btrfs, mm: remove the punt_to_cgroup field in struct writeback_control

punt_to_cgroup is only used by extent_write_locked_range, but that
function also directly controls the bio flags for the actual submission.
Remove th punt_to_cgroup field, and just set REQ_CGROUP_PUNT directly
in extent_write_locked_range.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -2533,13 +2533,13 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end)
 		.sync_mode	= WB_SYNC_ALL,
 		.range_start	= start,
 		.range_end	= end + 1,
-		/* We're called from an async helper function */
-		.punt_to_cgroup	= 1,
 		.no_cgroup_owner = 1,
 	};
 	struct btrfs_bio_ctrl bio_ctrl = {
 		.wbc = &wbc_writepages,
-		.opf = REQ_OP_WRITE | wbc_to_write_flags(&wbc_writepages),
+		/* We're called from an async helper function */
+		.opf = REQ_OP_WRITE | REQ_CGROUP_PUNT |
+			wbc_to_write_flags(&wbc_writepages),
 		.extent_locked = 1,
 	};
 

include/linux/writeback.h

@@ -70,8 +70,6 @@ struct writeback_control {
 	 */
 	unsigned no_cgroup_owner:1;
 
-	unsigned punt_to_cgroup:1;	/* cgrp punting, see __REQ_CGROUP_PUNT */
-
 	/* To enable batching of swap writes to non-block-device backends,
 	 * "plug" can be set point to a 'struct swap_iocb *'.  When all swap
 	 * writes have been submitted, if with swap_iocb is not NULL,
@@ -97,9 +95,6 @@ static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
 {
 	blk_opf_t flags = 0;
 
-	if (wbc->punt_to_cgroup)
-		flags = REQ_CGROUP_PUNT;
-
 	if (wbc->sync_mode == WB_SYNC_ALL)
 		flags |= REQ_SYNC;
 	else if (wbc->for_kupdate || wbc->for_background)