Re: [PATCH 04/13] block: add a disk_openers helper
- To: Christoph Hellwig <hch@lst.de>
- Cc: Jens Axboe <axboe@kernel.dk>, Josef Bacik <josef@toxicpanda.com>, Minchan Kim <minchan@kernel.org>, Nitin Gupta <ngupta@vflare.org>, Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>, Jan Kara <jack@suse.cz>, "Darrick J . Wong" <djwong@kernel.org>, Ming Lei <ming.lei@redhat.com>, linux-block@vger.kernel.org, nbd@other.debian.org
- Subject: Re: [PATCH 04/13] block: add a disk_openers helper
- From: Jan Kara <jack@suse.cz>
- Date: Thu, 24 Mar 2022 14:24:42 +0100
- Message-id: <[🔎] 20220324132442.xrwtiielft4rexgf@quack3.lan>
- In-reply-to: <[🔎] 20220324075119.1556334-5-hch@lst.de>
- References: <[🔎] 20220324075119.1556334-1-hch@lst.de> <[🔎] 20220324075119.1556334-5-hch@lst.de>
On Thu 24-03-22 08:51:10, Christoph Hellwig wrote:
> Add a helper that returns the openers for a given gendisk to avoid having
> drivers poke into disk->part0 to get at this information in a somewhat
> cumbersome way.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
> ---
> drivers/block/nbd.c | 4 ++--
> drivers/block/zram/zram_drv.c | 4 ++--
> include/linux/blkdev.h | 15 +++++++++++++++
> 3 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 795f65a5c9661..93af7587d5ed6 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1219,7 +1219,7 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
>
> static void nbd_bdev_reset(struct nbd_device *nbd)
> {
> - if (nbd->disk->part0->bd_openers > 1)
> + if (disk_openers(nbd->disk) > 1)
> return;
> set_capacity(nbd->disk, 0);
> }
> @@ -1578,7 +1578,7 @@ static void nbd_release(struct gendisk *disk, fmode_t mode)
> struct nbd_device *nbd = disk->private_data;
>
> if (test_bit(NBD_RT_DISCONNECT_ON_CLOSE, &nbd->config->runtime_flags) &&
> - disk->part0->bd_openers == 0)
> + disk_openers(disk) == 0)
> nbd_disconnect_and_put(nbd);
>
> nbd_config_put(nbd);
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 863606f1722b1..2362385f782a9 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1800,7 +1800,7 @@ static ssize_t reset_store(struct device *dev,
>
> mutex_lock(&disk->open_mutex);
> /* Do not reset an active device or claimed device */
> - if (disk->part0->bd_openers || zram->claim) {
> + if (disk_openers(disk) || zram->claim) {
> mutex_unlock(&disk->open_mutex);
> return -EBUSY;
> }
> @@ -1990,7 +1990,7 @@ static int zram_remove(struct zram *zram)
> bool claimed;
>
> mutex_lock(&zram->disk->open_mutex);
> - if (zram->disk->part0->bd_openers) {
> + if (disk_openers(zram->disk)) {
> mutex_unlock(&zram->disk->open_mutex);
> return -EBUSY;
> }
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index eb27312a1b8f3..9824ebc9b4d31 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -176,6 +176,21 @@ static inline bool disk_live(struct gendisk *disk)
> return !inode_unhashed(disk->part0->bd_inode);
> }
>
> +/**
> + * disk_openers - returns how many openers are there for a disk
> + * @disk: disk to check
> + *
> + * This returns the number of openers for a disk. Note that this value is only
> + * stable if disk->open_mutex is held.
> + *
> + * Note: Due to a quirk in the block layer open code, each open partition is
> + * only counted once even if there are multiple openers.
> + */
> +static inline unsigned int disk_openers(struct gendisk *disk)
> +{
> + return disk->part0->bd_openers;
> +}
> +
> /*
> * The gendisk is refcounted by the part0 block_device, and the bd_device
> * therein is also used for device model presentation in sysfs.
> --
> 2.30.2
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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