[PATCH v2 1/2] block: set QUEUE_FLAG_DYING unconditionally in blk_mark_disk_dead()

[胡连勤]

Disks created via blk_mq_alloc_disk_for_queue() (e.g. SCSI SD disks)
do not have GD_OWNS_QUEUE set.  Currently __blk_mark_disk_dead() only
sets QUEUE_FLAG_DYING when GD_OWNS_QUEUE is set, so for such disks
blk_queue_enter() and __bio_queue_enter() cannot detect the dying
state via blk_queue_dying() and remain blocked waiting for I/O that
will never complete after surprise removal.

blk_mark_disk_dead() is the explicit "surprise removal" API -- the
caller has already decided the disk is dead.  Setting QUEUE_FLAG_DYING
unconditionally here is appropriate: any in-flight I/O from other
threads should get -ENODEV immediately from blk_queue_enter()
regardless of GD_OWNS_QUEUE ownership.

For disks that already have GD_OWNS_QUEUE set, __blk_mark_disk_dead()
will set the flag again which is harmless.

Fixes: 6f8191fdf41d ("block: simplify disk shutdown")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Lianqin Hu <hulianqin@xxxxxxxx>
---

Changes in v2:
- Split into a two-patch series for independent review by block and SCSI maintainers.
- This is the block layer part extracted from v1.
- Link to v1: https://lore.kernel.org/all/TYUPR06MB6217566CFD33F57D3AE46816D2CF2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

 block/genhd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/genhd.c b/block/genhd.c
index df2c3c69b467..7b089e2d52c4 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -681,6 +681,7 @@ static bool __blk_mark_disk_dead(struct gendisk *disk)
  */
 void blk_mark_disk_dead(struct gendisk *disk)
 {
+	blk_queue_flag_set(QUEUE_FLAG_DYING, disk->queue);
 	__blk_mark_disk_dead(disk);
 	blk_report_disk_dead(disk, true);
 }

-- 
2.39.0