Re: [PATCH 15/17] block: call into the file system for ioctl BLKFLSBUF

[Josef Bacik <josef@toxicpanda.com>]

On Fri, Aug 11, 2023 at 12:08:26PM +0200, Christoph Hellwig wrote:
> BLKFLSBUF is a historic ioctl that is called on a file handle to a
> block device and syncs either the file system mounted on that block
> device if there is one, or otherwise the just the data on the block
> device.
> 
> Replace the get_super based syncing with a holder operation to remove
> the last usage of get_super, and to also support syncing the file system
> if the block device is not the main block device stored in s_dev.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  block/bdev.c           | 16 ----------------
>  block/ioctl.c          |  9 ++++++++-
>  fs/super.c             | 13 +++++++++++++
>  include/linux/blkdev.h |  7 +++++--
>  4 files changed, 26 insertions(+), 19 deletions(-)
> 
> diff --git a/block/bdev.c b/block/bdev.c
> index 658d5dd62cac0a..2a035be7f3ee90 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -206,22 +206,6 @@ int sync_blockdev_range(struct block_device *bdev, loff_t lstart, loff_t lend)
>  }
>  EXPORT_SYMBOL(sync_blockdev_range);
>  
> -/*
> - * Write out and wait upon all dirty data associated with this
> - * device.   Filesystem data as well as the underlying block
> - * device.  Takes the superblock lock.
> - */
> -int fsync_bdev(struct block_device *bdev)
> -{
> -	struct super_block *sb = get_super(bdev);
> -	if (sb) {
> -		int res = sync_filesystem(sb);
> -		drop_super(sb);
> -		return res;
> -	}
> -	return sync_blockdev(bdev);
> -}
> -
>  /**
>   * freeze_bdev - lock a filesystem and force it into a consistent state
>   * @bdev:	blockdevice to lock
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 3be11941fb2ddc..648670ddb164a0 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -364,7 +364,14 @@ static int blkdev_flushbuf(struct block_device *bdev, unsigned cmd,
>  {
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EACCES;
> -	fsync_bdev(bdev);
> +
> +	mutex_lock(&bdev->bd_holder_lock);
> +	if (bdev->bd_holder_ops && bdev->bd_holder_ops->sync)
> +		bdev->bd_holder_ops->sync(bdev);
> +	else
> +		sync_blockdev(bdev);
> +	mutex_unlock(&bdev->bd_holder_lock);
> +
>  	invalidate_bdev(bdev);
>  	return 0;
>  }
> diff --git a/fs/super.c b/fs/super.c
> index 94d41040584f7b..714dbae58b5e8e 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -1248,8 +1248,21 @@ static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise)
>  	up_read(&sb->s_umount);
>  }
>  
> +static void fs_bdev_sync(struct block_device *bdev)
> +{
> +	struct super_block *sb = bdev->bd_holder;
> +
> +	lockdep_assert_held(&bdev->bd_holder_lock);
> +
> +	if (!lock_active_super(sb))
> +		return;
> +	sync_filesystem(sb);
> +	up_read(&sb->s_umount);
> +}
> + 

Whitespace error.  Thanks,

Josef