[GFS2] Use atomic_t for journal free blocks counter

This patch changes the counter which keeps track of the free
blocks in the journal to an atomic_t in preparation for the
following patch which will update the log reservation code.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index 52aaba9..1bba6ac 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -339,7 +339,7 @@
 
 	if (sdp->sd_args.ar_spectator) {
 		sdp->sd_jdesc = gfs2_jdesc_find(sdp, 0);
-		sdp->sd_log_blks_free = sdp->sd_jdesc->jd_blocks;
+		atomic_set(&sdp->sd_log_blks_free, sdp->sd_jdesc->jd_blocks);
 	} else {
 		if (sdp->sd_lockstruct.ls_jid >= gfs2_jindex_size(sdp)) {
 			fs_err(sdp, "can't mount journal #%u\n",
@@ -376,7 +376,7 @@
 			       sdp->sd_jdesc->jd_jid, error);
 			goto fail_jinode_gh;
 		}
-		sdp->sd_log_blks_free = sdp->sd_jdesc->jd_blocks;
+		atomic_set(&sdp->sd_log_blks_free, sdp->sd_jdesc->jd_blocks);
 	}
 
 	if (sdp->sd_lockstruct.ls_first) {