btrfs: move kthread_associate_blkcg out of btrfs_submit_compressed_write

btrfs_submit_compressed_write should not have to care if it is called
from a helper thread or not.  Move the kthread_associate_blkcg handling
into submit_one_async_extent, as that is the one caller that needs it.
Also move the assignment of REQ_CGROUP_PUNT into cow_file_range_async,
as that is the routine that sets up the helper thread offload.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.c

@@ -286,7 +286,6 @@ void btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 				 struct page **compressed_pages,
 				 unsigned int nr_pages,
 				 blk_opf_t write_flags,
-				 struct cgroup_subsys_state *blkcg_css,
 				 bool writeback)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
@@ -295,10 +294,6 @@ void btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
 	       IS_ALIGNED(len, fs_info->sectorsize));
 
-	if (blkcg_css) {
-		kthread_associate_blkcg(blkcg_css);
-		write_flags |= REQ_CGROUP_PUNT;
-	}
 	write_flags |= REQ_BTRFS_ONE_ORDERED;
 
 	cb = alloc_compressed_bio(inode, start, REQ_OP_WRITE | write_flags,
@@ -314,9 +309,6 @@ void btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	btrfs_add_compressed_bio_pages(cb);
 
 	btrfs_submit_bio(&cb->bbio, 0);
-
-	if (blkcg_css)
-		kthread_associate_blkcg(NULL);
 }
 
 /*

fs/btrfs/compression.h

@@ -92,7 +92,6 @@ void btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 				  struct page **compressed_pages,
 				  unsigned int nr_pages,
 				  blk_opf_t write_flags,
-				  struct cgroup_subsys_state *blkcg_css,
 				  bool writeback);
 void btrfs_submit_compressed_read(struct btrfs_bio *bbio, int mirror_num);
 

fs/btrfs/inode.c

@@ -1054,14 +1054,18 @@ static int submit_one_async_extent(struct btrfs_inode *inode,
 	extent_clear_unlock_delalloc(inode, start, end,
 			NULL, EXTENT_LOCKED | EXTENT_DELALLOC,
 			PAGE_UNLOCK | PAGE_START_WRITEBACK);
+
+	if (async_chunk->blkcg_css)
+		kthread_associate_blkcg(async_chunk->blkcg_css);
 	btrfs_submit_compressed_write(inode, start,	/* file_offset */
 			    async_extent->ram_size,	/* num_bytes */
 			    ins.objectid,		/* disk_bytenr */
 			    ins.offset,			/* compressed_len */
 			    async_extent->pages,	/* compressed_pages */
 			    async_extent->nr_pages,
-			    async_chunk->write_flags,
-			    async_chunk->blkcg_css, true);
+			    async_chunk->write_flags, true);
+	if (async_chunk->blkcg_css)
+		kthread_associate_blkcg(NULL);
 	*alloc_hint = ins.objectid + ins.offset;
 	kfree(async_extent);
 	return ret;
@@ -1613,6 +1617,7 @@ static int cow_file_range_async(struct btrfs_inode *inode,
 		if (blkcg_css != blkcg_root_css) {
 			css_get(blkcg_css);
 			async_chunk[i].blkcg_css = blkcg_css;
+			async_chunk[i].write_flags |= REQ_CGROUP_PUNT;
 		} else {
 			async_chunk[i].blkcg_css = NULL;
 		}
@@ -10348,8 +10353,7 @@ ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from,
 	btrfs_delalloc_release_extents(inode, num_bytes);
 
 	btrfs_submit_compressed_write(inode, start, num_bytes, ins.objectid,
-					  ins.offset, pages, nr_pages, 0, NULL,
-					  false);
+					  ins.offset, pages, nr_pages, 0, false);
 	ret = orig_count;
 	goto out;