kern/183293: Deadlock when modifying the zvol property of increasing the size.

[nikhil]

>Number:         183293
>Category:       kern
>Synopsis:       Deadlock when modifying the zvol property of increasing the size.
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Oct 25 07:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     nikhil
>Release:        base/stable/9
>Organization:
>Environment:
But the current kernel and then installed
>Description:
zfs enters in deadlock situation when modifying the zvol property
>How-To-Repeat:
Just create the volume and then do some IO on the at volume through iscsi and then increase the size of volume, it will get deadlock.
>Fix:
Just remove the holding the lock,

rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);

from function,

spa_sync_upgrades

in file spa.c



This fix is already present in base/releng/9.0

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