bcachefs: Persist 64 bit io clocks

Originally, bcachefs - going back to bcache - stored, for each bucket, a
16 bit counter corresponding to how long it had been since the bucket
was read from. But, this required periodically rescaling counters on
every bucket to avoid wraparound. That wasn't an issue in bcache, where
we'd perodically rewrite the per bucket metadata all at once, but in
bcachefs we're trying to avoid having to walk every single bucket.

This patch switches to persisting 64 bit io clocks, corresponding to the
64 bit bucket timestaps introduced in the previous patch with
KEY_TYPE_alloc_v2.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 27 insertions, 33 deletions

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index 61b947313c88..3b082da934fb 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -966,29 +966,25 @@ int bch2_fs_mark_dirty(struct bch_fs *c)
 	return ret;
 }
 
-static void
-entry_init_u64s(struct jset_entry *entry, unsigned u64s)
+static struct jset_entry *jset_entry_init(struct jset_entry **end, size_t size)
 {
-	memset(entry, 0, u64s * sizeof(u64));
+	struct jset_entry *entry = *end;
+	unsigned u64s = DIV_ROUND_UP(size, sizeof(u64));
 
+	memset(entry, 0, u64s * sizeof(u64));
 	/*
 	 * The u64s field counts from the start of data, ignoring the shared
 	 * fields.
 	 */
 	entry->u64s = u64s - 1;
-}
 
-static void
-entry_init_size(struct jset_entry *entry, size_t size)
-{
-	unsigned u64s = DIV_ROUND_UP(size, sizeof(u64));
-	entry_init_u64s(entry, u64s);
+	*end = vstruct_next(*end);
+	return entry;
 }
 
-struct jset_entry *
-bch2_journal_super_entries_add_common(struct bch_fs *c,
-				      struct jset_entry *entry,
-				      u64 journal_seq)
+void bch2_journal_super_entries_add_common(struct bch_fs *c,
+					   struct jset_entry **end,
+					   u64 journal_seq)
 {
 	unsigned i;
 
@@ -1003,59 +999,59 @@ bch2_journal_super_entries_add_common(struct bch_fs *c,
 
 	{
 		struct jset_entry_usage *u =
-			container_of(entry, struct jset_entry_usage, entry);
+			container_of(jset_entry_init(end, sizeof(*u)),
+				     struct jset_entry_usage, entry);
 
-		entry_init_size(entry, sizeof(*u));
 		u->entry.type	= BCH_JSET_ENTRY_usage;
 		u->entry.btree_id = FS_USAGE_INODES;
 		u->v		= cpu_to_le64(c->usage_base->nr_inodes);
-
-		entry = vstruct_next(entry);
 	}
 
 	{
 		struct jset_entry_usage *u =
-			container_of(entry, struct jset_entry_usage, entry);
+			container_of(jset_entry_init(end, sizeof(*u)),
+				     struct jset_entry_usage, entry);
 
-		entry_init_size(entry, sizeof(*u));
 		u->entry.type	= BCH_JSET_ENTRY_usage;
 		u->entry.btree_id = FS_USAGE_KEY_VERSION;
 		u->v		= cpu_to_le64(atomic64_read(&c->key_version));
-
-		entry = vstruct_next(entry);
 	}
 
 	for (i = 0; i < BCH_REPLICAS_MAX; i++) {
 		struct jset_entry_usage *u =
-			container_of(entry, struct jset_entry_usage, entry);
+			container_of(jset_entry_init(end, sizeof(*u)),
+				     struct jset_entry_usage, entry);
 
-		entry_init_size(entry, sizeof(*u));
 		u->entry.type	= BCH_JSET_ENTRY_usage;
 		u->entry.btree_id = FS_USAGE_RESERVED;
 		u->entry.level	= i;
 		u->v		= cpu_to_le64(c->usage_base->persistent_reserved[i]);
-
-		entry = vstruct_next(entry);
 	}
 
 	for (i = 0; i < c->replicas.nr; i++) {
 		struct bch_replicas_entry *e =
 			cpu_replicas_entry(&c->replicas, i);
 		struct jset_entry_data_usage *u =
-			container_of(entry, struct jset_entry_data_usage, entry);
+			container_of(jset_entry_init(end, sizeof(*u) + e->nr_devs),
+				     struct jset_entry_data_usage, entry);
 
-		entry_init_size(entry, sizeof(*u) + e->nr_devs);
 		u->entry.type	= BCH_JSET_ENTRY_data_usage;
 		u->v		= cpu_to_le64(c->usage_base->replicas[i]);
 		unsafe_memcpy(&u->r, e, replicas_entry_bytes(e),
 			      "embedded variable length struct");
-
-		entry = vstruct_next(entry);
 	}
 
 	percpu_up_read(&c->mark_lock);
 
-	return entry;
+	for (i = 0; i < 2; i++) {
+		struct jset_entry_clock *clock =
+			container_of(jset_entry_init(end, sizeof(*clock)),
+				     struct jset_entry_clock, entry);
+
+		clock->entry.type = BCH_JSET_ENTRY_clock;
+		clock->rw	= i;
+		clock->time	= atomic64_read(&c->io_clock[i].now);
+	}
 }
 
 void bch2_fs_mark_clean(struct bch_fs *c)
@@ -1084,15 +1080,13 @@ void bch2_fs_mark_clean(struct bch_fs *c)
 	}
 
 	sb_clean->flags		= 0;
-	sb_clean->read_clock	= cpu_to_le16(c->bucket_clock[READ].hand);
-	sb_clean->write_clock	= cpu_to_le16(c->bucket_clock[WRITE].hand);
 	sb_clean->journal_seq	= cpu_to_le64(journal_cur_seq(&c->journal) - 1);
 
 	/* Trying to catch outstanding bug: */
 	BUG_ON(le64_to_cpu(sb_clean->journal_seq) > S64_MAX);
 
 	entry = sb_clean->start;
-	entry = bch2_journal_super_entries_add_common(c, entry, 0);
+	bch2_journal_super_entries_add_common(c, &entry, 0);
 	entry = bch2_btree_roots_to_journal_entries(c, entry, entry);
 	BUG_ON((void *) entry > vstruct_end(&sb_clean->field));