block: replace BIO_QUEUE_ENTERED with BIO_CGROUP_ACCT

BIO_QUEUE_ENTERED is only used for cgroup accounting now, so rename
the flag and move setting it into the cgroup code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -336,16 +336,6 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio,
 		/* there isn't chance to merge the splitted bio */
 		split->bi_opf |= REQ_NOMERGE;
 
-		/*
-		 * Since we're recursing into make_request here, ensure
-		 * that we mark this bio as already having entered the queue.
-		 * If not, and the queue is going away, we can get stuck
-		 * forever on waiting for the queue reference to drop. But
-		 * that will never happen, as we're already holding a
-		 * reference to it.
-		 */
-		bio_set_flag(*bio, BIO_QUEUE_ENTERED);
-
 		bio_chain(split, *bio);
 		trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 		generic_make_request(*bio);

include/linux/blk-cgroup.h

@@ -607,12 +607,14 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,
 		u64_stats_update_begin(&bis->sync);
 
 		/*
-		 * If the bio is flagged with BIO_QUEUE_ENTERED it means this
-		 * is a split bio and we would have already accounted for the
-		 * size of the bio.
+		 * If the bio is flagged with BIO_CGROUP_ACCT it means this is a
+		 * split bio and we would have already accounted for the size of
+		 * the bio.
 		 */
-		if (!bio_flagged(bio, BIO_QUEUE_ENTERED))
+		if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
+			bio_set_flag(bio, BIO_CGROUP_ACCT);
 			bis->cur.bytes[rwd] += bio->bi_iter.bi_size;
+		}
 		bis->cur.ios[rwd]++;
 
 		u64_stats_update_end(&bis->sync);

include/linux/blk_types.h

@@ -220,7 +220,7 @@ enum {
 				 * throttling rules. Don't do it again. */
 	BIO_TRACE_COMPLETION,	/* bio_endio() should trace the final completion
 				 * of this bio. */
-	BIO_QUEUE_ENTERED,	/* can use blk_queue_enter_live() */
+	BIO_CGROUP_ACCT,	/* has been accounted to a cgroup */
 	BIO_TRACKED,		/* set if bio goes through the rq_qos path */
 	BIO_FLAG_LAST
 };