Can't free the ramdisk (initrd, pivot_root)

["H. Peter Anvin" <hpa@zytor.com>]

Hello friends,

I am trying the following setup, and it works beautifully, *except*
that I don't seem to be able to free the ramdisk memory at the end.
This is using the 2.4.3 stock kernel:

I load an initrd in "non-initrd" mode:

label single
        kernel vmlinuz
        append initrd=initrd.gz root=/dev/ram0 init=/linuxrc single

The initrd sets up a ramfs which is intended to become the root
filesystem, and then calls pivot_root:

[....]
umount /proc

# At this point, all that is mounted is /ram and /ram/usr

# Switch roots and run init
cd /ram
pivot_root /ram /ram/initrd
exec /sbin/init "$@"


(And yes, the /ram/initrd mount point directory does exist.)

This successfully runs init, and I can umount /initrd in the new
setup, but I cannot then destroy the ramdisk contents by calling
ioctl([/dev/ram0], BLKFLSBUF, 0) -- it always returns EBUSY.  What is
holding this ramdisk busy, especially since I could successfully
umount the filesystem?  Seems like a bug to me.

	-hpa
-- 
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