GFS2: Use ->dirty_inode()

The aim of this patch is to use the newly enhanced ->dirty_inode()
super block operation to deal with atime updates, rather than
piggy backing that code into ->write_inode() as is currently
done.

The net result is a simplification of the code in various places
and a reduction of the number of gfs2_dinode_out() calls since
this is now implied by ->dirty_inode().

Some of the mark_inode_dirty() calls have been moved under glocks
in order to take advantage of then being able to avoid locking in
->dirty_inode() when we already have suitable locks.

One consequence is that generic_write_end() now correctly deals
with file size updates, so that we do not need a separate check
for that afterwards. This also, indirectly, means that fdatasync
should work correctly on GFS2 - the current code always syncs the
metadata whether it needs to or not.

Has survived testing with postmark (with and without atime) and
also fsx.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 2045d70..898e62e 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -1681,7 +1681,6 @@
 	const struct qstr *name = &dentry->d_name;
 	struct gfs2_dirent *dent, *prev = NULL;
 	struct buffer_head *bh;
-	int error;
 
 	/* Returns _either_ the entry (if its first in block) or the
 	   previous entry otherwise */
@@ -1710,22 +1709,15 @@
 	}
 	brelse(bh);
 
-	error = gfs2_meta_inode_buffer(dip, &bh);
-	if (error)
-		return error;
-
 	if (!dip->i_entries)
 		gfs2_consist_inode(dip);
-	gfs2_trans_add_bh(dip->i_gl, bh, 1);
 	dip->i_entries--;
 	dip->i_inode.i_mtime = dip->i_inode.i_ctime = CURRENT_TIME;
 	if (S_ISDIR(dentry->d_inode->i_mode))
 		drop_nlink(&dip->i_inode);
-	gfs2_dinode_out(dip, bh->b_data);
-	brelse(bh);
 	mark_inode_dirty(&dip->i_inode);
 
-	return error;
+	return 0;
 }
 
 /**