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>,
linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 3/8] block: grab a device model reference in blkdev_get_no_open
Date: Thu, 22 Jul 2021 10:47:08 +0800 [thread overview]
Message-ID: <YPjcLDXYKbN1yl22@T590> (raw)
In-Reply-To: <20210721153523.103818-4-hch@lst.de>
On Wed, Jul 21, 2021 at 05:35:18PM +0200, Christoph Hellwig wrote:
> Opening a block device needs to ensure it is fully present instead of
> just the allocated memory. Switch from an inode reference as obtained
> by bdget to a full device model reference.
>
> In fact we should not use inode references for anything in the block
> layer. There are three users left, two can be trivially removed
> and the third (xen-blkfront) is a complete mess that needs more
> attention.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/block_dev.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 9ef4f1fc2cb0..24a6970f3623 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1342,9 +1342,16 @@ struct block_device *blkdev_get_no_open(dev_t dev)
> goto bdput;
> if ((disk->flags & (GENHD_FL_UP | GENHD_FL_HIDDEN)) != GENHD_FL_UP)
> goto put_disk;
> - if (!try_module_get(bdev->bd_disk->fops->owner))
> + if (!try_module_get(disk->fops->owner))
> goto put_disk;
> +
> + /* switch to a device model reference instead of the inode one: */
> + if (!kobject_get_unless_zero(&bdev->bd_device.kobj))
If bdev->bd_device.kobj is grabbed in every open, getting disk reference might
be moved into add_partition, and drop it in part_release(). Then we can avoid
extra disk reference in open/close().
Not mention two disk references are actually grabbed in case of opening disk.
Thanks,
Ming
next prev parent reply other threads:[~2021-07-22 2:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-21 15:35 fixes and cleanups for block_device refcounting Christoph Hellwig
2021-07-21 15:35 ` [PATCH 1/8] block: delay freeing the gendisk Christoph Hellwig
2021-07-22 2:05 ` Ming Lei
2021-07-21 15:35 ` [PATCH 2/8] block: assert the locking state in delete_partition Christoph Hellwig
2021-07-22 2:06 ` Ming Lei
2021-07-21 15:35 ` [PATCH 3/8] block: grab a device model reference in blkdev_get_no_open Christoph Hellwig
2021-07-22 2:47 ` Ming Lei [this message]
2021-07-21 15:35 ` [PATCH 4/8] block: don't grab a reference to the whole device in blkdev_get_part Christoph Hellwig
2021-07-21 15:35 ` [PATCH 5/8] btrfs: no need to grab a reference to disk->part0 Christoph Hellwig
2021-07-21 16:15 ` David Sterba
2021-07-21 15:35 ` [PATCH 6/8] loop: don't grab a reference to the block device Christoph Hellwig
2021-07-21 15:35 ` [PATCH 7/8] block: remove bdgrab Christoph Hellwig
2021-07-21 15:35 ` [PATCH 8/8] block: remove bdget/bdput Christoph Hellwig
2021-07-21 20:52 ` fixes and cleanups for block_device refcounting Josef Bacik
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