I'm not sure whom this patch should be send to, so I'm posting it here.

this patch fixes the problem that huge inode cache
can make invalidate_inodes() calls very long. Meanwhile
lock_kernel() and inode_lock are being held and system
can freeze for seconds.
I detected this problem on kernel with 4gb split. When inode cache
was 2.5Gb (1,000,000 of inodes in cache) it took seconds to umount
or turn quota off.
This patch is against 2.4.22 kernel. But as far as I can see the problem
still exists in 2.6 kernels.
This patch introduces per-super block inode list which makes
possible to scan sb's only inodes when doing umount.

Kirill