[GFS2] Add nanosecond timestamp feature

This adds a nanosecond timestamp feature to the GFS2 filesystem. Due
to the way that the on-disk format works, older filesystems will just
appear to have this field set to zero. When mounted by an older version
of GFS2, the filesystem will simply ignore the extra fields so that
it will again appear to have whole second resolution, so that its
trivially backward compatible.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index a31a4b8..3ef0f05 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -178,11 +178,11 @@
 	di->di_blocks = be64_to_cpu(str->di_blocks);
 	gfs2_set_inode_blocks(&ip->i_inode);
 	ip->i_inode.i_atime.tv_sec = be64_to_cpu(str->di_atime);
-	ip->i_inode.i_atime.tv_nsec = 0;
+	ip->i_inode.i_atime.tv_nsec = be32_to_cpu(str->di_atime_nsec);
 	ip->i_inode.i_mtime.tv_sec = be64_to_cpu(str->di_mtime);
-	ip->i_inode.i_mtime.tv_nsec = 0;
+	ip->i_inode.i_mtime.tv_nsec = be32_to_cpu(str->di_mtime_nsec);
 	ip->i_inode.i_ctime.tv_sec = be64_to_cpu(str->di_ctime);
-	ip->i_inode.i_ctime.tv_nsec = 0;
+	ip->i_inode.i_ctime.tv_nsec = be32_to_cpu(str->di_ctime_nsec);
 
 	di->di_goal_meta = be64_to_cpu(str->di_goal_meta);
 	di->di_goal_data = be64_to_cpu(str->di_goal_data);
@@ -317,7 +317,7 @@
 	else
 		drop_nlink(&ip->i_inode);
 
-	ip->i_inode.i_ctime = CURRENT_TIME_SEC;
+	ip->i_inode.i_ctime = CURRENT_TIME;
 
 	gfs2_trans_add_bh(ip->i_gl, dibh, 1);
 	gfs2_dinode_out(ip, dibh->b_data);
@@ -648,6 +648,7 @@
 	struct gfs2_sbd *sdp = GFS2_SB(&dip->i_inode);
 	struct gfs2_dinode *di;
 	struct buffer_head *dibh;
+	struct timespec tv = CURRENT_TIME;
 
 	dibh = gfs2_meta_new(gl, inum->no_addr);
 	gfs2_trans_add_bh(gl, dibh, 1);
@@ -663,7 +664,7 @@
 	di->di_nlink = 0;
 	di->di_size = 0;
 	di->di_blocks = cpu_to_be64(1);
-	di->di_atime = di->di_mtime = di->di_ctime = cpu_to_be64(get_seconds());
+	di->di_atime = di->di_mtime = di->di_ctime = cpu_to_be64(tv.tv_sec);
 	di->di_major = cpu_to_be32(MAJOR(dev));
 	di->di_minor = cpu_to_be32(MINOR(dev));
 	di->di_goal_meta = di->di_goal_data = cpu_to_be64(inum->no_addr);
@@ -693,6 +694,9 @@
 	di->di_entries = 0;
 	memset(&di->__pad4, 0, sizeof(di->__pad4));
 	di->di_eattr = 0;
+	di->di_atime_nsec = cpu_to_be32(tv.tv_nsec);
+	di->di_mtime_nsec = cpu_to_be32(tv.tv_nsec);
+	di->di_ctime_nsec = cpu_to_be32(tv.tv_nsec);
 	memset(&di->di_reserved, 0, sizeof(di->di_reserved));
 
 	brelse(dibh);
@@ -1135,10 +1139,11 @@
 	struct gfs2_glock *gl = gh->gh_gl;
 	struct gfs2_sbd *sdp = gl->gl_sbd;
 	struct gfs2_inode *ip = gl->gl_object;
-	s64 curtime, quantum = gfs2_tune_get(sdp, gt_atime_quantum);
+	s64 quantum = gfs2_tune_get(sdp, gt_atime_quantum);
 	unsigned int state;
 	int flags;
 	int error;
+	struct timespec tv = CURRENT_TIME;
 
 	if (gfs2_assert_warn(sdp, gh->gh_flags & GL_ATIME) ||
 	    gfs2_assert_warn(sdp, !(gh->gh_flags & GL_ASYNC)) ||
@@ -1156,8 +1161,7 @@
 	    (sdp->sd_vfs->s_flags & MS_RDONLY))
 		return 0;
 
-	curtime = get_seconds();
-	if (curtime - ip->i_inode.i_atime.tv_sec >= quantum) {
+	if (tv.tv_sec - ip->i_inode.i_atime.tv_sec >= quantum) {
 		gfs2_glock_dq(gh);
 		gfs2_holder_reinit(LM_ST_EXCLUSIVE, gh->gh_flags & ~LM_FLAG_ANY,
 				   gh);
@@ -1168,8 +1172,8 @@
 		/* Verify that atime hasn't been updated while we were
 		   trying to get exclusive lock. */
 
-		curtime = get_seconds();
-		if (curtime - ip->i_inode.i_atime.tv_sec >= quantum) {
+		tv = CURRENT_TIME;
+		if (tv.tv_sec - ip->i_inode.i_atime.tv_sec >= quantum) {
 			struct buffer_head *dibh;
 			struct gfs2_dinode *di;
 
@@ -1183,11 +1187,12 @@
 			if (error)
 				goto fail_end_trans;
 
-			ip->i_inode.i_atime.tv_sec = curtime;
+			ip->i_inode.i_atime = tv;
 
 			gfs2_trans_add_bh(ip->i_gl, dibh, 1);
 			di = (struct gfs2_dinode *)dibh->b_data;
 			di->di_atime = cpu_to_be64(ip->i_inode.i_atime.tv_sec);
+			di->di_atime_nsec = cpu_to_be32(ip->i_inode.i_atime.tv_nsec);
 			brelse(dibh);
 
 			gfs2_trans_end(sdp);
@@ -1290,6 +1295,9 @@
 	str->di_entries = cpu_to_be32(di->di_entries);
 
 	str->di_eattr = cpu_to_be64(di->di_eattr);
+	str->di_atime_nsec = cpu_to_be32(ip->i_inode.i_atime.tv_nsec);
+	str->di_mtime_nsec = cpu_to_be32(ip->i_inode.i_mtime.tv_nsec);
+	str->di_ctime_nsec = cpu_to_be32(ip->i_inode.i_ctime.tv_nsec);
 }
 
 void gfs2_dinode_print(const struct gfs2_inode *ip)