block: drain file system I/O on del_gendisk

Instead of delaying draining of file system I/O related items like the
blk-qos queues, the integrity read workqueue and timeouts only when the
request_queue is removed, do that when del_gendisk is called.  This is
important for SCSI where the upper level drivers that control the gendisk
are separate entities, and the disk can be freed much earlier than the
request_queue, or can even be unbound without tearing down the queue.

Fixes: edb0872 ("block: move the bdi from the request_queue to the gendisk")
Reported-by: Ming Lei <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Tested-by: Darrick J. Wong <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Tested-by: Yi Zhang <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: Christoph Hellwig

block/blk-core.c

@@ -49,7 +49,6 @@
 #include "blk-mq.h"
 #include "blk-mq-sched.h"
 #include "blk-pm.h"
-#include "blk-rq-qos.h"
 
 struct dentry *blk_debugfs_root;
 
@@ -337,23 +336,25 @@ void blk_put_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_put_queue);
 
-void blk_set_queue_dying(struct request_queue *q)
+void blk_queue_start_drain(struct request_queue *q)
 {
-	blk_queue_flag_set(QUEUE_FLAG_DYING, q);
-
 	/*
 	 * When queue DYING flag is set, we need to block new req
 	 * entering queue, so we call blk_freeze_queue_start() to
 	 * prevent I/O from crossing blk_queue_enter().
 	 */
 	blk_freeze_queue_start(q);
-
 	if (queue_is_mq(q))
 		blk_mq_wake_waiters(q);
-
 	/* Make blk_queue_enter() reexamine the DYING flag. */
 	wake_up_all(&q->mq_freeze_wq);
 }
+
+void blk_set_queue_dying(struct request_queue *q)
+{
+	blk_queue_flag_set(QUEUE_FLAG_DYING, q);
+	blk_queue_start_drain(q);
+}
 EXPORT_SYMBOL_GPL(blk_set_queue_dying);
 
 /**
@@ -385,13 +386,8 @@ void blk_cleanup_queue(struct request_queue *q)
 	 */
 	blk_freeze_queue(q);
 
-	rq_qos_exit(q);
-
 	blk_queue_flag_set(QUEUE_FLAG_DEAD, q);
 
-	/* for synchronous bio-based driver finish in-flight integrity i/o */
-	blk_flush_integrity();
-
 	blk_sync_queue(q);
 	if (queue_is_mq(q))
 		blk_mq_exit_queue(q);
@@ -474,11 +470,12 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
 
 static inline int bio_queue_enter(struct bio *bio)
 {
-	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
+	struct gendisk *disk = bio->bi_bdev->bd_disk;
+	struct request_queue *q = disk->queue;
 
 	while (!blk_try_enter_queue(q, false)) {
 		if (bio->bi_opf & REQ_NOWAIT) {
-			if (blk_queue_dying(q))
+			if (test_bit(GD_DEAD, &disk->state))
 				goto dead;
 			bio_wouldblock_error(bio);
 			return -EBUSY;
@@ -495,8 +492,8 @@ static inline int bio_queue_enter(struct bio *bio)
 		wait_event(q->mq_freeze_wq,
 			   (!q->mq_freeze_depth &&
 			    blk_pm_resume_queue(false, q)) ||
-			   blk_queue_dying(q));
-		if (blk_queue_dying(q))
+			   test_bit(GD_DEAD, &disk->state));
+		if (test_bit(GD_DEAD, &disk->state))
 			goto dead;
 	}
 

block/blk.h

@@ -51,6 +51,7 @@ struct blk_flush_queue *blk_alloc_flush_queue(int node, int cmd_size,
 void blk_free_flush_queue(struct blk_flush_queue *q);
 
 void blk_freeze_queue(struct request_queue *q);
+void blk_queue_start_drain(struct request_queue *q);
 
 #define BIO_INLINE_VECS 4
 struct bio_vec *bvec_alloc(mempool_t *pool, unsigned short *nr_vecs,

block/genhd.c

@@ -26,6 +26,7 @@
 #include <linux/badblocks.h>
 
 #include "blk.h"
+#include "blk-rq-qos.h"
 
 static struct kobject *block_depr;
 
@@ -559,6 +560,8 @@ EXPORT_SYMBOL(device_add_disk);
  */
 void del_gendisk(struct gendisk *disk)
 {
+	struct request_queue *q = disk->queue;
+
 	might_sleep();
 
 	if (WARN_ON_ONCE(!disk_live(disk) && !(disk->flags & GENHD_FL_HIDDEN)))
@@ -575,8 +578,26 @@ void del_gendisk(struct gendisk *disk)
 	fsync_bdev(disk->part0);
 	__invalidate_device(disk->part0, true);
 
+	/*
+	 * Fail any new I/O.
+	 */
+	set_bit(GD_DEAD, &disk->state);
 	set_capacity(disk, 0);
 
+	/*
+	 * Prevent new I/O from crossing bio_queue_enter().
+	 */
+	blk_queue_start_drain(q);
+	blk_mq_freeze_queue_wait(q);
+
+	rq_qos_exit(q);
+	blk_sync_queue(q);
+	blk_flush_integrity();
+	/*
+	 * Allow using passthrough request again after the queue is torn down.
+	 */
+	blk_mq_unfreeze_queue(q);
+
 	if (!(disk->flags & GENHD_FL_HIDDEN)) {
 		sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
 

include/linux/genhd.h

@@ -149,6 +149,7 @@ struct gendisk {
 	unsigned long state;
 #define GD_NEED_PART_SCAN		0
 #define GD_READ_ONLY			1
+#define GD_DEAD				2
 
 	struct mutex open_mutex;	/* open/close mutex */
 	unsigned open_partitions;	/* number of open partitions */