bcachefs: Trust in memory bucket mark

This fixes a bug in the journal replay -> extent_replay_key ->
split_compressed path, when we do an update that changes alloc info but
the alloc info in the btree isn't up to date yet.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_background.c

@@ -205,20 +205,6 @@ void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c,
 			       get_alloc_field(a.v, &d, i));
 }
 
-static inline struct bkey_alloc_unpacked
-alloc_mem_to_key(struct bucket *g, struct bucket_mark m)
-{
-	return (struct bkey_alloc_unpacked) {
-		.gen		= m.gen,
-		.oldest_gen	= g->oldest_gen,
-		.data_type	= m.data_type,
-		.dirty_sectors	= m.dirty_sectors,
-		.cached_sectors	= m.cached_sectors,
-		.read_time	= g->io_time[READ],
-		.write_time	= g->io_time[WRITE],
-	};
-}
-
 int bch2_alloc_read(struct bch_fs *c, struct journal_keys *journal_keys)
 {
 	struct btree_trans trans;

fs/bcachefs/alloc_background.h

@@ -17,6 +17,20 @@ struct bkey_alloc_unpacked bch2_alloc_unpack(struct bkey_s_c);
 void bch2_alloc_pack(struct bkey_i_alloc *,
 		     const struct bkey_alloc_unpacked);
 
+static inline struct bkey_alloc_unpacked
+alloc_mem_to_key(struct bucket *g, struct bucket_mark m)
+{
+	return (struct bkey_alloc_unpacked) {
+		.gen		= m.gen,
+		.oldest_gen	= g->oldest_gen,
+		.data_type	= m.data_type,
+		.dirty_sectors	= m.dirty_sectors,
+		.cached_sectors	= m.cached_sectors,
+		.read_time	= g->io_time[READ],
+		.write_time	= g->io_time[WRITE],
+	};
+}
+
 #define ALLOC_SCAN_BATCH(ca)		max_t(size_t, 1, (ca)->mi.nbuckets >> 9)
 
 const char *bch2_alloc_invalid(const struct bch_fs *, struct bkey_s_c);

fs/bcachefs/buckets.c

@@ -1361,7 +1361,7 @@ static int trans_get_key(struct btree_trans *trans,
 		     : !bkey_cmp(pos, i->iter->pos))) {
 			*iter	= i->iter;
 			*k	= bkey_i_to_s_c(i->k);
-			return 0;
+			return 1;
 		}
 
 	*iter = __bch2_trans_get_iter(trans, btree_id, pos,
@@ -1424,18 +1424,37 @@ static int bch2_trans_mark_pointer(struct btree_trans *trans,
 	ret = trans_get_key(trans, BTREE_ID_ALLOC,
 			    POS(p.ptr.dev, PTR_BUCKET_NR(ca, &p.ptr)),
 			    &iter, &k);
-	if (ret)
+	if (ret < 0)
 		return ret;
 
-	if (k.k->type != KEY_TYPE_alloc) {
-		bch_err_ratelimited(c, "pointer to nonexistent bucket %u:%zu",
-				    p.ptr.dev,
-				    PTR_BUCKET_NR(ca, &p.ptr));
-		ret = -1;
-		goto out;
-	}
+	if (!ret) {
+		/*
+		 * During journal replay, and if gc repairs alloc info at
+		 * runtime, the alloc info in the btree might not be up to date
+		 * yet - so, trust the in memory mark:
+		 */
+		struct bucket *g;
+		struct bucket_mark m;
 
-	u = bch2_alloc_unpack(k);
+		percpu_down_read(&c->mark_lock);
+		g	= bucket(ca, iter->pos.offset);
+		m	= READ_ONCE(g->mark);
+		u	= alloc_mem_to_key(g, m);
+		percpu_up_read(&c->mark_lock);
+	} else {
+		/*
+		 * Unless we're already updating that key:
+		 */
+		if (k.k->type != KEY_TYPE_alloc) {
+			bch_err_ratelimited(c, "pointer to nonexistent bucket %u:%zu",
+					    p.ptr.dev,
+					    PTR_BUCKET_NR(ca, &p.ptr));
+			ret = -1;
+			goto out;
+		}
+
+		u = bch2_alloc_unpack(k);
+	}
 
 	if (gen_after(u.gen, p.ptr.gen)) {
 		ret = 1;
@@ -1484,7 +1503,7 @@ static int bch2_trans_mark_stripe_ptr(struct btree_trans *trans,
 	int ret = 0;
 
 	ret = trans_get_key(trans, BTREE_ID_EC, POS(0, p.idx), &iter, &k);
-	if (ret)
+	if (ret < 0)
 		return ret;
 
 	if (k.k->type != KEY_TYPE_stripe) {
@@ -1599,7 +1618,7 @@ static int __bch2_trans_mark_reflink_p(struct btree_trans *trans,
 
 	ret = trans_get_key(trans, BTREE_ID_REFLINK,
 			    POS(0, idx), &iter, &k);
-	if (ret)
+	if (ret < 0)
 		return ret;
 
 	if (k.k->type != KEY_TYPE_reflink_v) {