GFS2: move toward a generic multi-block allocator

This patch is a revision of the one I previously posted.
I tried to integrate all the suggestions Steve gave.
The purpose of the patch is to change function gfs2_alloc_block
(allocate either a dinode block or an extent of data blocks)
to a more generic gfs2_alloc_blocks function that can
allocate both a dinode _and_ an extent of data blocks in the
same call. This will ultimately help us create a multi-block
reservation scheme to reduce file fragmentation.

This patch moves more toward a generic multi-block allocator that
takes a pointer to the number of data blocks to allocate, plus whether
or not to allocate a dinode. In theory, it could be called to allocate
(1) a single dinode block, (2) a group of one or more data blocks, or
(3) a dinode plus several data blocks.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index ae75319..f8485da 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -823,7 +823,7 @@
 	struct gfs2_dirent *dent;
 	struct qstr name = { .name = "", .len = 0, .hash = 0 };
 
-	error = gfs2_alloc_block(ip, &bn, &n, 0, NULL);
+	error = gfs2_alloc_blocks(ip, &bn, &n, 0, NULL);
 	if (error)
 		return NULL;
 	bh = gfs2_meta_new(ip->i_gl, bn);