Re: ramdisk contents lost with 2.6

[Andrew Morton <akpm@osdl.org>]

Olaf Hering <olh@suse.de> wrote:
>
> Good morning,
> 
> is it only me or is the file really gone with 2.6?
> 
> umount -v /mnt
> /sbin/mkfs.ext2 /dev/ram3
> mount -v /dev/ram3 /mnt
> cp /etc/hosts /mnt
> sync
> umount -v /mnt
> mount -v /dev/ram3 /mnt
> ls -l /mnt/hosts
> umount -v /mnt
> 
> 
> works ok with 2.4.
> 

Yup.  Because the kernel considers the ramdisk as being "memory backed" it
doesn't do writeback into the blockdev pagecache.  If you remove the
memory-backed flag, ramdisk contributes to dirty memory in undesirable
ways.  That memory-backed flag is too overloaded and needs to be split up.

It's something I need to fix, but nobody seemed to be hurting from it up to
now so I figured it could wait until after 2.6.0.