bcachefs: Accumulate accounting keys in journal replay

Until accounting keys hit the btree, they are deltas, not new versions
of the existing key; this means we have to teach journal replay to
accumulate them.

Additionally, the journal doesn't track precisely which entries have
been flushed to the btree; it only tracks a range of entries that may
possibly still need to be flushed.

That means we need to compare accounting keys against the version in the
btree and only flush updates that are newer.

There's another wrinkle with the write buffer: if the write buffer
starts flushing accounting keys before journal replay has finished
flushing accounting keys, journal replay will see the version number
from the new updates and updates from the journal will be lost.

To avoid this, journal replay has to flush accounting keys first, and
we'll be adding a flag so that write buffer flush knows to hold
accounting keys until then.

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

1 files changed, 21 insertions, 5 deletions

diff --git a/fs/bcachefs/btree_trans_commit.c b/fs/bcachefs/btree_trans_commit.c
index 5e67dcb30f33..05e819174697 100644
--- a/fs/bcachefs/btree_trans_commit.c
+++ b/fs/bcachefs/btree_trans_commit.c
@@ -785,8 +785,15 @@ revert_fs_usage:
 
 static noinline void bch2_drop_overwrites_from_journal(struct btree_trans *trans)
 {
+	/*
+	 * Accounting keys aren't deduped in the journal: we have to compare
+	 * each individual update against what's in the btree to see if it has
+	 * been applied yet, and accounting updates also don't overwrite,
+	 * they're deltas that accumulate.
+	 */
 	trans_for_each_update(trans, i)
-		bch2_journal_key_overwritten(trans->c, i->btree_id, i->level, i->k->k.p);
+		if (i->k->k.type != KEY_TYPE_accounting)
+			bch2_journal_key_overwritten(trans->c, i->btree_id, i->level, i->k->k.p);
 }
 
 static noinline int bch2_trans_commit_bkey_invalid(struct btree_trans *trans,
@@ -993,15 +1000,24 @@ static noinline int
 do_bch2_trans_commit_to_journal_replay(struct btree_trans *trans)
 {
 	struct bch_fs *c = trans->c;
-	int ret = 0;
 
 	trans_for_each_update(trans, i) {
-		ret = bch2_journal_key_insert(c, i->btree_id, i->level, i->k);
+		int ret = bch2_journal_key_insert(c, i->btree_id, i->level, i->k);
 		if (ret)
-			break;
+			return ret;
 	}
 
-	return ret;
+	for (struct jset_entry *i = trans->journal_entries;
+	     i != (void *) ((u64 *) trans->journal_entries + trans->journal_entries_u64s);
+	     i = vstruct_next(i))
+		if (i->type == BCH_JSET_ENTRY_btree_keys ||
+		    i->type == BCH_JSET_ENTRY_write_buffer_keys) {
+			int ret = bch2_journal_key_insert(c, i->btree_id, i->level, i->start);
+			if (ret)
+				return ret;
+		}
+
+	return 0;
 }
 
 int __bch2_trans_commit(struct btree_trans *trans, unsigned flags)