block: remove REQ_NOWAIT_INLINE

We had a few issues with this code, and there's still a problem around
how we deal with error handling for chained/split bios. For now, just
revert the code and we'll try again with a thoroug solution. This
reverts commits:

e15c2ffa10 ("block: fix O_DIRECT error handling for bio fragments")
0eb6ddfb86 ("block: Fix __blkdev_direct_IO() for bio fragments")
6a43074e2f ("block: properly handle IOCB_NOWAIT for async O_DIRECT IO")
893a1c9720 ("blk-mq: allow REQ_NOWAIT to return an error inline")

Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -1958,13 +1958,9 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 	rq = blk_mq_get_request(q, bio, &data);
 	if (unlikely(!rq)) {
 		rq_qos_cleanup(q, bio);
-
-		cookie = BLK_QC_T_NONE;
-		if (bio->bi_opf & REQ_NOWAIT_INLINE)
-			cookie = BLK_QC_T_EAGAIN;
-		else if (bio->bi_opf & REQ_NOWAIT)
+		if (bio->bi_opf & REQ_NOWAIT)
 			bio_wouldblock_error(bio);
-		return cookie;
+		return BLK_QC_T_NONE;
 	}
 
 	trace_block_getrq(q, bio, bio->bi_opf);

fs/block_dev.c

@@ -345,24 +345,15 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 	struct bio *bio;
 	bool is_poll = (iocb->ki_flags & IOCB_HIPRI) != 0;
 	bool is_read = (iov_iter_rw(iter) == READ), is_sync;
-	bool nowait = (iocb->ki_flags & IOCB_NOWAIT) != 0;
 	loff_t pos = iocb->ki_pos;
 	blk_qc_t qc = BLK_QC_T_NONE;
-	gfp_t gfp;
-	int ret;
+	int ret = 0;
 
 	if ((pos | iov_iter_alignment(iter)) &
 	    (bdev_logical_block_size(bdev) - 1))
 		return -EINVAL;
 
-	if (nowait)
-		gfp = GFP_NOWAIT;
-	else
-		gfp = GFP_KERNEL;
-
-	bio = bio_alloc_bioset(gfp, nr_pages, &blkdev_dio_pool);
-	if (!bio)
-		return -EAGAIN;
+	bio = bio_alloc_bioset(GFP_KERNEL, nr_pages, &blkdev_dio_pool);
 
 	dio = container_of(bio, struct blkdev_dio, bio);
 	dio->is_sync = is_sync = is_sync_kiocb(iocb);
@@ -384,7 +375,6 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 	if (!is_poll)
 		blk_start_plug(&plug);
 
-	ret = 0;
 	for (;;) {
 		bio_set_dev(bio, bdev);
 		bio->bi_iter.bi_sector = pos >> 9;
@@ -409,14 +399,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 			task_io_account_write(bio->bi_iter.bi_size);
 		}
 
-		/*
-		 * Tell underlying layer to not block for resource shortage.
-		 * And if we would have blocked, return error inline instead
-		 * of through the bio->bi_end_io() callback.
-		 */
-		if (nowait)
-			bio->bi_opf |= (REQ_NOWAIT | REQ_NOWAIT_INLINE);
-
+		dio->size += bio->bi_iter.bi_size;
 		pos += bio->bi_iter.bi_size;
 
 		nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
@@ -428,13 +411,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 				polled = true;
 			}
 
-			dio->size += bio->bi_iter.bi_size;
 			qc = submit_bio(bio);
-			if (qc == BLK_QC_T_EAGAIN) {
-				dio->size -= bio->bi_iter.bi_size;
-				ret = -EAGAIN;
-				goto error;
-			}
 
 			if (polled)
 				WRITE_ONCE(iocb->ki_cookie, qc);
@@ -455,19 +432,8 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 			atomic_inc(&dio->ref);
 		}
 
-		dio->size += bio->bi_iter.bi_size;
-		qc = submit_bio(bio);
-		if (qc == BLK_QC_T_EAGAIN) {
-			dio->size -= bio->bi_iter.bi_size;
-			ret = -EAGAIN;
-			goto error;
-		}
-
-		bio = bio_alloc(gfp, nr_pages);
-		if (!bio) {
-			ret = -EAGAIN;
-			goto error;
-		}
+		submit_bio(bio);
+		bio = bio_alloc(GFP_KERNEL, nr_pages);
 	}
 
 	if (!is_poll)
@@ -487,7 +453,6 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 	}
 	__set_current_state(TASK_RUNNING);
 
-out:
 	if (!ret)
 		ret = blk_status_to_errno(dio->bio.bi_status);
 	if (likely(!ret))
@@ -495,10 +460,6 @@ out:
 
 	bio_put(&dio->bio);
 	return ret;
-error:
-	if (!is_poll)
-		blk_finish_plug(&plug);
-	goto out;
 }
 
 static ssize_t

include/linux/blk_types.h

@@ -311,7 +311,6 @@ enum req_flag_bits {
 	__REQ_RAHEAD,		/* read ahead, can fail anytime */
 	__REQ_BACKGROUND,	/* background IO */
 	__REQ_NOWAIT,           /* Don't wait if request will block */
-	__REQ_NOWAIT_INLINE,	/* Return would-block error inline */
 	/*
 	 * When a shared kthread needs to issue a bio for a cgroup, doing
 	 * so synchronously can lead to priority inversions as the kthread
@@ -346,7 +345,6 @@ enum req_flag_bits {
 #define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
 #define REQ_BACKGROUND		(1ULL << __REQ_BACKGROUND)
 #define REQ_NOWAIT		(1ULL << __REQ_NOWAIT)
-#define REQ_NOWAIT_INLINE	(1ULL << __REQ_NOWAIT_INLINE)
 #define REQ_CGROUP_PUNT		(1ULL << __REQ_CGROUP_PUNT)
 
 #define REQ_NOUNMAP		(1ULL << __REQ_NOUNMAP)
@@ -420,13 +418,12 @@ static inline int op_stat_group(unsigned int op)
 
 typedef unsigned int blk_qc_t;
 #define BLK_QC_T_NONE		-1U
-#define BLK_QC_T_EAGAIN		-2U
 #define BLK_QC_T_SHIFT		16
 #define BLK_QC_T_INTERNAL	(1U << 31)
 
 static inline bool blk_qc_t_valid(blk_qc_t cookie)
 {
-	return cookie != BLK_QC_T_NONE && cookie != BLK_QC_T_EAGAIN;
+	return cookie != BLK_QC_T_NONE;
 }
 
 static inline unsigned int blk_qc_t_to_queue_num(blk_qc_t cookie)