dquot: cleanup space allocation / freeing routines

Get rid of the alloc_space, free_space, reserve_space, claim_space and
release_rsv dquot operations - they are always called from the filesystem
and if a filesystem really needs their own (which none currently does)
it can just call into it's own routine directly.

Move shared logic into the common __dquot_alloc_space,
dquot_claim_space_nodirty and __dquot_free_space low-level methods,
and rationalize the wrappers around it to move as much as possible
code into the common block for CONFIG_QUOTA vs not.  Also rename
all these helpers to be named dquot_* instead of vfs_dq_*.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index d34afad..0b90578 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4254,7 +4254,7 @@
 			return 0;
 		}
 		reserv_blks = ar->len;
-		while (ar->len && vfs_dq_alloc_block(ar->inode, ar->len)) {
+		while (ar->len && dquot_alloc_block(ar->inode, ar->len)) {
 			ar->flags |= EXT4_MB_HINT_NOPREALLOC;
 			ar->len--;
 		}
@@ -4331,7 +4331,7 @@
 	kmem_cache_free(ext4_ac_cachep, ac);
 out1:
 	if (inquota && ar->len < inquota)
-		vfs_dq_free_block(ar->inode, inquota - ar->len);
+		dquot_free_block(ar->inode, inquota - ar->len);
 out3:
 	if (!ar->len) {
 		if (!EXT4_I(ar->inode)->i_delalloc_reserved_flag)
@@ -4646,7 +4646,7 @@
 	sb->s_dirt = 1;
 error_return:
 	if (freed)
-		vfs_dq_free_block(inode, freed);
+		dquot_free_block(inode, freed);
 	brelse(bitmap_bh);
 	ext4_std_error(sb, err);
 	if (ac)