[PATCH 10/26] xen-blkfront: don't disable cache flushes when they fail

[Damien Le Moal]

On 6/11/24 2:19 PM, Christoph Hellwig wrote:
> blkfront always had a robust negotiation protocol for detecting a write
> cache.  Stop simply disabling cache flushes when they fail as that is
> a grave error.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Looks good to me but maybe mention that removal of xlvbd_flush() as well ?
And it feels like the "stop disabling cache flushes when they fail" part should
be a fix patch sent separately...

Anyway, for both parts, feel free to add:

Reviewed-by: Damien Le Moal <dlemoal at kernel.org>

> ---
>  drivers/block/xen-blkfront.c | 29 +++++++++--------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 9b4ec3e4908cce..9794ac2d3299d1 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -982,18 +982,6 @@ static const char *flush_info(struct blkfront_info *info)
>  		return "barrier or flush: disabled;";
>  }
>  
> -static void xlvbd_flush(struct blkfront_info *info)
> -{
> -	blk_queue_write_cache(info->rq, info->feature_flush ? true : false,
> -			      info->feature_fua ? true : false);
> -	pr_info("blkfront: %s: %s %s %s %s %s %s %s\n",
> -		info->gd->disk_name, flush_info(info),
> -		"persistent grants:", info->feature_persistent ?
> -		"enabled;" : "disabled;", "indirect descriptors:",
> -		info->max_indirect_segments ? "enabled;" : "disabled;",
> -		"bounce buffer:", info->bounce ? "enabled" : "disabled;");
> -}
> -
>  static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
>  {
>  	int major;
> @@ -1162,7 +1150,15 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
>  	info->sector_size = sector_size;
>  	info->physical_sector_size = physical_sector_size;
>  
> -	xlvbd_flush(info);
> +	blk_queue_write_cache(info->rq, info->feature_flush ? true : false,
> +			      info->feature_fua ? true : false);
> +
> +	pr_info("blkfront: %s: %s %s %s %s %s %s %s\n",
> +		info->gd->disk_name, flush_info(info),
> +		"persistent grants:", info->feature_persistent ?
> +		"enabled;" : "disabled;", "indirect descriptors:",
> +		info->max_indirect_segments ? "enabled;" : "disabled;",
> +		"bounce buffer:", info->bounce ? "enabled" : "disabled;");
>  
>  	if (info->vdisk_info & VDISK_READONLY)
>  		set_disk_ro(gd, 1);
> @@ -1622,13 +1618,6 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
>  				       info->gd->disk_name, op_name(bret.operation));
>  				blkif_req(req)->error = BLK_STS_NOTSUPP;
>  			}
> -			if (unlikely(blkif_req(req)->error)) {
> -				if (blkif_req(req)->error == BLK_STS_NOTSUPP)
> -					blkif_req(req)->error = BLK_STS_OK;
> -				info->feature_fua = 0;
> -				info->feature_flush = 0;
> -				xlvbd_flush(info);
> -			}
>  			fallthrough;
>  		case BLKIF_OP_READ:
>  		case BLKIF_OP_WRITE:

-- 
Damien Le Moal
Western Digital Research