nilfs2: mark buffer heads as delayed until the data is written to disk

Nilfs does not allocate new blocks on disk until they are actually
written to.  To implement fiemap, we need to deal with such blocks.

To allow successive fiemap patch to distinguish mapped but unallocated
regions, this marks buffer heads of those new blocks as delayed and
clears the flag after the blocks are written to disk.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

fs/nilfs2/inode.c

@@ -104,6 +104,7 @@ int nilfs_get_block(struct inode *inode, sector_t blkoff,
 		nilfs_transaction_commit(inode->i_sb); /* never fails */
 		/* Error handling should be detailed */
 		set_buffer_new(bh_result);
+		set_buffer_delay(bh_result);
 		map_bh(bh_result, inode->i_sb, 0); /* dbn must be changed
 						      to proper value */
 	} else if (ret == -ENOENT) {

fs/nilfs2/segment.c

@@ -1763,6 +1763,7 @@ static void nilfs_clear_copied_buffers(struct list_head *list, int err)
 				if (!err) {
 					set_buffer_uptodate(bh);
 					clear_buffer_dirty(bh);
+					clear_buffer_delay(bh);
 					clear_buffer_nilfs_volatile(bh);
 				}
 				brelse(bh); /* for b_assoc_buffers */
@@ -1889,6 +1890,7 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 				    b_assoc_buffers) {
 			set_buffer_uptodate(bh);
 			clear_buffer_dirty(bh);
+			clear_buffer_delay(bh);
 			clear_buffer_nilfs_volatile(bh);
 			clear_buffer_nilfs_redirected(bh);
 			if (bh == segbuf->sb_super_root) {