block: add a flag to make put_disk on partially initalized disks safer

Add a flag to indicate that __device_add_disk did grab a queue reference
so that disk_release only drops it if we actually had it.  This sort
out one of the major pitfals with partially initialized gendisk that
a lot of drivers did get wrong or still do.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/genhd.c b/block/genhd.c
index 9fa734c..c826db3 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -539,7 +539,10 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
         * Take an extra ref on queue which will be put on disk_release()
         * so that it sticks around as long as @disk is there.
         */
-       WARN_ON_ONCE(!blk_get_queue(disk->queue));
+       if (blk_get_queue(disk->queue))
+               set_bit(GD_QUEUE_REF, &disk->state);
+       else
+               WARN_ON_ONCE(1);
 
        disk_add_events(disk);
        blk_integrity_add(disk);
@@ -1107,7 +1110,7 @@ static void disk_release(struct device *dev)
        kfree(disk->random);
        xa_destroy(&disk->part_tbl);
        bdput(disk->part0);
-       if (disk->queue)
+       if (test_bit(GD_QUEUE_REF, &disk->state) && disk->queue)
                blk_put_queue(disk->queue);
        kfree(disk);
 }

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 6fc26f7..4d3ee8b 100644 (file)
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -153,6 +153,7 @@ struct gendisk {
        unsigned long state;
 #define GD_NEED_PART_SCAN              0
 #define GD_READ_ONLY                   1
+#define GD_QUEUE_REF                   2
        struct kobject *slave_dir;
 
        struct timer_rand_state *random;