On Tue 17-10-23 20:48:22, Christoph Hellwig wrote:
> From: Christian Brauner <brauner@xxxxxxxxxx>
>
> blk_report_disk_dead() has the following major callers:
>
> (1) del_gendisk()
> (2) blk_mark_disk_dead()
>
> Since del_gendisk() acquires disk->open_mutex it's clear that all
> callers are assumed to be called without disk->open_mutex held.
> In turn, blk_report_disk_dead() is called without disk->open_mutex held
> in del_gendisk().
>
> All callers of blk_mark_disk_dead() call it without disk->open_mutex as
> well.
>
> Ensure that it is clear that blk_report_disk_dead() is called without
> disk->open_mutex on purpose by asserting it and a comment in the code.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Sure. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
BTW, checking the callers I suspect that we might eventually hit some
locking issues with NVME and its ctrl->namespace_sem which is held while
calling blk_mark_disk_dead(). But I guess we'll deal with that once we see
the problem is real.
Honza
> ---
> block/genhd.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 4a16a424f57d4f..c9d06f72c587e8 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -559,6 +559,13 @@ static void blk_report_disk_dead(struct gendisk *disk, bool surprise)
> struct block_device *bdev;
> unsigned long idx;
>
> + /*
> + * On surprise disk removal, bdev_mark_dead() may call into file
> + * systems below. Make it clear that we're expecting to not hold
> + * disk->open_mutex.
> + */
> + lockdep_assert_not_held(&disk->open_mutex);
> +
> rcu_read_lock();
> xa_for_each(&disk->part_tbl, idx, bdev) {
> if (!kobject_get_unless_zero(&bdev->bd_device.kobj))
> --
> 2.39.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
