bdi: replace BDI_CAP_NO_{WRITEBACK,ACCT_DIRTY} with a single flag

Replace the two negative flags that are always used together with a
single positive flag that indicates the writeback capability instead
of two related non-capabilities.  Also remove the pointless wrappers
to just check the flag.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/fs-writeback.c

@@ -2321,7 +2321,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
 
 			wb = locked_inode_to_wb_and_lock_list(inode);
 
-			WARN(bdi_cap_writeback_dirty(wb->bdi) &&
+			WARN((wb->bdi->capabilities & BDI_CAP_WRITEBACK) &&
 			     !test_bit(WB_registered, &wb->state),
 			     "bdi-%s not registered\n", bdi_dev_name(wb->bdi));
 
@@ -2346,7 +2346,8 @@ void __mark_inode_dirty(struct inode *inode, int flags)
 			 * to make sure background write-back happens
 			 * later.
 			 */
-			if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
+			if (wakeup_bdi &&
+			    (wb->bdi->capabilities & BDI_CAP_WRITEBACK))
 				wb_wakeup_delayed(wb);
 			return;
 		}
@@ -2581,7 +2582,7 @@ int write_inode_now(struct inode *inode, int sync)
 		.range_end = LLONG_MAX,
 	};
 
-	if (!mapping_cap_writeback_dirty(inode->i_mapping))
+	if (!mapping_can_writeback(inode->i_mapping))
 		wbc.nr_to_write = 0;
 
 	might_sleep();