Re: [PATCH 4/5] block: assert that we're not holding open_mutex over blk_report_disk_dead

[Ming Lei <ming.lei@redhat.com>]

On Tue, Oct 17, 2023 at 08:48:22PM +0200, Christoph Hellwig wrote:
> From: Christian Brauner <brauner@kernel.org>
> 
> 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@kernel.org>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  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))

Reviewed-by: Ming Lei <ming.lei@redhat.com>


thanks, 
Ming