bcachefs: Start snapshots before bch2_gc()

bch2_gc may require snapshots to be started - the repair path when
checking the reflink btree may do updates to the extents btree.

This moves bch2_fs_initialize_subvolumes() and bch2_fs_snapshots_start()
to before bch2_gc() - since we haven't gone RW yet, the updates in
bch2_fs_initialize_subvolumes() are done via the journal replay keys
list, so it's fine to do this before bch2_gc().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/recovery.c

@@ -1250,6 +1250,20 @@ int bch2_fs_recovery(struct bch_fs *c)
 
 	bch2_stripes_heap_start(c);
 
+	if (c->sb.version < bcachefs_metadata_version_snapshot_2) {
+		err = "error creating root snapshot node";
+		ret = bch2_fs_initialize_subvolumes(c);
+		if (ret)
+			goto err;
+	}
+
+	bch_verbose(c, "reading snapshots table");
+	err = "error reading snapshots table";
+	ret = bch2_fs_snapshots_start(c);
+	if (ret)
+		goto err;
+	bch_verbose(c, "reading snapshots done");
+
 	if (c->opts.fsck) {
 		bool metadata_only = c->opts.norecovery;
 
@@ -1262,20 +1276,6 @@ int bch2_fs_recovery(struct bch_fs *c)
 
 		set_bit(BCH_FS_INITIAL_GC_DONE, &c->flags);
 
-		if (c->sb.version < bcachefs_metadata_version_snapshot_2) {
-			err = "error creating root snapshot node";
-			ret = bch2_fs_initialize_subvolumes(c);
-			if (ret)
-				goto err;
-		}
-
-		bch_verbose(c, "reading snapshots table");
-		err = "error reading snapshots table";
-		ret = bch2_fs_snapshots_start(c);
-		if (ret)
-			goto err;
-		bch_verbose(c, "reading snapshots done");
-
 		set_bit(BCH_FS_MAY_GO_RW, &c->flags);
 
 		bch_info(c, "starting journal replay, %zu keys", c->journal_keys.nr);
@@ -1343,20 +1343,6 @@ int bch2_fs_recovery(struct bch_fs *c)
 		if (c->opts.norecovery)
 			goto out;
 
-		if (c->sb.version < bcachefs_metadata_version_snapshot_2) {
-			err = "error creating root snapshot node";
-			ret = bch2_fs_initialize_subvolumes(c);
-			if (ret)
-				goto err;
-		}
-
-		bch_verbose(c, "reading snapshots table");
-		err = "error reading snapshots table";
-		ret = bch2_fs_snapshots_start(c);
-		if (ret)
-			goto err;
-		bch_verbose(c, "reading snapshots done");
-
 		set_bit(BCH_FS_MAY_GO_RW, &c->flags);
 
 		bch_verbose(c, "starting journal replay, %zu keys", c->journal_keys.nr);