Subject: Re: [PATCH 41/42] block: do not use REQ_FLUSH for tracking flush
 support
To: mchristi@redhat.com, linux-f2fs-devel@lists.sourceforge.net,
        linux-ext4@vger.kernel.org, konrad.wilk@oracle.com,
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        linux-btrfs@vger.kernel.org, osd-dev@open-osd.org, xfs@oss.sgi.com,
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References: <1460716802-2294-1-git-send-email-mchristi@redhat.com>
 <1460716802-2294-42-git-send-email-mchristi@redhat.com>
From: Juergen Gross <kernel@pfupf.net>
Message-ID: <5710C77F.2000405@pfupf.net>
Date: Fri, 15 Apr 2016 12:50:39 +0200
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On 15/04/16 12:40, mchristi@redhat.com wrote:
> From: Mike Christie <mchristi@redhat.com>
> 
> The last patch added a REQ_OP_FLUSH for request_fn drivers
> and the next patch renames REQ_FLUSH to REQ_PREFLUSH which
> will be used by file systems and make_request_fn drivers so
> they can send a write/flush combo.
> 
> This patch drops xen's use of REQ_FLUSH to track if it supports
> REQ_OP_FLUSH requests, so REQ_FLUSH can be deleted.
> 
> v6:
> - Dropped parts of patch handled by Jens's QUEUE_FLAG_WC/FUA
> patches and modified patch to check feature_flush/fua bits.
> 
> Signed-off-by: Mike Christie <mchristi@redhat.com>
> Reviewed-by: Hannes Reinecke <hare@suse.com>
> ---
>  drivers/block/xen-blkfront.c | 47 ++++++++++++++++++++++----------------------
>  1 file changed, 24 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index f01691a..d6429e7 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c

...

> @@ -985,24 +981,22 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
>  	return 0;
>  }
>  
> -static const char *flush_info(unsigned int feature_flush)
> +static const char *flush_info(struct blkfront_info *info)
>  {
> -	switch (feature_flush & ((REQ_FLUSH | REQ_FUA))) {
> -	case REQ_FLUSH|REQ_FUA:
> +	if (info->feature_flush && info->feature_fua)
>  		return "barrier: enabled;";
> -	case REQ_FLUSH:
> +	else if (info->feature_fua)

Shouldn't this test feature_flush?

>  		return "flush diskcache: enabled;";
> -	default:
> +	else
>  		return "barrier or flush: disabled;";
> -	}
>  }
>  
>  static void xlvbd_flush(struct blkfront_info *info)
>  {
> -	blk_queue_write_cache(info->rq, info->feature_flush & REQ_FLUSH,
> -				info->feature_flush & REQ_FUA);
> +	blk_queue_write_cache(info->rq, info->feature_flush ? true : false,
> +			      info->feature_flush ? true : false);

And here the second test should be feature_fua?

>  	pr_info("blkfront: %s: %s %s %s %s %s\n",
> -		info->gd->disk_name, flush_info(info->feature_flush),
> +		info->gd->disk_name, flush_info(info),
>  		"persistent grants:", info->feature_persistent ?
>  		"enabled;" : "disabled;", "indirect descriptors:",
>  		info->max_indirect_segments ? "enabled;" : "disabled;");


Juergen