Now that we stop sd and sr from submitting passthrough commands from
their ->release methods we can and should start the drain before taking
->open_mutex, so that we can entirely prevent this kind of deadlock by
ensuring that the disk is clearly marked dead before open_mutex is
taken in del_gendisk.
This includes a revert of commit 7e04da2dc701 ("block: fix deadlock
between sd_remove & sd_release"), which was a partial fix for a similar
deadlock.
Reported-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Suggested-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
---
block/genhd.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 7026569fa8a0be..c15e8f1163664b 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -655,16 +655,6 @@ void del_gendisk(struct gendisk *disk)
if (WARN_ON_ONCE(!disk_live(disk) && !(disk->flags & GENHD_FL_HIDDEN)))
return;
- disk_del_events(disk);
-
- /*
- * Prevent new openers by unlinked the bdev inode.
- */
- mutex_lock(&disk->open_mutex);
- xa_for_each(&disk->part_tbl, idx, part)
- bdev_unhash(part);
- mutex_unlock(&disk->open_mutex);
-
/*
* Tell the file system to write back all dirty data and shut down if
* it hasn't been notified earlier.
@@ -673,10 +663,22 @@ void del_gendisk(struct gendisk *disk)
blk_report_disk_dead(disk, false);
/*
- * Drop all partitions now that the disk is marked dead.
+ * Then mark the disk dead to stop new requests from being served ASAP.
+ * This needs to happen before taking ->open_mutex to prevent deadlocks
+ * with SCSI ULPs that send passthrough commands from their ->release
+ * methods.
*/
- mutex_lock(&disk->open_mutex);
__blk_mark_disk_dead(disk);
+
+ disk_del_events(disk);
+
+ /*
+ * Prevent new openers by unlinking the bdev inode, and drop all
+ * partitions.
+ */
+ mutex_lock(&disk->open_mutex);
+ xa_for_each(&disk->part_tbl, idx, part)
+ bdev_unhash(part);
xa_for_each_start(&disk->part_tbl, idx, part, 1)
drop_partition(part);
mutex_unlock(&disk->open_mutex);
--
2.45.2
