bcache in userspace; userspace fsck

1 files changed, 387 insertions, 0 deletions

diff --git a/libbcache/journal.h b/libbcache/journal.h
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+#ifndef _BCACHE_JOURNAL_H
+#define _BCACHE_JOURNAL_H
+
+/*
+ * THE JOURNAL:
+ *
+ * The primary purpose of the journal is to log updates (insertions) to the
+ * b-tree, to avoid having to do synchronous updates to the b-tree on disk.
+ *
+ * Without the journal, the b-tree is always internally consistent on
+ * disk - and in fact, in the earliest incarnations bcache didn't have a journal
+ * but did handle unclean shutdowns by doing all index updates synchronously
+ * (with coalescing).
+ *
+ * Updates to interior nodes still happen synchronously and without the journal
+ * (for simplicity) - this may change eventually but updates to interior nodes
+ * are rare enough it's not a huge priority.
+ *
+ * This means the journal is relatively separate from the b-tree; it consists of
+ * just a list of keys and journal replay consists of just redoing those
+ * insertions in same order that they appear in the journal.
+ *
+ * PERSISTENCE:
+ *
+ * For synchronous updates (where we're waiting on the index update to hit
+ * disk), the journal entry will be written out immediately (or as soon as
+ * possible, if the write for the previous journal entry was still in flight).
+ *
+ * Synchronous updates are specified by passing a closure (@flush_cl) to
+ * bch_btree_insert() or bch_btree_insert_node(), which then pass that parameter
+ * down to the journalling code. That closure will will wait on the journal
+ * write to complete (via closure_wait()).
+ *
+ * If the index update wasn't synchronous, the journal entry will be
+ * written out after 10 ms have elapsed, by default (the delay_ms field
+ * in struct journal).
+ *
+ * JOURNAL ENTRIES:
+ *
+ * A journal entry is variable size (struct jset), it's got a fixed length
+ * header and then a variable number of struct jset_entry entries.
+ *
+ * Journal entries are identified by monotonically increasing 64 bit sequence
+ * numbers - jset->seq; other places in the code refer to this sequence number.
+ *
+ * A jset_entry entry contains one or more bkeys (which is what gets inserted
+ * into the b-tree). We need a container to indicate which b-tree the key is
+ * for; also, the roots of the various b-trees are stored in jset_entry entries
+ * (one for each b-tree) - this lets us add new b-tree types without changing
+ * the on disk format.
+ *
+ * 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.
+ *
+ * JOURNAL LAYOUT ON DISK:
+ *
+ * The journal is written to a ringbuffer of buckets (which is kept in the
+ * superblock); the individual buckets are not necessarily contiguous on disk
+ * which means that journal entries are not allowed to span buckets, but also
+ * that we can resize the journal at runtime if desired (unimplemented).
+ *
+ * The journal buckets exist in the same pool as all the other buckets that are
+ * managed by the allocator and garbage collection - garbage collection marks
+ * the journal buckets as metadata buckets.
+ *
+ * OPEN/DIRTY JOURNAL ENTRIES:
+ *
+ * Open/dirty journal entries are journal entries that contain b-tree updates
+ * that have not yet been written out to the b-tree on disk. We have to track
+ * which journal entries are dirty, and we also have to avoid wrapping around
+ * the journal and overwriting old but still dirty journal entries with new
+ * journal entries.
+ *
+ * On disk, this is represented with the "last_seq" field of struct jset;
+ * last_seq is the first sequence number that journal replay has to replay.
+ *
+ * To avoid overwriting dirty journal entries on disk, we keep a mapping (in
+ * journal_device->seq) of for each journal bucket, the highest sequence number
+ * any journal entry it contains. Then, by comparing that against last_seq we
+ * can determine whether that journal bucket contains dirty journal entries or
+ * not.
+ *
+ * To track which journal entries are dirty, we maintain a fifo of refcounts
+ * (where each entry corresponds to a specific sequence number) - when a ref
+ * goes to 0, that journal entry is no longer dirty.
+ *
+ * Journalling of index updates is done at the same time as the b-tree itself is
+ * being modified (see btree_insert_key()); when we add the key to the journal
+ * the pending b-tree write takes a ref on the journal entry the key was added
+ * to. If a pending b-tree write would need to take refs on multiple dirty
+ * journal entries, it only keeps the ref on the oldest one (since a newer
+ * journal entry will still be replayed if an older entry was dirty).
+ *
+ * JOURNAL FILLING UP:
+ *
+ * There are two ways the journal could fill up; either we could run out of
+ * space to write to, or we could have too many open journal entries and run out
+ * of room in the fifo of refcounts. Since those refcounts are decremented
+ * without any locking we can't safely resize that fifo, so we handle it the
+ * same way.
+ *
+ * If the journal fills up, we start flushing dirty btree nodes until we can
+ * allocate space for a journal write again - preferentially flushing btree
+ * nodes that are pinning the oldest journal entries first.
+ */
+
+#include <linux/hash.h>
+
+#include "journal_types.h"
+
+static inline struct jset_entry *jset_keys_next(struct jset_entry *j)
+{
+	return (void *) __bkey_idx(j, le16_to_cpu(j->u64s));
+}
+
+/*
+ * Only used for holding the journal entries we read in btree_journal_read()
+ * during cache_registration
+ */
+struct journal_replay {
+	struct list_head	list;
+	struct jset		j;
+};
+
+#define JOURNAL_PIN	((32 * 1024) - 1)
+
+static inline bool journal_pin_active(struct journal_entry_pin *pin)
+{
+	return pin->pin_list != NULL;
+}
+
+void bch_journal_pin_add(struct journal *, struct journal_entry_pin *,
+			 journal_pin_flush_fn);
+void bch_journal_pin_drop(struct journal *, struct journal_entry_pin *);
+void bch_journal_pin_add_if_older(struct journal *,
+				  struct journal_entry_pin *,
+				  struct journal_entry_pin *,
+				  journal_pin_flush_fn);
+
+struct closure;
+struct cache_set;
+struct keylist;
+
+struct bkey_i *bch_journal_find_btree_root(struct cache_set *, struct jset *,
+					   enum btree_id, unsigned *);
+
+int bch_journal_seq_should_ignore(struct cache_set *, u64, struct btree *);
+
+u64 bch_inode_journal_seq(struct journal *, u64);
+
+static inline int journal_state_count(union journal_res_state s, int idx)
+{
+	return idx == 0 ? s.buf0_count : s.buf1_count;
+}
+
+static inline void journal_state_inc(union journal_res_state *s)
+{
+	s->buf0_count += s->idx == 0;
+	s->buf1_count += s->idx == 1;
+}
+
+static inline void bch_journal_set_has_inode(struct journal_buf *buf, u64 inum)
+{
+	set_bit(hash_64(inum, ilog2(sizeof(buf->has_inode) * 8)), buf->has_inode);
+}
+
+/*
+ * Amount of space that will be taken up by some keys in the journal (i.e.
+ * including the jset header)
+ */
+static inline unsigned jset_u64s(unsigned u64s)
+{
+	return u64s + sizeof(struct jset_entry) / sizeof(u64);
+}
+
+static inline void bch_journal_add_entry_at(struct journal_buf *buf,
+					    const void *data, size_t u64s,
+					    unsigned type, enum btree_id id,
+					    unsigned level, unsigned offset)
+{
+	struct jset_entry *entry = bkey_idx(buf->data, offset);
+
+	entry->u64s = cpu_to_le16(u64s);
+	entry->btree_id = id;
+	entry->level = level;
+	entry->flags = 0;
+	SET_JOURNAL_ENTRY_TYPE(entry, type);
+
+	memcpy_u64s(entry->_data, data, u64s);
+}
+
+static inline void bch_journal_add_keys(struct journal *j, struct journal_res *res,
+					enum btree_id id, const struct bkey_i *k)
+{
+	struct journal_buf *buf = &j->buf[res->idx];
+	unsigned actual = jset_u64s(k->k.u64s);
+
+	EBUG_ON(!res->ref);
+	BUG_ON(actual > res->u64s);
+
+	bch_journal_set_has_inode(buf, k->k.p.inode);
+
+	bch_journal_add_entry_at(buf, k, k->k.u64s,
+				 JOURNAL_ENTRY_BTREE_KEYS, id,
+				 0, res->offset);
+
+	res->offset	+= actual;
+	res->u64s	-= actual;
+}
+
+void bch_journal_buf_put_slowpath(struct journal *, bool);
+
+static inline void bch_journal_buf_put(struct journal *j, unsigned idx,
+				       bool need_write_just_set)
+{
+	union journal_res_state s;
+
+	s.v = atomic64_sub_return(((union journal_res_state) {
+				    .buf0_count = idx == 0,
+				    .buf1_count = idx == 1,
+				    }).v, &j->reservations.counter);
+
+	EBUG_ON(s.idx != idx && !s.prev_buf_unwritten);
+
+	/*
+	 * Do not initiate a journal write if the journal is in an error state
+	 * (previous journal entry write may have failed)
+	 */
+	if (s.idx != idx &&
+	    !journal_state_count(s, idx) &&
+	    s.cur_entry_offset != JOURNAL_ENTRY_ERROR_VAL)
+		bch_journal_buf_put_slowpath(j, need_write_just_set);
+}
+
+/*
+ * This function releases the journal write structure so other threads can
+ * then proceed to add their keys as well.
+ */
+static inline void bch_journal_res_put(struct journal *j,
+				       struct journal_res *res)
+{
+	if (!res->ref)
+		return;
+
+	lock_release(&j->res_map, 0, _RET_IP_);
+
+	while (res->u64s) {
+		bch_journal_add_entry_at(&j->buf[res->idx], NULL, 0,
+					 JOURNAL_ENTRY_BTREE_KEYS,
+					 0, 0, res->offset);
+		res->offset	+= jset_u64s(0);
+		res->u64s	-= jset_u64s(0);
+	}
+
+	bch_journal_buf_put(j, res->idx, false);
+
+	res->ref = 0;
+}
+
+int bch_journal_res_get_slowpath(struct journal *, struct journal_res *,
+				 unsigned, unsigned);
+
+static inline int journal_res_get_fast(struct journal *j,
+				       struct journal_res *res,
+				       unsigned u64s_min,
+				       unsigned u64s_max)
+{
+	union journal_res_state old, new;
+	u64 v = atomic64_read(&j->reservations.counter);
+
+	do {
+		old.v = new.v = v;
+
+		/*
+		 * Check if there is still room in the current journal
+		 * entry:
+		 */
+		if (old.cur_entry_offset + u64s_min > j->cur_entry_u64s)
+			return 0;
+
+		res->offset	= old.cur_entry_offset;
+		res->u64s	= min(u64s_max, j->cur_entry_u64s -
+				      old.cur_entry_offset);
+
+		journal_state_inc(&new);
+		new.cur_entry_offset += res->u64s;
+	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
+				       old.v, new.v)) != old.v);
+
+	res->ref = true;
+	res->idx = new.idx;
+	res->seq = le64_to_cpu(j->buf[res->idx].data->seq);
+	return 1;
+}
+
+static inline int bch_journal_res_get(struct journal *j, struct journal_res *res,
+				      unsigned u64s_min, unsigned u64s_max)
+{
+	int ret;
+
+	EBUG_ON(res->ref);
+	EBUG_ON(u64s_max < u64s_min);
+
+	if (journal_res_get_fast(j, res, u64s_min, u64s_max))
+		goto out;
+
+	ret = bch_journal_res_get_slowpath(j, res, u64s_min, u64s_max);
+	if (ret)
+		return ret;
+out:
+	lock_acquire_shared(&j->res_map, 0, 0, NULL, _THIS_IP_);
+	EBUG_ON(!res->ref);
+	return 0;
+}
+
+void bch_journal_wait_on_seq(struct journal *, u64, struct closure *);
+void bch_journal_flush_seq_async(struct journal *, u64, struct closure *);
+void bch_journal_flush_async(struct journal *, struct closure *);
+void bch_journal_meta_async(struct journal *, struct closure *);
+
+int bch_journal_flush_seq(struct journal *, u64);
+int bch_journal_flush(struct journal *);
+int bch_journal_meta(struct journal *);
+
+void bch_journal_halt(struct journal *);
+
+static inline int bch_journal_error(struct journal *j)
+{
+	return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL
+		? -EIO : 0;
+}
+
+static inline bool is_journal_device(struct cache *ca)
+{
+	return ca->mi.state == CACHE_ACTIVE && ca->mi.tier == 0;
+}
+
+static inline bool journal_flushes_device(struct cache *ca)
+{
+	return true;
+}
+
+void bch_journal_start(struct cache_set *);
+void bch_journal_mark(struct cache_set *, struct list_head *);
+void bch_journal_entries_free(struct list_head *);
+int bch_journal_read(struct cache_set *, struct list_head *);
+int bch_journal_replay(struct cache_set *, struct list_head *);
+
+static inline void bch_journal_set_replay_done(struct journal *j)
+{
+	spin_lock(&j->lock);
+	BUG_ON(!test_bit(JOURNAL_STARTED, &j->flags));
+
+	set_bit(JOURNAL_REPLAY_DONE, &j->flags);
+	j->cur_pin_list = &fifo_peek_back(&j->pin);
+	spin_unlock(&j->lock);
+}
+
+void bch_journal_free(struct journal *);
+int bch_journal_alloc(struct journal *, unsigned);
+
+ssize_t bch_journal_print_debug(struct journal *, char *);
+
+int bch_cache_journal_alloc(struct cache *);
+
+static inline __le64 *__journal_buckets(struct cache_sb *sb)
+{
+	return sb->_data + bch_journal_buckets_offset(sb);
+}
+
+static inline u64 journal_bucket(struct cache_sb *sb, unsigned nr)
+{
+	return le64_to_cpu(__journal_buckets(sb)[nr]);
+}
+
+static inline void set_journal_bucket(struct cache_sb *sb, unsigned nr, u64 bucket)
+{
+	__journal_buckets(sb)[nr] = cpu_to_le64(bucket);
+}
+
+int bch_journal_move(struct cache *);
+
+#endif /* _BCACHE_JOURNAL_H */