Btrfs: Fixes for 2.6.28-rc API changes

* open/close_bdev_excl -> open/close_bdev_exclusive
* blkdev_issue_discard takes a GFP mask now
* Fix blkdev_issue_discard usage now that it is enabled

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a0f3804..3a65c10 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2639,14 +2639,14 @@
 			/* open coding of lru_cache_add, also not exported */
 			page_cache_get(page);
 			if (!pagevec_add(&pvec, page))
-				__pagevec_lru_add(&pvec);
+				__pagevec_lru_add_file(&pvec);
 			__extent_read_full_page(tree, page, get_extent,
 						&bio, 0, &bio_flags);
 		}
 		page_cache_release(page);
 	}
 	if (pagevec_count(&pvec))
-		__pagevec_lru_add(&pvec);
+		__pagevec_lru_add_file(&pvec);
 	BUG_ON(!list_empty(pages));
 	if (bio)
 		submit_one_bio(READ, bio, 0, bio_flags);