K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2017-07-21T18:36:17.677489Z
K 7
svn:log
V 495
Unlock correct lock in ffs_snapblkfree().

It is possible for ffs_snapblkfree() to race and lock snaplock while
the devvp snapdata is instantiated, but no snapshots exist.  In this
case the loop over snapshots in ffs_snapblkfree() is not executed, and
the local variable vp is left initialized to NULL.

Unlock using &sn->sn_lock and not vp->v_vnlock.  For the inodes on the
snapshot list, the locks are same.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

END