bcachefs: Some project id fixes

Inode options that are accessible via the xattr interface are stored
with a +1 bias, so that a value of 0 means unset. We weren't handling
this consistently.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs-ioctl.c

@@ -138,6 +138,10 @@ static int bch2_ioc_fssetxattr(struct bch_fs *c,
 	if (fa.fsx_projid >= U32_MAX)
 		return -EINVAL;
 
+	/*
+	 * inode fields accessible via the xattr interface are stored with a +1
+	 * bias, so that 0 means unset:
+	 */
 	s.projid = fa.fsx_projid + 1;
 
 	ret = mnt_want_write_file(file);
@@ -151,7 +155,7 @@ static int bch2_ioc_fssetxattr(struct bch_fs *c,
 	}
 
 	mutex_lock(&inode->ei_update_lock);
-	ret = bch2_set_projid(c, inode, s.projid);
+	ret = bch2_set_projid(c, inode, fa.fsx_projid);
 	if (ret)
 		goto err_unlock;
 

fs/bcachefs/xattr.c

@@ -513,7 +513,11 @@ static int bch2_xattr_bcachefs_set(const struct xattr_handler *handler,
 
 	mutex_lock(&inode->ei_update_lock);
 	if (inode_opt_id == Inode_opt_project) {
-		ret = bch2_set_projid(c, inode, s.v);
+		/*
+		 * inode fields accessible via the xattr interface are stored
+		 * with a +1 bias, so that 0 means unset:
+		 */
+		ret = bch2_set_projid(c, inode, s.v ? s.v - 1 : 0);
 		if (ret)
 			goto err;
 	}