On Thu, Jul 22, 2021 at 09:53:56AM +0200, Christoph Hellwig wrote:
> Unhash the whole device inode early in del_gendisk. This allows to
> remove the first GENHD_FL_UP check in the open path as we simply
> won't find a just removed inode. The second non-racy check after
> taking open_mutex is still kept.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> block/genhd.c | 7 +------
> fs/block_dev.c | 2 +-
> 2 files changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 298ee78c1bda..716f5ca479ad 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -585,6 +585,7 @@ void del_gendisk(struct gendisk *disk)
> disk_del_events(disk);
>
> mutex_lock(&disk->open_mutex);
> + remove_inode_hash(disk->part0->bd_inode);
> disk->flags &= ~GENHD_FL_UP;
> blk_drop_partitions(disk);
> mutex_unlock(&disk->open_mutex);
> @@ -592,12 +593,6 @@ void del_gendisk(struct gendisk *disk)
> fsync_bdev(disk->part0);
> __invalidate_device(disk->part0, true);
>
> - /*
> - * Unhash the bdev inode for this device so that it can't be looked
> - * up any more even if openers still hold references to it.
> - */
> - remove_inode_hash(disk->part0->bd_inode);
> -
> set_capacity(disk, 0);
>
> if (!(disk->flags & GENHD_FL_HIDDEN)) {
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 9ef4f1fc2cb0..932f4034ad66 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1340,7 +1340,7 @@ struct block_device *blkdev_get_no_open(dev_t dev)
> disk = bdev->bd_disk;
> if (!kobject_get_unless_zero(&disk_to_dev(disk)->kobj))
> goto bdput;
> - if ((disk->flags & (GENHD_FL_UP | GENHD_FL_HIDDEN)) != GENHD_FL_UP)
> + if (disk->flags & GENHD_FL_HIDDEN)
But del_gendisk() can be called just between bdget() and checking GENHD_FL_UP.
And not see difference by moving remove_inode_hash() with disk open_mutex held.
Thanks,
Ming
