Re: [RFC v4 linux-next 18/19] scsi: factor out a helper bdev_read_folio() from scsi_bios_ptable()

[Jan Kara <jack@suse.cz>]

On Thu 22-02-24 20:45:54, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> scsi_bios_ptable() is reading without opening disk as file, factor out
> a helper to read into block device page cache to prevent access bd_inode
> directly from scsi.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Looks good to me. Either before or after split feel free to add:

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

								Honza

> ---
>  block/bdev.c           | 19 +++++++++++++++++++
>  drivers/scsi/scsicam.c |  3 +--
>  include/linux/blkdev.h |  1 +
>  3 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/block/bdev.c b/block/bdev.c
> index 60a1479eae83..b7af04d34af2 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -1211,6 +1211,25 @@ unsigned int block_size(struct block_device *bdev)
>  }
>  EXPORT_SYMBOL_GPL(block_size);
>  
> +/**
> + * bdev_read_folio - Read into block device page cache.
> + * @bdev: the block device which holds the cache to read.
> + * @pos: the offset that allocated folio will contain.
> + *
> + * Read one page into the block device page cache. If it succeeds, the folio
> + * returned will contain @pos;
> + *
> + * This is only used for scsi_bios_ptable(), the bdev is not opened as files.
> + *
> + * Return: Uptodate folio on success, ERR_PTR() on failure.
> + */
> +struct folio *bdev_read_folio(struct block_device *bdev, loff_t pos)
> +{
> +	return mapping_read_folio_gfp(bdev_mapping(bdev),
> +				      pos >> PAGE_SHIFT, GFP_KERNEL);
> +}
> +EXPORT_SYMBOL_GPL(bdev_read_folio);
> +
>  static int __init setup_bdev_allow_write_mounted(char *str)
>  {
>  	if (kstrtobool(str, &bdev_allow_write_mounted))
> diff --git a/drivers/scsi/scsicam.c b/drivers/scsi/scsicam.c
> index e2c7d8ef205f..1c99b964a0eb 100644
> --- a/drivers/scsi/scsicam.c
> +++ b/drivers/scsi/scsicam.c
> @@ -32,11 +32,10 @@
>   */
>  unsigned char *scsi_bios_ptable(struct block_device *dev)
>  {
> -	struct address_space *mapping = bdev_whole(dev)->bd_inode->i_mapping;
>  	unsigned char *res = NULL;
>  	struct folio *folio;
>  
> -	folio = read_mapping_folio(mapping, 0, NULL);
> +	folio = bdev_read_folio(bdev_whole(dev), 0);
>  	if (IS_ERR(folio))
>  		return NULL;
>  
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index c510f334c84f..3fb02e3a527a 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1514,6 +1514,7 @@ struct file *bdev_file_open_by_path(const char *path, blk_mode_t mode,
>  int bd_prepare_to_claim(struct block_device *bdev, void *holder,
>  		const struct blk_holder_ops *hops);
>  void bd_abort_claiming(struct block_device *bdev, void *holder);
> +struct folio *bdev_read_folio(struct block_device *bdev, loff_t pos);
>  
>  /* just for blk-cgroup, don't use elsewhere */
>  struct block_device *blkdev_get_no_open(dev_t dev);
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR