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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Josef Bacik <josef@toxicpanda.com>,
	David Sterba <dsterba@suse.com>,
	Naohiro Aota <naohiro.aota@wdc.com>,
	linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 3/9] block: unhash the whole device inode earlier
Date: Thu, 22 Jul 2021 16:19:42 +0800	[thread overview]
Message-ID: <YPkqHjNQpgvbUgBr@T590> (raw)
In-Reply-To: <20210722075402.983367-4-hch@lst.de>

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@lst.de>
> ---
>  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


  reply	other threads:[~2021-07-22  8:20 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-22  7:53 fixes and cleanups for block_device refcounting v2 Christoph Hellwig
2021-07-22  7:53 ` [PATCH 1/9] block: delay freeing the gendisk Christoph Hellwig
2021-07-22  7:53 ` [PATCH 2/9] block: assert the locking state in delete_partition Christoph Hellwig
2021-07-22 18:38   ` Chaitanya Kulkarni
2021-07-22  7:53 ` [PATCH 3/9] block: unhash the whole device inode earlier Christoph Hellwig
2021-07-22  8:19   ` Ming Lei [this message]
2021-07-22 13:12     ` Christoph Hellwig
2021-07-22  7:53 ` [PATCH 4/9] block: allocate bd_meta_info later in add_partitions Christoph Hellwig
2021-07-22  8:32   ` Ming Lei
2021-07-22  7:53 ` [PATCH 5/9] block: change the refcounting for partitions Christoph Hellwig
2021-07-22  8:41   ` Ming Lei
2021-07-22 13:12     ` Christoph Hellwig
2021-07-22  7:53 ` [PATCH 6/9] btrfs: store a block_device in struct btrfs_ordered_extent Christoph Hellwig
2021-07-22 12:58   ` David Sterba
2021-07-22 13:04     ` Christoph Hellwig
2021-07-22  7:54 ` [PATCH 7/9] loop: don't grab a reference to the block device Christoph Hellwig
2021-07-22  8:57   ` Ming Lei
2021-07-22 18:40   ` Chaitanya Kulkarni
2021-07-22  7:54 ` [PATCH 8/9] block: remove bdgrab Christoph Hellwig
2021-07-22  7:54 ` [PATCH 9/9] block: remove bdput Christoph Hellwig
2021-07-22 18:40   ` Chaitanya Kulkarni
2021-07-28  1:39 ` fixes and cleanups for block_device refcounting v2 Jens Axboe

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