Re: [PATCH 5/5] block: remove (__)blkdev_reread_part as an exported API

Jan Kara
2019-11-14T14:24:08Z

On Wed 06-11-19 16:14:39, Christoph Hellwig wrote:
> In general drivers should never mess with partition tables directly.
> Unfortunately s390 and loop do for somewhat historic reasons, but they
> can use bdev_disk_changed directly instead when we export it as they
> satisfy the sanity checks we have in __blkdev_reread_part.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> block/ioctl.c | 35 +++++----------------------------
> drivers/block/loop.c | 13 +++++++-----
> drivers/s390/block/dasd_genhd.c | 4 +++-
> fs/block_dev.c | 7 +++++++
> include/linux/fs.h | 2 --
> 5 files changed, 23 insertions(+), 38 deletions(-)
>
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 52380c337078..2ed907ef0f01 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -155,46 +155,21 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
> }
> }
>
> -/*
> - * This is an exported API for the block driver, and will not
> - * acquire bd_mutex. This API should be used in case that
> - * caller has held bd_mutex already.
> - */
> -int __blkdev_reread_part(struct block_device *bdev)
> +static int blkdev_reread_part(struct block_device *bdev)
> {
> + int ret;
> +
> if (!disk_part_scan_enabled(bdev->bd_disk) || bdev != bdev->bd_contains)
> return -EINVAL;
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
>
> - lockdep_assert_held(&bdev->bd_mutex);
> -
> - return bdev_disk_changed(bdev, false);
> -}
> -EXPORT_SYMBOL(__blkdev_reread_part);
> -
> -/*
> - * This is an exported API for the block driver, and will
> - * try to acquire bd_mutex. If bd_mutex has been held already
> - * in current context, please call __blkdev_reread_part().
> - *
> - * Make sure the held locks in current context aren't required
> - * in open()/close() handler and I/O path for avoiding ABBA deadlock:
> - * - bd_mutex is held before calling block driver's open/close
> - * handler
> - * - reading partition table may submit I/O to the block device
> - */
> -int blkdev_reread_part(struct block_device *bdev)
> -{
> - int res;
> -
> mutex_lock(&bdev->bd_mutex);
> - res = __blkdev_reread_part(bdev);
> + ret = bdev_disk_changed(bdev, false);
> mutex_unlock(&bdev->bd_mutex);
>
> - return res;
> + return ret;
> }
> -EXPORT_SYMBOL(blkdev_reread_part);
>
> static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
> unsigned long arg, unsigned long flags)
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index f6f77eaa7217..64b16abee280 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -630,7 +630,9 @@ static void loop_reread_partitions(struct loop_device *lo,
> {
> int rc;
>
> - rc = blkdev_reread_part(bdev);
> + mutex_lock(&bdev->bd_mutex);
> + rc = bdev_disk_changed(bdev, false);
> + mutex_unlock(&bdev->bd_mutex);
> if (rc)
> pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
> __func__, lo->lo_number, lo->lo_file_name, rc);
> @@ -1154,10 +1156,11 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
> * must be at least one and it can only become zero when the
> * current holder is released.
> */
> - if (release)
> - err = __blkdev_reread_part(bdev);
> - else
> - err = blkdev_reread_part(bdev);
> + if (!release)
> + mutex_lock(&bdev->bd_mutex);
> + err = bdev_disk_changed(bdev, false);
> + if (!release)
> + mutex_unlock(&bdev->bd_mutex);
> if (err)
> pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
> __func__, lo_number, err);
> diff --git a/drivers/s390/block/dasd_genhd.c b/drivers/s390/block/dasd_genhd.c
> index 5542d9eadfe0..7d079154f849 100644
> --- a/drivers/s390/block/dasd_genhd.c
> +++ b/drivers/s390/block/dasd_genhd.c
> @@ -116,7 +116,9 @@ int dasd_scan_partitions(struct dasd_block *block)
> return -ENODEV;
> }
>
> - rc = blkdev_reread_part(bdev);
> + mutex_lock(&bdev->bd_mutex);
> + rc = bdev_disk_changed(bdev, false);
> + mutex_unlock(&bdev->bd_mutex);
> if (rc)
> DBF_DEV_EVENT(DBF_ERR, block->base,
> "scan partitions error, rc %d", rc);
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index ae16466a67f7..9558a2f064b1 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1513,6 +1513,8 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
> struct gendisk *disk = bdev->bd_disk;
> int ret;
>
> + lockdep_assert_held(&bdev->bd_mutex);
> +
> rescan:
> ret = blk_drop_partitions(disk, bdev);
> if (ret)
> @@ -1540,6 +1542,11 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
>
> return ret;
> }
> +/*
> + * Only exported for for loop and dasd for historic reasons. Don't use in new
> + * code!
> + */
> +EXPORT_SYMBOL_GPL(bdev_disk_changed);
>
> /*
> * bd_mutex locking:
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index d233dd661df7..ae6c5c37f3ae 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2632,8 +2632,6 @@ extern void bd_finish_claiming(struct block_device *bdev,
> extern void bd_abort_claiming(struct block_device *bdev,
> struct block_device *whole, void *holder);
> extern void blkdev_put(struct block_device *bdev, fmode_t mode);
> -extern int __blkdev_reread_part(struct block_device *bdev);
> -extern int blkdev_reread_part(struct block_device *bdev);
>
> #ifdef CONFIG_SYSFS
> extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
> --
> 2.20.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR