resize_ffs hangs on needbuf

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

Hi

I am trying to grow a FFS filesystem from 10 Go to 20 Go on NetBSDD 6.0
(i386 Xen dom0). After running fsck -fy and updating the disklabel, I run 
resize_ffs.

The command hangs, waiting on needbuf, and all the machine gets unusable
until I kill it from ddb. I understand this is no RAM shortage since it 
has 1 Go of free memory (as reported by top, which is nice enough to 
keep running during the disaster).o

needbuf is a condvar in src/sys/kern/vfs_bio.c, it guards the bufmem_valimit
limit, which MD code can set it using buf_setvalimit(). That function 
does not seem to be called by i386/x86/xen code. 

What is the way around this problem?

-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost