bcachefs: bch2_sb_maybe_downgrade(), bch2_sb_upgrade()

Add some new helpers, and fix upgrade/downgrade in bch2_fs_initialize().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/recovery.c

@@ -1166,8 +1166,7 @@ static void check_version_upgrade(struct bch_fs *c)
 		c->opts.fix_errors	= FSCK_OPT_YES;
 
 		mutex_lock(&c->sb_lock);
-		c->disk_sb.sb->version = cpu_to_le16(new_version);
-		c->disk_sb.sb->features[0] |= cpu_to_le64(BCH_SB_FEATURES_ALL);
+		bch2_sb_upgrade(c, new_version);
 		mutex_unlock(&c->sb_lock);
 
 		printbuf_exit(&buf);
@@ -1525,10 +1524,11 @@ int bch2_fs_initialize(struct bch_fs *c)
 	c->disk_sb.sb->compat[0] |= cpu_to_le64(1ULL << BCH_COMPAT_extents_above_btree_updates_done);
 	c->disk_sb.sb->compat[0] |= cpu_to_le64(1ULL << BCH_COMPAT_bformat_overflow_done);
 
+	bch2_sb_maybe_downgrade(c);
+
 	if (c->opts.version_upgrade != BCH_VERSION_UPGRADE_none) {
-		c->disk_sb.sb->version = cpu_to_le16(bcachefs_metadata_version_current);
+		bch2_sb_upgrade(c, bcachefs_metadata_version_current);
 		SET_BCH_SB_VERSION_UPGRADE_COMPLETE(c->disk_sb.sb, bcachefs_metadata_version_current);
-		c->disk_sb.sb->features[0] |= cpu_to_le64(BCH_SB_FEATURES_ALL);
 		bch2_write_super(c);
 	}
 	mutex_unlock(&c->sb_lock);

fs/bcachefs/super-io.c

@@ -1204,17 +1204,10 @@ int bch2_sb_clean_validate_late(struct bch_fs *c, struct bch_sb_field_clean *cle
 	return 0;
 }
 
-int bch2_fs_mark_dirty(struct bch_fs *c)
+/* Downgrade if superblock is at a higher version than currently supported: */
+void bch2_sb_maybe_downgrade(struct bch_fs *c)
 {
-	int ret;
-
-	/*
-	 * Unconditionally write superblock, to verify it hasn't changed before
-	 * we go rw:
-	 */
-
-	mutex_lock(&c->sb_lock);
-	SET_BCH_SB_CLEAN(c->disk_sb.sb, false);
+	lockdep_assert_held(&c->sb_lock);
 
 	/*
 	 * Downgrade, if superblock is at a higher version than currently
@@ -1227,8 +1220,31 @@ int bch2_fs_mark_dirty(struct bch_fs *c)
 	if (c->sb.version_min > bcachefs_metadata_version_current)
 		c->disk_sb.sb->version_min = cpu_to_le16(bcachefs_metadata_version_current);
 	c->disk_sb.sb->compat[0] &= cpu_to_le64((1ULL << BCH_COMPAT_NR) - 1);
+}
+
+void bch2_sb_upgrade(struct bch_fs *c, unsigned new_version)
+{
+	lockdep_assert_held(&c->sb_lock);
 
+	c->disk_sb.sb->version = cpu_to_le16(new_version);
+	c->disk_sb.sb->features[0] |= cpu_to_le64(BCH_SB_FEATURES_ALL);
+}
+
+int bch2_fs_mark_dirty(struct bch_fs *c)
+{
+	int ret;
+
+	/*
+	 * Unconditionally write superblock, to verify it hasn't changed before
+	 * we go rw:
+	 */
+
+	mutex_lock(&c->sb_lock);
+	SET_BCH_SB_CLEAN(c->disk_sb.sb, false);
+
+	bch2_sb_maybe_downgrade(c);
 	c->disk_sb.sb->features[0] |= cpu_to_le64(BCH_SB_FEATURES_ALWAYS);
+
 	ret = bch2_write_super(c);
 	mutex_unlock(&c->sb_lock);
 

fs/bcachefs/super-io.h

@@ -124,6 +124,9 @@ void bch2_journal_super_entries_add_common(struct bch_fs *,
 
 int bch2_sb_clean_validate_late(struct bch_fs *, struct bch_sb_field_clean *, int);
 
+void bch2_sb_maybe_downgrade(struct bch_fs *);
+void bch2_sb_upgrade(struct bch_fs *, unsigned);
+
 int bch2_fs_mark_dirty(struct bch_fs *);
 void bch2_fs_mark_clean(struct bch_fs *);