testcase: mount /dev/sdb10 /mnt touch /mnt/tmp/b umount /mnt mount /dev/sdb10 /mnt rm /mnt/tmp/b </mnt/tmp/b umount /mnt and watch blkdev_ioc line in /proc/slabinfo. Vanilla kernel leaks. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>