[GFS2] Fix a bug: scheduling under a spinlock

At some stage, a mutex was added to gfs2_glock_put() without
checking all its call sites. Two of them were called from
under a spinlock causing random delays at various points and
crashes.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index b0dd0b9..9e32e0f 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -578,6 +578,7 @@
 	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
 	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_rg);
 	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_databuf);
+	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_hdrs);
 	gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));
 
 	sdp->sd_log_flush_head = sdp->sd_log_head;