[dm-devel] [PATCH 4/8] block: support delayed holder registration

[Guenter Roeck]

On 8/20/21 8:08 AM, Christoph Hellwig wrote:
> Please try the patch below:
> 
> ---
>>From 7609266da56160d211662cd2fbe26570aad11b15 Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch at lst.de>
> Date: Fri, 20 Aug 2021 17:00:11 +0200
> Subject: mtd_blkdevs: don't hold del_mtd_blktrans_dev in
>   blktrans_{open,release}
> 
> There is nothing that this protects against except for slightly reducing
> the window when new opens can appear just before calling del_gendisk.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

A cautious

Tested-by: Guenter Roeck <linux at roeck-us.net>

Cautious because -next is a bit broken right now and I can not run a complete
test for all images.

Guenter

> ---
>   drivers/mtd/mtd_blkdevs.c | 5 -----
>   1 file changed, 5 deletions(-)
> 
> diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
> index 44bea3f65060..6b81a1c9ccbe 100644
> --- a/drivers/mtd/mtd_blkdevs.c
> +++ b/drivers/mtd/mtd_blkdevs.c
> @@ -207,7 +207,6 @@ static int blktrans_open(struct block_device *bdev, fmode_t mode)
>   	if (!dev)
>   		return -ERESTARTSYS; /* FIXME: busy loop! -arnd*/
>   
> -	mutex_lock(&mtd_table_mutex);
>   	mutex_lock(&dev->lock);
>   
>   	if (dev->open)
> @@ -233,7 +232,6 @@ static int blktrans_open(struct block_device *bdev, fmode_t mode)
>   unlock:
>   	dev->open++;
>   	mutex_unlock(&dev->lock);
> -	mutex_unlock(&mtd_table_mutex);
>   	blktrans_dev_put(dev);
>   	return ret;
>   
> @@ -244,7 +242,6 @@ static int blktrans_open(struct block_device *bdev, fmode_t mode)
>   	module_put(dev->tr->owner);
>   	kref_put(&dev->ref, blktrans_dev_release);
>   	mutex_unlock(&dev->lock);
> -	mutex_unlock(&mtd_table_mutex);
>   	blktrans_dev_put(dev);
>   	return ret;
>   }
> @@ -256,7 +253,6 @@ static void blktrans_release(struct gendisk *disk, fmode_t mode)
>   	if (!dev)
>   		return;
>   
> -	mutex_lock(&mtd_table_mutex);
>   	mutex_lock(&dev->lock);
>   
>   	if (--dev->open)
> @@ -272,7 +268,6 @@ static void blktrans_release(struct gendisk *disk, fmode_t mode)
>   	}
>   unlock:
>   	mutex_unlock(&dev->lock);
> -	mutex_unlock(&mtd_table_mutex);
>   	blktrans_dev_put(dev);
>   }
>   
>