[linux-lvm] resize2fs results in "permission denied"

[chris]

problem:
	after successful "lvextend -L +15G" , resize2fs gets "permission denied". 

strace says: 

	open("/dev/mapper/vg_phoesrv2b-varlog", O_RDONLY|O_EXCL) = -1 EACCES (Permission denied)
	open("/dev/mapper/vg_phoesrv2b-varlog", O_RDWR) = -1 EACCES (Permission denied)

ls: 
	brw-rw---- 1 root disk 254, 44 Apr 11 23:15 /dev/mapper/vg_phoesrv2b-varlog 

lvs: 
	varlog     vg_phoesrv2b -wi-ao--  25,00g

system:
	debian 7.8
	resize2fs 1.42.5 (29-Jul-2012)
	lvm2 2.02.95-8
	linux 3.18.9
	
never seen that one. what's going on?