[PATCH 4/7] block: reparse partition table when necessary

[Marco Felsch]

On 24-02-15, Sascha Hauer wrote:
> Call reparse_partition_table() when the partition table may have
> changed. We detect this by recording if the block device has been
> written to in the area where the partition table is.
> 
> Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> ---
>  common/block.c  | 30 ++++++++++++++++++++++++++++--
>  include/block.h |  2 ++
>  2 files changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/common/block.c b/common/block.c
> index 3a4a9fb731..007c8bed12 100644
> --- a/common/block.c
> +++ b/common/block.c
> @@ -284,6 +284,17 @@ static ssize_t block_op_write(struct cdev *cdev, const void *buf, size_t count,
>  	blkcnt_t blocks;
>  	int ret;
>  
> +	/*
> +	 * When the offset that is written to is within the first two
> +	 * LBAs then the partition table has changed, reparse the partition
> +	 * table at close time in this case. A GPT covers more space than
> +	 * only the first two LBAs, but a CRC of the remaining pieces is
> +	 * written to LBA1, so LBA1 must change as well when the partioning
> +	 * is changed.
> +	 */
> +	if (offset < 2 * SECTOR_SIZE)
> +		blk->need_reparse = true;
> +
>  	if (offset & mask) {
>  		size_t now = BLOCKSIZE(blk) - (offset & mask);
>  		void *iobuf = block_get(blk, block);
> @@ -335,13 +346,28 @@ static ssize_t block_op_write(struct cdev *cdev, const void *buf, size_t count,
>  static int block_op_flush(struct cdev *cdev)
>  {
>  	struct block_device *blk = cdev->priv;
> +	int ret;
>  
>  	blk->discard_start = blk->discard_size = 0;
>  
> -	return writebuffer_flush(blk);
> +	ret = writebuffer_flush(blk);
> +
> +	return ret;

This change is not required or do I miss something?

Regards,
  Marco

>  }
>  
> -static int block_op_close(struct cdev *cdev) __alias(block_op_flush);
> +static int block_op_close(struct cdev *cdev)
> +{
> +	struct block_device *blk = cdev->priv;
> +
> +	block_op_flush(cdev);
> +
> +	if (blk->need_reparse) {
> +		reparse_partition_table(blk);
> +		blk->need_reparse = false;
> +	}
> +
> +	return 0;
> +}
>  
>  static int block_op_discard_range(struct cdev *cdev, loff_t count, loff_t offset)
>  {
> diff --git a/include/block.h b/include/block.h
> index 44037bd74c..aaaa97400f 100644
> --- a/include/block.h
> +++ b/include/block.h
> @@ -33,6 +33,8 @@ struct block_device {
>  	struct list_head idle_blocks;
>  
>  	struct cdev cdev;
> +
> +	bool need_reparse;
>  };
>  
>  extern struct list_head block_device_list;
> -- 
> 2.39.2
> 
> 
>