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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 5/9] block: change the refcounting for partitions
Date: Thu, 22 Jul 2021 16:41:28 +0800	[thread overview]
Message-ID: <YPkvONK78vIEMrMI@T590> (raw)
In-Reply-To: <20210722075402.983367-6-hch@lst.de>

On Thu, Jul 22, 2021 at 09:53:58AM +0200, Christoph Hellwig wrote:
> Instead of acquiring an inode reference on open make sure partitions
> always hold device model references to the disk while alive, and switch
> open to grab only a device model reference to the opened block device.
> If that is a partition the disk reference is transitively held by the
> partition already.
> ---
>  block/partitions/core.c |  9 ++++++-
>  fs/block_dev.c          | 60 ++++++++++++++++-------------------------
>  2 files changed, 31 insertions(+), 38 deletions(-)
> 
> diff --git a/block/partitions/core.c b/block/partitions/core.c
> index 09c58a110a89..4f7a1a9cd544 100644
> --- a/block/partitions/core.c
> +++ b/block/partitions/core.c
> @@ -261,6 +261,7 @@ static void part_release(struct device *dev)
>  {
>  	if (MAJOR(dev->devt) == BLOCK_EXT_MAJOR)
>  		blk_free_ext_minor(MINOR(dev->devt));
> +	put_disk(dev_to_bdev(dev)->bd_disk);
>  	bdput(dev_to_bdev(dev));
>  }
>  
> @@ -349,9 +350,13 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
>  	if (xa_load(&disk->part_tbl, partno))
>  		return ERR_PTR(-EBUSY);
>  
> +	/* ensure we always have a reference to the whole disk */
> +	get_device(disk_to_dev(disk));
> +
> +	err = -ENOMEM;
>  	bdev = bdev_alloc(disk, partno);
>  	if (!bdev)
> -		return ERR_PTR(-ENOMEM);
> +		goto out_put_disk;
>  
>  	bdev->bd_start_sect = start;
>  	bdev_set_nr_sectors(bdev, len);
> @@ -420,6 +425,8 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
>  	device_del(pdev);
>  out_put:
>  	put_device(pdev);
> +out_put_disk:
> +	put_disk(disk);

put_disk() is only needed for failure of bdev_alloc(). Once bdev->bd_device
is initialized, the disk reference will be dropped via part_release().

Thanks,
Ming


  reply	other threads:[~2021-07-22  8:41 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
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 [this message]
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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