Re: [RFC PATCH v2 10/16] bcache: Add comments for blkdev_put() in registration code path

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Looks good.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>

On 04/19/2019 11:24 AM, Coly Li wrote:
> Add comments to explain why in register_bcache() blkdev_put() won't
> be called in two location. Add comments to explain why blkdev_put()
> must be called in register_cache() when cache_alloc() failed.
>
> Signed-off-by: Coly Li <colyli@xxxxxxx>
> ---
>   drivers/md/bcache/super.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index a435c506edba..83a7cb0e0e45 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -2191,6 +2191,12 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page,
>
>   	ret = cache_alloc(ca);
>   	if (ret != 0) {
> +		/*
> +		 * If we failed here, it means ca->kobj is not initialzed yet,
> +		 * kobject_put() won't be called and there is no chance to
> +		 * call blkdev_put() to bdev in bch_cache_release(). So we
> +		 * explictly call blkdev_put() here.
> +		 */
>   		blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
>   		if (ret == -ENOMEM)
>   			err = "cache_alloc(): -ENOMEM";
> @@ -2331,6 +2337,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>   		mutex_lock(&bch_register_lock);
>   		ret = register_bdev(sb, sb_page, bdev, dc);
>   		mutex_unlock(&bch_register_lock);
> +		/* blkdev_put() will be called in cached_dev_free() */
>   		if (ret < 0)
>   			goto err;
>   	} else {
> @@ -2339,6 +2346,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>   		if (!ca)
>   			goto err_close;
>
> +		/* blkdev_put() will be called in bch_cache_release() */
>   		if (register_cache(sb, sb_page, bdev, ca) != 0)
>   			goto err;
>   	}
>





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