K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2012-12-28T23:08:30.663958Z
K 7
svn:log
V 756
Make it possible to atomically resume writes on the mount and account
the write start, by adding a variation of the vfs_write_resume(9)
which accepts flags.

Use the new function to prevent a deadlock between parallel suspension
and snapshotting a UFS mount.  The ffs_snapshot() code performed
vfs_write_resume() followed by vn_start_write() while owning the
snaplock.  If the suspension intervene between resume and
vn_start_write(), the deadlock occured after the suspending thread
tried to lock the snaplock, most typically during the write in the
ffs_copyonwrite().

Reported and tested by:	Andreas Longwitz <longwitz@incore.de>
Reviewed by:	mckusick
MFC after:	2 weeks
X-MFC-note:	make the vfs_write_resume(9) function a macro after the MFC,
	in HEAD

END