BDI_CAP_WRITEBACK
if (!(sb->s_bdi->capabilities & BDI_CAP_WRITEBACK))
(wb->bdi->capabilities & BDI_CAP_WRITEBACK))
return inode_to_bdi(mapping->host)->capabilities & BDI_CAP_WRITEBACK;
(bdi->capabilities & BDI_CAP_WRITEBACK) &&
bdi->capabilities = BDI_CAP_WRITEBACK;
if (!(bdi->capabilities & BDI_CAP_WRITEBACK))