err_printk("journal entries %llu-%llu "
+ "missing! (replaying %llu-%llu)
",
+ n, i->j.seq - 1, start, end);
+
+ for (struct bkey *k = i->j.start; k < end(&i->j); k = next(k)) {
+ pr_debug("%s", pkey(k));
+ bkey_copy(op->keys.top, k);
+ keylist_push(&op->keys);
+
+ op->journal = i->pin;
+ atomic_inc(op->journal);
+
+ ret = bcache_btree_insert(op, s);
+ if (ret)
+ goto err;
+
+ BUG_ON(!keylist_empty(&op->keys));
+ keys++;
+ }
+
+ if (i->pin)
+ atomic_dec(i->pin);
+ n = i->j.seq + 1;
+ entries++;
+ }
+
+ printk(KERN_INFO "bcache: journal replay done, %i keys in %i "
+ "entries, seq %llu-%llu
", keys, entries, start, end);
+
+ while (!list_empty(list)) {
+ i = list_first_entry(list, struct journal_replay, list);
+ list_del(&i->list);
+ kfree(i);
+ }
+err:
+ closure_sync(&op->cl);
+ return ret;
+}
+
+/* Journalling */
+
+static void btree_flush_write(struct cache_set *c)
+{
+ /*
+ * Try to find the btree node with that references the oldest journal
+ * entry, best is our current candidate and is locked if non NULL:
+ */
+ struct btree *b, *best;
+
+ /*
+ * The root of the btree isn't on the lru list. Normally this is fine
+ * because only leaf nodes can have references to journal entries -
+ * unless the root _is_ a leaf node. So we have to special case that:
+ */
+
+ while (!c->root->level) {
+ best = c->root;
+ rw_lock(true, best, 0);
+
+ if (best == c->root && !best->level)
+ goto found;
+ rw_unlock(true, best);
+ }
+
+ mutex_lock(&c->bucket_lock);
+
+ best = NULL;
+ list_for_each_entry(b, &c->btree_cache, list) {
+ if (!down_write_trylock(&b->lock))
+ continue;
+
+ if (!btree_node_dirty(b) ||
+ !btree_current_write(b)->journal) {
+ rw_unlock(true, b);
+ continue;
+ }
+
+ if (!best)
+ best = b;
+ else if (journal_pin_cmp(c,
+ btree_current_write(best),
+ btree_current_write(b))) {
+ rw_unlock(true, best);
+ best = b;
+ } else
+ rw_unlock(true, b);
+ }
+
+ if (best)
+ goto out;
+
+ /* We can't find the best btree node, just pick the first */
+ list_for_each_entry(b, &c->btree_cache, list)
+ if (!b->level && btree_node_dirty(b)) {
+ best = b;
+ mutex_unlock(&c->bucket_lock);
+ rw_lock(true, best, best->level);
+ goto found;
+ }
+
+out:
+ mutex_unlock(&c->bucket_lock);
+
+ if (!best)
+ return;
+found:
+ if (btree_node_dirty(best))
+ btree_write(best, true, NULL);
+ rw_unlock(true, best);
+}
+
+#define last_seq(j) ((j)->seq - fifo_used(&(j)->pin) + 1)
+
+static void journal_reclaim(struct cache_set *c)
+{
+ struct bkey *k = &c->journal.key;
+ struct cache *ca;
+ uint64_t last_seq;
+ unsigned n = 0;
+ atomic_t p;
+
+ while (!atomic_read(&fifo_front(&c->journal.pin)))
+ fifo_pop(&c->journal.pin, p);
+
+ last_seq = last_seq(&c->journal);
+
+ for_each_cache(ca, c) {
+ struct journal_device *ja = &ca->journal;
+
+ while (ja->last != ja->cur &&
+ ja->seq[ja->last] < last_seq)
+ if (++ja->last == ca->sb.njournal_buckets)
+ ja->last = 0;
+ }
+
+ if (c->journal.blocks_free)
+ return;
+
+ /*
+ * Now we allocate:
+ * XXX: Sort by free journal space
+ */
+
+ for_each_cache(ca, c) {
+ struct journal_device *ja = &ca->journal;
+ unsigned next = (ja->cur + 1) % ca->sb.njournal_buckets;
+
+ if (next == ja->last)
+ continue;
+
+ ja->cur = next;
+ k->ptr[n++] = PTR(0,
+ bucket_to_sector(c, ca->sb.d[ja->cur]),
+ ca->sb.nr_this_dev);
+ }
+
+ k->header = KEY_HEADER(0, 0);
+ SET_KEY_PTRS(k, n);
+
+ if (n)
+ c->journal.blocks_free = c->sb.bucket_size >> c->block_bits;
+
+ if (!journal_full(&c->journal))
+ __closure_wake_up(&c->journal.wait);
+}
+
+void bcache_journal_next(struct journal *j)
+{
+ atomic_t p = { 1 };
+
+ j->cur = (j->cur == j->w)
+ ? &j->w[1]
+ : &j->w[0];
+
+ /*
+ * The fifo_push() needs to happen at the same time as j->seq is
+ * incremented for last_seq() to be calculated correctly
+ */
+ BUG_ON(!fifo_push(&j->pin, p));
+ atomic_set(&fifo_back(&j->pin), 1);
+
+ j->cur->data->seq = ++j->seq;
+ j->cur->need_write = false;
+ j->cur->data->keys = 0;
+
+ if (fifo_full(&j->pin))
+ pr_debug("journal_pin full (%zu)", fifo_used(&j->pin));
+}
+
+static void journal_write_endio(struct bio *bio, int error)
+{
+ struct journal_write *w = bio->bi_private;
+
+ cache_set_err_on(error, w->c, "journal io error");
+
+ bio_put(bio);
+ closure_put(&w->c->journal.io.cl);
+}
+
+static void journal_write(struct closure *);
+
+static void journal_write_done(struct closure *cl)
+{
+ struct journal *j = container_of(cl, struct journal, io.cl);
+ struct cache_set *c = container_of(j, struct cache_set, journal);
+
+ struct journal_write *w = (j->cur == j->w)
+ ? &j->w[1]
+ : &j->w[0];
+
+ __closure_wake_up(&w->wait);
+
+ if (c->journal_delay_ms)
+ closure_sleep(&j->io, msecs_to_jiffies(c->journal_delay_ms));
+
+ continue_at(cl, journal_write, system_wq);
+}
+
+static void journal_write_unlocked(struct closure *cl)
+{
+ struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+ struct cache *ca;
+ struct journal_write *w = c->journal.cur;
+ struct bkey *k = &c->journal.key;
+ unsigned sectors = set_blocks(w->data, c) * c->sb.block_size;
+
+ struct bio *bio;
+ struct bio_list list;
+ bio_list_init(&list);
+
+ if (!w->need_write) {
+ /*
+ * XXX: have to unlock closure before we unlock journal lock,
+ * else we race with bcache_journal(). But this way we race
+ * against cache set unregister. Doh.
+ */
+ set_closure_fn(cl, NULL, NULL);
+ closure_sub(cl, CLOSURE_RUNNING + 1);
+ spin_unlock(&c->journal.lock);
+ return;
+ } else if (journal_full(&c->journal)) {
+ journal_reclaim(c);
+ spin_unlock(&c->journal.lock);
+
+ btree_flush_write(c);
+ continue_at(cl, journal_write, system_wq);
+ }
+
+ c->journal.blocks_free -= set_blocks(w->data, c);
+
+ w->data->btree_level = c->root->level;
+
+ bkey_copy(&w->data->btree_root, &c->root->key);
+ bkey_copy(&w->data->uuid_bucket, &c->uuid_bucket);
+
+ for_each_cache(ca, c)
+ w->data->prio_bucket[ca->sb.nr_this_dev] = ca->prio_buckets[0];
+
+ w->data->magic = jset_magic(c);
+ w->data->version = BCACHE_JSET_VERSION;
+ w->data->last_seq = last_seq(&c->journal);
+ w->data->csum = csum_set(w->data);
+
+ for (unsigned i = 0; i < KEY_PTRS(k); i++) {
+ ca = PTR_CACHE(c, k, i);
+ bio = &ca->journal.bio;
+
+ atomic_long_add(sectors, &ca->meta_sectors_written);
+
+ bio_reset(bio);
+ bio->bi_sector = PTR_OFFSET(k, i);
+ bio->bi_bdev = ca->bdev;
+ bio->bi_rw = REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH;
+ bio->bi_size = sectors << 9;
+
+ bio->bi_end_io = journal_write_endio;
+ bio->bi_private = w;
+ bio_map(bio, w->data);
+
+ trace_bcache_journal_write(bio);
+ bio_list_add(&list, bio);
+
+ SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + sectors);
+
+ ca->journal.seq[ca->journal.cur] = w->data->seq;
+ }
+
+ atomic_dec_bug(&fifo_back(&c->journal.pin));
+ bcache_journal_next(&c->journal);
+ journal_reclaim(c);
+
+ spin_unlock(&c->journal.lock);
+
+ while ((bio = bio_list_pop(&list)))
+ closure_bio_submit(bio, cl, c->bio_split);
+
+ continue_at(cl, journal_write_done, NULL);
+}
+
+static void journal_write(struct closure *cl)
+{
+ struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+
+ spin_lock(&c->journal.lock);
+ journal_write_unlocked(cl);
+}
+
+static void __journal_try_write(struct cache_set *c, bool noflush)
+{
+ struct closure *cl = &c->journal.io.cl;
+
+ if (!closure_trylock(cl, &c->cl))
+ spin_unlock(&c->journal.lock);
+ else if (noflush && journal_full(&c->journal)) {
+ spin_unlock(&c->journal.lock);
+ continue_at(cl, journal_write, system_wq);
+ } else
+ journal_write_unlocked(cl);
+}
+
+#define journal_try_write(c) __journal_try_write(c, false)
+
+void bcache_journal_meta(struct cache_set *c, struct closure *cl)
+{
+ struct journal_write *w;
+
+ if (CACHE_SYNC(&c->sb)) {
+ spin_lock(&c->journal.lock);
+
+ w = c->journal.cur;
+ w->need_write = true;
+
+ if (cl)
+ BUG_ON(!closure_wait(&w->wait, cl));
+
+ __journal_try_write(c, true);
+ }
+}
+
+/*
+ * Entry point to the journalling code - bio_insert() and btree_invalidate()
+ * pass bcache_journal() a list of keys to be journalled, and then
+ * bcache_journal() hands those same keys off to btree_insert_async()
+ */
+
+void bcache_journal(struct closure *cl)
+{
+ struct btree_op *op = container_of(cl, struct btree_op, cl);
+ struct cache_set *c = op->d->c;
+ struct journal_write *w;
+ size_t b, n = ((uint64_t *) op->keys.top) - op->keys.list;
+
+ if (op->type != BTREE_INSERT ||
+ !CACHE_SYNC(&c->sb))
+ goto out;
+
+ /*
+ * If we're looping because we errored, might already be waiting on
+ * another journal write:
+ */
+ while (atomic_read(&cl->parent->remaining) & CLOSURE_WAITING)
+ closure_sync(cl->parent);
+
+ spin_lock(&c->journal.lock);
+
+ if (journal_full(&c->journal)) {
+ /* XXX: tracepoint */
+ closure_wait(&c->journal.wait, cl);
+
+ journal_reclaim(c);
+ spin_unlock(&c->journal.lock);
+
+ btree_flush_write(c);
+ continue_at(cl, bcache_journal, bcache_wq);
+ }
+
+ w = c->journal.cur;
+ w->need_write = true;
+ b = __set_blocks(w->data, w->data->keys + n, c);
+
+ if (b * c->sb.block_size > PAGE_SECTORS << JSET_BITS ||
+ b > c->journal.blocks_free) {
+ /* XXX: If we were inserting so many keys that they won't fit in
+ * an _empty_ journal write, we'll deadlock. For now, handle
+ * this in keylist_realloc() - but something to think about.
+ */
+ BUG_ON(!w->data->keys);
+
+ /* XXX: tracepoint */
+ BUG_ON(!closure_wait(&w->wait, cl));
+
+ closure_flush(&c->journal.io);
+
+ journal_try_write(c);
+ continue_at(cl, bcache_journal, bcache_wq);
+ }
+
+ memcpy(end(w->data), op->keys.list, n * sizeof(uint64_t));
+ w->data->keys += n;
+
+ op->journal = &fifo_back(&c->journal.pin);
+ atomic_inc(op->journal);
+
+ if (op->flush_journal) {
+ closure_flush(&c->journal.io);
+ closure_wait(&w->wait, cl->parent);
+ }
+
+ journal_try_write(c);
+out:
+ bcache_btree_insert_async(cl);
+}
+
+void bcache_journal_free(struct cache_set *c)
+{
+ free_pages((unsigned long) c->journal.w[1].data, JSET_BITS);
+ free_pages((unsigned long) c->journal.w[0].data, JSET_BITS);
+ free_fifo(&c->journal.pin);
+}
+
+int bcache_journal_alloc(struct cache_set *c)
+{
+ struct journal *j = &c->journal;
+
+ closure_init_unlocked(&j->io);
+ spin_lock_init(&j->lock);
+
+ c->journal_delay_ms = 100;
+
+ j->w[0].c = c;
+ j->w[1].c = c;
+
+ if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
+ !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)) ||
+ !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)))
+ return -ENOMEM;
+
+ return 0;
+}
diff --git a/drivers/block/bcache/journal.h b/drivers/block/bcache/journal.h
new file mode 100644
index 0000000..eb829e9
--- /dev/null
+++ b/drivers/block/bcache/journal.h
@@ -0,0 +1,113 @@
+#ifndef _BCACHE_JOURNAL_H
+#define _BCACHE_JOURNAL_H
+
+#define BCACHE_JSET_VERSION_UUIDv1 1
+/* Always latest UUID format */
+#define BCACHE_JSET_VERSION_UUID 1
+#define BCACHE_JSET_VERSION 1
+
+/*
+ * On disk format for a journal entry:
+ * seq is monotonically increasing; every journal entry has its own unique
+ * sequence number.
+ *
+ * last_seq is the oldest journal entry that still has keys the btree hasn't
+ * flushed to disk yet.
+ *
+ * version is for on disk format changes.
+ */
+struct jset {
+ uint64_t csum;
+ uint64_t magic;
+ uint64_t seq;
+ uint32_t version;
+ uint32_t keys;
+
+ uint64_t last_seq;
+
+ BKEY_PADDED(uuid_bucket);
+ BKEY_PADDED(btree_root);
+ uint16_t btree_level;
+ uint16_t pad[3];
+
+ uint64_t prio_bucket[MAX_CACHES_PER_SET];
+
+ union {
+ struct bkey start[0];
+ uint64_t d[0];
+ };
+};
+
+/*
+ * Only used for holding the journal entries we read in btree_journal_read()
+ * during cache_registration
+ */
+struct journal_replay {
+ struct list_head list;
+ atomic_t *pin;
+ struct jset j;
+};
+
+/*
+ * We put two of these in struct journal; we used them for writes to the
+ * journal that are being staged or in flight.
+ */
+struct journal_write {
+ struct jset *data;
+#define JSET_BITS 3
+
+ struct cache_set *c;
+ closure_list_t wait;
+ bool need_write;
+};
+
+struct journal {
+ spinlock_t lock;
+ /* used when waiting because the journal was full */
+ closure_list_t wait;
+ struct closure_with_timer io;
+
+ unsigned blocks_free;
+ uint64_t seq;
+ DECLARE_FIFO(atomic_t, pin);
+
+ BKEY_PADDED(key);
+
+ struct journal_write w[2], *cur;
+};
+
+struct journal_device {
+ unsigned cur;
+ unsigned last;
+ uint64_t seq[SB_JOURNAL_BUCKETS];
+
+ struct bio bio;
+ struct bio_vec bv[8];
+};
+
+#define journal_pin_cmp(c, l, r)
+ (fifo_idx(&(c)->journal.pin, (l)->journal) >
+ fifo_idx(&(c)->journal.pin, (r)->journal))
+
+#define JOURNAL_PIN 20000
+
+#define journal_full(j)
+ (!(j)->blocks_free || fifo_free(&(j)->pin) <= 1)
+
+struct closure;
+struct cache_set;
+struct btree_op;
+
+void bcache_journal(struct closure *);
+void bcache_journal_next(struct journal *);
+void bcache_journal_mark(struct cache_set *, struct list_head *);
+void bcache_journal_meta(struct cache_set *, struct closure *);
+int bcache_journal_read(struct cache_set *, struct list_head *,
+ struct btree_op *);
+int bcache_journal_replay(struct cache_set *, struct list_head *,
+ struct btree_op *);
+
+void bcache_journal_free(struct cache_set *);
+int bcache_journal_alloc(struct cache_set *);
+
+#endif /* _BCACHE_JOURNAL_H */
--
1.7.9.rc2

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
 
Old 07-23-2012, 11:50 PM
Kent Overstreet
 
Default bcache: Journalling

Signed-off-by: Kent Overstreet <koverstreet@google.com>
---
drivers/md/bcache/journal.c | 703 +++++++++++++++++++++++++++++++++++++++++++
drivers/md/bcache/journal.h | 159 ++++++++++
2 files changed, 862 insertions(+), 0 deletions(-)
create mode 100644 drivers/md/bcache/journal.c
create mode 100644 drivers/md/bcache/journal.h

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
new file mode 100644
index 0000000..dd5d9fd
--- /dev/null
+++ b/drivers/md/bcache/journal.c
@@ -0,0 +1,703 @@
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+/*
+ * Journal replay/recovery:
+ *
+ * This code is all driven from run_cache_set(); we first read the journal
+ * entries, do some other stuff, then we mark all the keys in the journal
+ * entries (same as garbage collection would), then we replay them - reinserting
+ * them into the cache in precisely the same order as they appear in the
+ * journal.
+ *
+ * We only journal keys that go in leaf nodes, which simplifies things quite a
+ * bit.
+ */
+
+static void journal_read_endio(struct bio *bio, int error)
+{
+ struct closure *cl = bio->bi_private;
+ closure_put(cl);
+}
+
+static int journal_read_bucket(struct cache *ca, struct list_head *list,
+ struct btree_op *op, unsigned bucket_index)
+{
+ struct journal_device *ja = &ca->journal;
+ struct bio *bio = &ja->bio;
+
+ struct journal_replay *i;
+ struct jset *j, *data = ca->set->journal.w[0].data;
+ unsigned len, left, offset = 0;
+ int ret = 0;
+ sector_t bucket = bucket_to_sector(ca->set, ca->sb.d[bucket_index]);
+
+ pr_debug("reading %llu", (uint64_t) bucket);
+
+ while (offset < ca->sb.bucket_size) {
+reread: left = ca->sb.bucket_size - offset;
+ len = min_t(unsigned, left, PAGE_SECTORS * 8);
+
+ bio_reset(bio);
+ bio->bi_sector = bucket + offset;
+ bio->bi_bdev = ca->bdev;
+ bio->bi_rw = READ;
+ bio->bi_size = len << 9;
+
+ bio->bi_end_io = journal_read_endio;
+ bio->bi_private = &op->cl;
+ bio_map(bio, data);
+
+ closure_bio_submit(bio, &op->cl);
+ closure_sync(&op->cl);
+
+ /* This function could be simpler now since we no longer write
+ * journal entries that overlap bucket boundaries; this means
+ * the start of a bucket will always have a valid journal entry
+ * if it has any journal entries at all.
+ */
+
+ j = data;
+ while (len) {
+ struct list_head *where;
+ size_t blocks, bytes = set_bytes(j);
+
+ if (j->magic != jset_magic(ca->set))
+ return ret;
+
+ if (bytes > left << 9)
+ return ret;
+
+ if (bytes > len << 9)
+ goto reread;
+
+ if (j->csum != csum_set(j))
+ return ret;
+
+ blocks = set_blocks(j, ca->set);
+
+ while (!list_empty(list)) {
+ i = list_first_entry(list,
+ struct journal_replay, list);
+ if (i->j.seq >= j->last_seq)
+ break;
+ list_del(&i->list);
+ kfree(i);
+ }
+
+ list_for_each_entry_reverse(i, list, list) {
+ if (j->seq == i->j.seq)
+ goto next_set;
+
+ if (j->seq < i->j.last_seq)
+ goto next_set;
+
+ if (j->seq > i->j.seq) {
+ where = &i->list;
+ goto add;
+ }
+ }
+
+ where = list;
+add:
+ i = kmalloc(offsetof(struct journal_replay, j) +
+ bytes, GFP_KERNEL);
+ if (!i)
+ return -ENOMEM;
+ memcpy(&i->j, j, bytes);
+ list_add(&i->list, where);
+ ret = 1;
+
+ ja->seq[bucket_index] = j->seq;
+next_set:
+ offset += blocks * ca->sb.block_size;
+ len -= blocks * ca->sb.block_size;
+ j = ((void *) j) + blocks * block_bytes(ca);
+ }
+ }
+
+ return ret;
+}
+
+int bch_journal_read(struct cache_set *c, struct list_head *list,
+ struct btree_op *op)
+{
+#define read_bucket(b)
+ ({
+ int ret = journal_read_bucket(ca, list, op, b);
+ __set_bit(b, bitmap);
+ if (ret < 0)
+ return ret;
+ ret;
+ })
+
+ struct cache *ca;
+
+ for_each_cache(ca, c) {
+ struct journal_device *ja = &ca->journal;
+ unsigned long bitmap[SB_JOURNAL_BUCKETS / BITS_PER_LONG];
+ unsigned l, r, m;
+ uint64_t seq;
+
+ bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
+ pr_debug("%u journal buckets", ca->sb.njournal_buckets);
+
+ /* Read journal buckets ordered by golden ratio hash to quickly
+ * find a sequence of buckets with valid journal entries
+ */
+ for (unsigned i = 0; i < ca->sb.njournal_buckets; i++) {
+ l = (i * 2654435769U) % ca->sb.njournal_buckets;
+
+ if (test_bit(l, bitmap))
+ break;
+
+ if (read_bucket(l))
+ goto bsearch;
+ }
+
+ /* If that fails, check all the buckets we haven't checked
+ * already
+ */
+ pr_debug("falling back to linear search");
+
+ for (l = 0; l < ca->sb.njournal_buckets; l++) {
+ if (test_bit(l, bitmap))
+ continue;
+
+ if (read_bucket(l))
+ goto bsearch;
+ }
+bsearch:
+ /* Binary search */
+ m = r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
+ pr_debug("starting binary search, l %u r %u", l, r);
+
+ while (l + 1 < r) {
+ m = (l + r) >> 1;
+
+ if (read_bucket(m))
+ l = m;
+ else
+ r = m;
+ }
+
+ /* Read buckets in reverse order until we stop finding more
+ * journal entries
+ */
+ pr_debug("finishing up");
+ l = m;
+
+ while (1) {
+ if (!l--)
+ l = ca->sb.njournal_buckets - 1;
+
+ if (l == m)
+ break;
+
+ if (test_bit(l, bitmap))
+ continue;
+
+ if (!read_bucket(l))
+ break;
+ }
+
+ seq = 0;
+
+ for (unsigned i = 0; i < ca->sb.njournal_buckets; i++)
+ if (ja->seq[i] > seq) {
+ seq = ja->seq[i];
+ ja->cur = ja->last = i;
+
+ }
+ }
+
+ c->journal.seq = list_entry(list->prev,
+ struct journal_replay,
+ list)->j.seq;
+
+ return 0;
+#undef read_bucket
+}
+
+void bch_journal_mark(struct cache_set *c, struct list_head *list)
+{
+ atomic_t p = { 0 };
+ struct journal_replay *i;
+ struct journal *j = &c->journal;
+ uint64_t last = j->seq;
+
+ /*
+ * journal.pin should never fill up - we never write a journal
+ * entry when it would fill up. But if for some reason it does, we
+ * iterate over the list in reverse order so that we can just skip that
+ * refcount instead of bugging.
+ */
+
+ list_for_each_entry_reverse(i, list, list) {
+ BUG_ON(last < i->j.seq);
+ i->pin = NULL;
+
+ while (last-- != i->j.seq)
+ if (fifo_free(&j->pin) > 1) {
+ fifo_push_front(&j->pin, p);
+ atomic_set(&fifo_front(&j->pin), 0);
+ }
+
+ if (fifo_free(&j->pin) > 1) {
+ fifo_push_front(&j->pin, p);
+ i->pin = &fifo_front(&j->pin);
+ atomic_set(i->pin, 1);
+ }
+
+ for (struct bkey *k = i->j.start;
+ k < end(&i->j);
+ k = bkey_next(k)) {
+ for (unsigned j = 0; j < KEY_PTRS(k); j++) {
+ struct bucket *g = PTR_BUCKET(c, k, j);
+ atomic_inc(&g->pin);
+
+ if (g->prio == BTREE_PRIO &&
+ !ptr_stale(c, k, j))
+ g->prio = INITIAL_PRIO;
+ }
+
+ __bch_btree_mark_key(c, 0, k);
+ }
+ }
+}
+
+int bch_journal_replay(struct cache_set *s, struct list_head *list,
+ struct btree_op *op)
+{
+ int ret = 0, keys = 0, entries = 0;
+ struct journal_replay *i =
+ list_entry(list->prev, struct journal_replay, list);
+
+ uint64_t start = i->j.last_seq, end = i->j.seq, n = start;
+
+ list_for_each_entry(i, list, list) {
+ BUG_ON(i->pin && atomic_read(i->pin) != 1);
+
+ if (n != i->j.seq)
+ err_printk("journal entries %llu-%llu "
+ "missing! (replaying %llu-%llu)
",
+ n, i->j.seq - 1, start, end);
+
+ for (struct bkey *k = i->j.start;
+ k < end(&i->j);
+ k = bkey_next(k)) {
+ pr_debug("%s", pkey(k));
+ bkey_copy(op->keys.top, k);
+ bch_keylist_push(&op->keys);
+
+ op->journal = i->pin;
+ atomic_inc(op->journal);
+
+ ret = bch_btree_insert(op, s);
+ if (ret)
+ goto err;
+
+ BUG_ON(!bch_keylist_empty(&op->keys));
+ keys++;
+ }
+
+ if (i->pin)
+ atomic_dec(i->pin);
+ n = i->j.seq + 1;
+ entries++;
+ }
+
+ printk(KERN_INFO "bcache: journal replay done, %i keys in %i "
+ "entries, seq %llu-%llu
", keys, entries, start, end);
+
+ while (!list_empty(list)) {
+ i = list_first_entry(list, struct journal_replay, list);
+ list_del(&i->list);
+ kfree(i);
+ }
+err:
+ closure_sync(&op->cl);
+ return ret;
+}
+
+/* Journalling */
+
+static void btree_flush_write(struct cache_set *c)
+{
+ /*
+ * Try to find the btree node with that references the oldest journal
+ * entry, best is our current candidate and is locked if non NULL:
+ */
+ struct btree *b, *best = NULL;
+ struct hlist_node *cursor;
+
+ for_each_cached_btree(b, cursor, c) {
+ if (!down_write_trylock(&b->lock))
+ continue;
+
+ if (!btree_node_dirty(b) ||
+ !btree_current_write(b)->journal) {
+ rw_unlock(true, b);
+ continue;
+ }
+
+ if (!best)
+ best = b;
+ else if (journal_pin_cmp(c,
+ btree_current_write(best),
+ btree_current_write(b))) {
+ rw_unlock(true, best);
+ best = b;
+ } else
+ rw_unlock(true, b);
+ }
+
+ if (best)
+ goto out;
+
+ /* We can't find the best btree node, just pick the first */
+ list_for_each_entry(b, &c->btree_cache, list)
+ if (!b->level && btree_node_dirty(b)) {
+ best = b;
+ rw_lock(true, best, best->level);
+ goto found;
+ }
+
+out:
+ if (!best)
+ return;
+found:
+ if (btree_node_dirty(best))
+ bch_btree_write(best, true, NULL);
+ rw_unlock(true, best);
+}
+
+#define last_seq(j) ((j)->seq - fifo_used(&(j)->pin) + 1)
+
+static void journal_reclaim(struct cache_set *c)
+{
+ struct bkey *k = &c->journal.key;
+ struct cache *ca;
+ uint64_t last_seq;
+ unsigned n = 0;
+ atomic_t p;
+
+ while (!atomic_read(&fifo_front(&c->journal.pin)))
+ fifo_pop(&c->journal.pin, p);
+
+ last_seq = last_seq(&c->journal);
+
+ for_each_cache(ca, c) {
+ struct journal_device *ja = &ca->journal;
+
+ while (ja->last != ja->cur &&
+ ja->seq[ja->last] < last_seq)
+ if (++ja->last == ca->sb.njournal_buckets)
+ ja->last = 0;
+ }
+
+ if (c->journal.blocks_free)
+ return;
+
+ /*
+ * Now we allocate:
+ * XXX: Sort by free journal space
+ */
+
+ for_each_cache(ca, c) {
+ struct journal_device *ja = &ca->journal;
+ unsigned next = (ja->cur + 1) % ca->sb.njournal_buckets;
+
+ if (next == ja->last)
+ continue;
+
+ ja->cur = next;
+ k->ptr[n++] = PTR(0,
+ bucket_to_sector(c, ca->sb.d[ja->cur]),
+ ca->sb.nr_this_dev);
+ }
+
+ bkey_init(k);
+ SET_KEY_PTRS(k, n);
+
+ if (n)
+ c->journal.blocks_free = c->sb.bucket_size >> c->block_bits;
+
+ if (!journal_full(&c->journal))
+ __closure_wake_up(&c->journal.wait);
+}
+
+void bch_journal_next(struct journal *j)
+{
+ atomic_t p = { 1 };
+
+ j->cur = (j->cur == j->w)
+ ? &j->w[1]
+ : &j->w[0];
+
+ /*
+ * The fifo_push() needs to happen at the same time as j->seq is
+ * incremented for last_seq() to be calculated correctly
+ */
+ BUG_ON(!fifo_push(&j->pin, p));
+ atomic_set(&fifo_back(&j->pin), 1);
+
+ j->cur->data->seq = ++j->seq;
+ j->cur->need_write = false;
+ j->cur->data->keys = 0;
+
+ if (fifo_full(&j->pin))
+ pr_debug("journal_pin full (%zu)", fifo_used(&j->pin));
+}
+
+static void journal_write_endio(struct bio *bio, int error)
+{
+ struct journal_write *w = bio->bi_private;
+
+ cache_set_err_on(error, w->c, "journal io error");
+ closure_put(&w->c->journal.io.cl);
+}
+
+static void journal_write(struct closure *);
+
+static void journal_write_done(struct closure *cl)
+{
+ struct journal *j = container_of(cl, struct journal, io.cl);
+ struct cache_set *c = container_of(j, struct cache_set, journal);
+
+ struct journal_write *w = (j->cur == j->w)
+ ? &j->w[1]
+ : &j->w[0];
+
+ __closure_wake_up(&w->wait);
+
+ if (c->journal_delay_ms)
+ closure_delay(&j->io, msecs_to_jiffies(c->journal_delay_ms));
+
+ continue_at(cl, journal_write, system_wq);
+}
+
+static void journal_write_unlocked(struct closure *cl)
+{
+ struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+ struct cache *ca;
+ struct journal_write *w = c->journal.cur;
+ struct bkey *k = &c->journal.key;
+ unsigned sectors = set_blocks(w->data, c) * c->sb.block_size;
+
+ struct bio *bio;
+ struct bio_list list;
+ bio_list_init(&list);
+
+ if (!w->need_write) {
+ /*
+ * XXX: have to unlock closure before we unlock journal lock,
+ * else we race with bch_journal(). But this way we race
+ * against cache set unregister. Doh.
+ */
+ set_closure_fn(cl, NULL, NULL);
+ closure_sub(cl, CLOSURE_RUNNING + 1);
+ spin_unlock(&c->journal.lock);
+ return;
+ } else if (journal_full(&c->journal)) {
+ journal_reclaim(c);
+ spin_unlock(&c->journal.lock);
+
+ btree_flush_write(c);
+ continue_at(cl, journal_write, system_wq);
+ }
+
+ c->journal.blocks_free -= set_blocks(w->data, c);
+
+ w->data->btree_level = c->root->level;
+
+ bkey_copy(&w->data->btree_root, &c->root->key);
+ bkey_copy(&w->data->uuid_bucket, &c->uuid_bucket);
+
+ for_each_cache(ca, c)
+ w->data->prio_bucket[ca->sb.nr_this_dev] = ca->prio_buckets[0];
+
+ w->data->magic = jset_magic(c);
+ w->data->version = BCACHE_JSET_VERSION;
+ w->data->last_seq = last_seq(&c->journal);
+ w->data->csum = csum_set(w->data);
+
+ for (unsigned i = 0; i < KEY_PTRS(k); i++) {
+ ca = PTR_CACHE(c, k, i);
+ bio = &ca->journal.bio;
+
+ atomic_long_add(sectors, &ca->meta_sectors_written);
+
+ bio_reset(bio);
+ bio->bi_sector = PTR_OFFSET(k, i);
+ bio->bi_bdev = ca->bdev;
+ bio->bi_rw = REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH;
+ bio->bi_size = sectors << 9;
+
+ bio->bi_end_io = journal_write_endio;
+ bio->bi_private = w;
+ bio_map(bio, w->data);
+
+ trace_bcache_journal_write(bio);
+ bio_list_add(&list, bio);
+
+ SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + sectors);
+
+ ca->journal.seq[ca->journal.cur] = w->data->seq;
+ }
+
+ atomic_dec_bug(&fifo_back(&c->journal.pin));
+ bch_journal_next(&c->journal);
+ journal_reclaim(c);
+
+ spin_unlock(&c->journal.lock);
+
+ while ((bio = bio_list_pop(&list)))
+ closure_bio_submit(bio, cl);
+
+ continue_at(cl, journal_write_done, NULL);
+}
+
+static void journal_write(struct closure *cl)
+{
+ struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+
+ spin_lock(&c->journal.lock);
+ journal_write_unlocked(cl);
+}
+
+static void __journal_try_write(struct cache_set *c, bool noflush)
+{
+ struct closure *cl = &c->journal.io.cl;
+
+ if (!closure_trylock(cl, &c->cl))
+ spin_unlock(&c->journal.lock);
+ else if (noflush && journal_full(&c->journal)) {
+ spin_unlock(&c->journal.lock);
+ continue_at(cl, journal_write, system_wq);
+ } else
+ journal_write_unlocked(cl);
+}
+
+#define journal_try_write(c) __journal_try_write(c, false)
+
+void bch_journal_meta(struct cache_set *c, struct closure *cl)
+{
+ struct journal_write *w;
+
+ if (CACHE_SYNC(&c->sb)) {
+ spin_lock(&c->journal.lock);
+
+ w = c->journal.cur;
+ w->need_write = true;
+
+ if (cl)
+ BUG_ON(!closure_wait(&w->wait, cl));
+
+ __journal_try_write(c, true);
+ }
+}
+
+/*
+ * Entry point to the journalling code - bio_insert() and btree_invalidate()
+ * pass bch_journal() a list of keys to be journalled, and then
+ * bch_journal() hands those same keys off to btree_insert_async()
+ */
+
+void bch_journal(struct closure *cl)
+{
+ struct btree_op *op = container_of(cl, struct btree_op, cl);
+ struct cache_set *c = op->c;
+ struct journal_write *w;
+ size_t b, n = ((uint64_t *) op->keys.top) - op->keys.list;
+
+ if (op->type != BTREE_INSERT ||
+ !CACHE_SYNC(&c->sb))
+ goto out;
+
+ /*
+ * If we're looping because we errored, might already be waiting on
+ * another journal write:
+ */
+ while (atomic_read(&cl->parent->remaining) & CLOSURE_WAITING)
+ closure_sync(cl->parent);
+
+ spin_lock(&c->journal.lock);
+
+ if (journal_full(&c->journal)) {
+ /* XXX: tracepoint */
+ closure_wait(&c->journal.wait, cl);
+
+ journal_reclaim(c);
+ spin_unlock(&c->journal.lock);
+
+ btree_flush_write(c);
+ continue_at(cl, bch_journal, bcache_wq);
+ }
+
+ w = c->journal.cur;
+ w->need_write = true;
+ b = __set_blocks(w->data, w->data->keys + n, c);
+
+ if (b * c->sb.block_size > PAGE_SECTORS << JSET_BITS ||
+ b > c->journal.blocks_free) {
+ /* XXX: If we were inserting so many keys that they won't fit in
+ * an _empty_ journal write, we'll deadlock. For now, handle
+ * this in bch_keylist_realloc() - but something to think about.
+ */
+ BUG_ON(!w->data->keys);
+
+ /* XXX: tracepoint */
+ BUG_ON(!closure_wait(&w->wait, cl));
+
+ closure_flush(&c->journal.io);
+
+ journal_try_write(c);
+ continue_at(cl, bch_journal, bcache_wq);
+ }
+
+ memcpy(end(w->data), op->keys.list, n * sizeof(uint64_t));
+ w->data->keys += n;
+
+ op->journal = &fifo_back(&c->journal.pin);
+ atomic_inc(op->journal);
+
+ if (op->flush_journal) {
+ closure_flush(&c->journal.io);
+ closure_wait(&w->wait, cl->parent);
+ }
+
+ journal_try_write(c);
+out:
+ bch_btree_insert_async(cl);
+}
+
+void bch_journal_free(struct cache_set *c)
+{
+ free_pages((unsigned long) c->journal.w[1].data, JSET_BITS);
+ free_pages((unsigned long) c->journal.w[0].data, JSET_BITS);
+ free_fifo(&c->journal.pin);
+}
+
+int bch_journal_alloc(struct cache_set *c)
+{
+ struct journal *j = &c->journal;
+
+ closure_init_unlocked(&j->io);
+ spin_lock_init(&j->lock);
+
+ c->journal_delay_ms = 100;
+
+ j->w[0].c = c;
+ j->w[1].c = c;
+
+ if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
+ !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)) ||
+ !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)))
+ return -ENOMEM;
+
+ return 0;
+}
diff --git a/drivers/md/bcache/journal.h b/drivers/md/bcache/journal.h
new file mode 100644
index 0000000..0b81ff0
--- /dev/null
+++ b/drivers/md/bcache/journal.h
@@ -0,0 +1,159 @@
+#ifndef _BCACHE_JOURNAL_H
+#define _BCACHE_JOURNAL_H
+
+/*
+ * THE JOURNAL:
+ *
+ * The journal is treated as a circular buffer of buckets - a journal entry
+ * never spans two buckets. This means (not implemented yet) we can resize the
+ * journal at runtime, and will be needed for bcache on raw flash support.
+ *
+ * Journal entries contain a list of keys, ordered by the time they were
+ * inserted; thus journal replay just has to reinsert the keys.
+ *
+ * We also keep some things in the journal header that are logically part of the
+ * superblock - all the things that are frequently updated. This is for future
+ * bcache on raw flash support; the superblock (which will become another
+ * journal) can't be moved or wear leveled, so it contains just enough
+ * information to find the main journal, and the superblock only has to be
+ * rewritten when we want to move/wear level the main journal.
+ *
+ * Currently, we don't journal BTREE_REPLACE operations - this will hopefully be
+ * fixed eventually. This isn't a bug - BTREE_REPLACE is used for insertions
+ * from cache misses, which don't have to be journaled, and for writeback and
+ * moving gc we work around it by flushing the btree to disk before updating the
+ * gc information. But it is a potential issue with incremental garbage
+ * collection, and it's fragile.
+ *
+ * OPEN JOURNAL ENTRIES:
+ *
+ * Each journal entry contains, in the header, the sequence number of the last
+ * journal entry still open - i.e. that has keys that haven't been flushed to
+ * disk in the btree.
+ *
+ * We track this by maintaining a refcount for every open journal entry, in a
+ * fifo; the size of the fifo tells us the number of open journal entries, and
+ * when the atomic_t at the end of the fifo goes to 0 we can pop it off.
+ *
+ * We take a refcount on a journal entry when we add some keys to a journal
+ * entry that we're going to insert (held by struct btree_op), and then when we
+ * insert those keys into the btree the btree write we're setting up takes a
+ * copy of that refcount (held by struct btree_write). That refcount is dropped
+ * when the btree write completes.
+ *
+ * A struct btree_write can only hold a refcount on a single journal entry, but
+ * might contain keys for many journal entries - we handle this by making sure
+ * it always has a refcount on the _oldest_ journal entry of all the journal
+ * entries it has keys for.
+ */
+
+#define BCACHE_JSET_VERSION_UUIDv1 1
+/* Always latest UUID format */
+#define BCACHE_JSET_VERSION_UUID 1
+#define BCACHE_JSET_VERSION 1
+
+/*
+ * On disk format for a journal entry:
+ * seq is monotonically increasing; every journal entry has its own unique
+ * sequence number.
+ *
+ * last_seq is the oldest journal entry that still has keys the btree hasn't
+ * flushed to disk yet.
+ *
+ * version is for on disk format changes.
+ */
+struct jset {
+ uint64_t csum;
+ uint64_t magic;
+ uint64_t seq;
+ uint32_t version;
+ uint32_t keys;
+
+ uint64_t last_seq;
+
+ BKEY_PADDED(uuid_bucket);
+ BKEY_PADDED(btree_root);
+ uint16_t btree_level;
+ uint16_t pad[3];
+
+ uint64_t prio_bucket[MAX_CACHES_PER_SET];
+
+ union {
+ struct bkey start[0];
+ uint64_t d[0];
+ };
+};
+
+/*
+ * Only used for holding the journal entries we read in btree_journal_read()
+ * during cache_registration
+ */
+struct journal_replay {
+ struct list_head list;
+ atomic_t *pin;
+ struct jset j;
+};
+
+/*
+ * We put two of these in struct journal; we used them for writes to the
+ * journal that are being staged or in flight.
+ */
+struct journal_write {
+ struct jset *data;
+#define JSET_BITS 3
+
+ struct cache_set *c;
+ struct closure_waitlist wait;
+ bool need_write;
+};
+
+struct journal {
+ spinlock_t lock;
+ /* used when waiting because the journal was full */
+ struct closure_waitlist wait;
+ struct closure_with_timer io;
+
+ unsigned blocks_free;
+ uint64_t seq;
+ DECLARE_FIFO(atomic_t, pin);
+
+ BKEY_PADDED(key);
+
+ struct journal_write w[2], *cur;
+};
+
+struct journal_device {
+ unsigned cur;
+ unsigned last;
+ uint64_t seq[SB_JOURNAL_BUCKETS];
+
+ struct bio bio;
+ struct bio_vec bv[8];
+};
+
+#define journal_pin_cmp(c, l, r)
+ (fifo_idx(&(c)->journal.pin, (l)->journal) >
+ fifo_idx(&(c)->journal.pin, (r)->journal))
+
+#define JOURNAL_PIN 20000
+
+#define journal_full(j)
+ (!(j)->blocks_free || fifo_free(&(j)->pin) <= 1)
+
+struct closure;
+struct cache_set;
+struct btree_op;
+
+void bch_journal(struct closure *);
+void bch_journal_next(struct journal *);
+void bch_journal_mark(struct cache_set *, struct list_head *);
+void bch_journal_meta(struct cache_set *, struct closure *);
+int bch_journal_read(struct cache_set *, struct list_head *,
+ struct btree_op *);
+int bch_journal_replay(struct cache_set *, struct list_head *,
+ struct btree_op *);
+
+void bch_journal_free(struct cache_set *);
+int bch_journal_alloc(struct cache_set *);
+
+#endif /* _BCACHE_JOURNAL_H */
--
1.7.7.3

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
 

Thread Tools




All times are GMT. The time now is 08:28 AM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.
Copyright 2007 - 2008, www.linux-archive.org