This reverts commit c7b2eff059.
Hugh Dickins explains:
"It seems too little tested: "losetup -d /dev/loop0" fails with
EINVAL because nothing sets lo_thread; but even when you patch
loop_thread() to set lo->lo_thread = current, it can't survive
more than a few dozen iterations of the loop below (with a tmpfs
mounted on /tst):
j=0
cp /dev/zero /tst
while :
do
let j=j+1
echo "Doing pass $j"
losetup /dev/loop0 /tst/zero
mkfs -t ext2 -b 1024 /dev/loop0 >/dev/null 2>&1
mount -t ext2 /dev/loop0 /mnt
umount /mnt
losetup -d /dev/loop0
done
it collapses with failed ioctl then BUG_ON(!bio).
I think the original lo_done completion was more subtle and safe
than the kthread conversion has allowed for."
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
09c0dc6862