Re: Regression: wrong DIO alignment check with dm-crypt

[Dmitrii Tcvetkov <me@demsh.org>]

On Wed, 2 Nov 2022 14:09:54 -0600
Keith Busch <kbusch@kernel.org> wrote:

> On Wed, Nov 02, 2022 at 08:03:45PM +0300, Dmitrii Tcvetkov wrote:
> > 
> > Applied on top 6.1-rc3, the issue still reproduces.
> 
> Yeah, I see that now. I needed to run a dm-crypt setup to figure out
> how they're actually doing this, so now I have that up and running.
> 
> I think this type of usage will require the dma_alignment to move from
> the request_queue to the queue_limits. Here's that, and I've
> successfully tested this with cryptsetup. I still need more work to
> get mdraid atop that working on my dev machine, but I'll post this
> now since it's looking better:
> 
> ---
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 8bb9eef5310e..e84304959318 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -81,6 +81,7 @@ void blk_set_stacking_limits(struct queue_limits
> *lim) lim->max_dev_sectors = UINT_MAX;
>  	lim->max_write_zeroes_sectors = UINT_MAX;
>  	lim->max_zone_append_sectors = UINT_MAX;
> +	lim->dma_alignment = 511;
>  }
>  EXPORT_SYMBOL(blk_set_stacking_limits);
>  
> @@ -600,6 +601,7 @@ int blk_stack_limits(struct queue_limits *t,
> struct queue_limits *b, 
>  	t->io_min = max(t->io_min, b->io_min);
>  	t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
> +	t->dma_alignment = max(t->dma_alignment, b->dma_alignment);
>  
>  	/* Set non-power-of-2 compatible chunk_sectors boundary */
>  	if (b->chunk_sectors)
> @@ -773,7 +775,7 @@ EXPORT_SYMBOL(blk_queue_virt_boundary);
>   **/
>  void blk_queue_dma_alignment(struct request_queue *q, int mask)
>  {
> -	q->dma_alignment = mask;
> +	q->limits.dma_alignment = mask;
>  }
>  EXPORT_SYMBOL(blk_queue_dma_alignment);
>  
> @@ -795,8 +797,8 @@ void blk_queue_update_dma_alignment(struct
> request_queue *q, int mask) {
>  	BUG_ON(mask > PAGE_SIZE);
>  
> -	if (mask > q->dma_alignment)
> -		q->dma_alignment = mask;
> +	if (mask > q->limits.dma_alignment)
> +		q->limits.dma_alignment = mask;
>  }
>  EXPORT_SYMBOL(blk_queue_update_dma_alignment);
>  
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index 159c6806c19b..2653516bcdef 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -3630,6 +3630,7 @@ static void crypt_io_hints(struct dm_target
> *ti, struct queue_limits *limits) limits->physical_block_size =
>  		max_t(unsigned, limits->physical_block_size,
> cc->sector_size); limits->io_min = max_t(unsigned, limits->io_min,
> cc->sector_size);
> +	limits->dma_alignment = limits->logical_block_size - 1;
>  }
>  
>  static struct target_type crypt_target = {
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 854b4745cdd1..69ee5ea29e2f 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -310,6 +310,13 @@ struct queue_limits {
>  	unsigned char		discard_misaligned;
>  	unsigned char		raid_partial_stripes_expensive;
>  	enum blk_zoned_model	zoned;
> +
> +	/*
> +	 * Drivers that set dma_alignment to less than 511 must be
> prepared to
> +	 * handle individual bvec's that are not a multiple of a
> SECTOR_SIZE
> +	 * due to possible offsets.
> +	 */
> +	unsigned int		dma_alignment;
>  };
>  
>  typedef int (*report_zones_cb)(struct blk_zone *zone, unsigned int
> idx, @@ -455,12 +462,6 @@ struct request_queue {
>  	unsigned long		nr_requests;	/* Max # of
> requests */ 
>  	unsigned int		dma_pad_mask;
> -	/*
> -	 * Drivers that set dma_alignment to less than 511 must be
> prepared to
> -	 * handle individual bvec's that are not a multiple of a
> SECTOR_SIZE
> -	 * due to possible offsets.
> -	 */
> -	unsigned int		dma_alignment;
>  
>  #ifdef CONFIG_BLK_INLINE_ENCRYPTION
>  	struct blk_crypto_profile *crypto_profile;
> @@ -1318,7 +1319,7 @@ static inline sector_t bdev_zone_sectors(struct
> block_device *bdev) 
>  static inline int queue_dma_alignment(const struct request_queue *q)
>  {
> -	return q ? q->dma_alignment : 511;
> +	return q ? q->limits.dma_alignment : 511;
>  }
>  
>  static inline unsigned int bdev_dma_alignment(struct block_device
> *bdev) --

With this patch the issue doesn't reproduce.