misc/163038: can not connect through ssh to server when /usr is 100% busy

[Eugen Konkov]

>Number:         163038
>Category:       misc
>Synopsis:       can not connect through ssh to server when /usr is 100% busy
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Dec 03 13:40:03 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Eugen Konkov
>Release:        9
>Organization:
ISP FreeLine
>Environment:
FreeBSD flux 9.0-CURRENT FreeBSD 9.0-CURRENT #4: Fri Jun 10 01:30:12 UTC 2011     :/usr/obj/usr/src/sys/PAE_KES  i386

>Description:
when hard drive is 100% busy and I/O operations on /usr slice
you can not connect to system until IO complete

dump -0L -f - /usr | gzip -2 | ssh -c blowfish u at u dd of=/usr/sharedzone/snap/dump-usr.gz

df -h
/dev/ad0s1f    1.8T     21G    1.6T     1%    /usr

It seems that dump lock slice while doing snapshot

tty also locked if I try to 'cd to /usr/.snap'
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: