[PATCH] xen/blkfront: remove redundant flush_op

[PATCH] xen/blkfront: remove redundant flush_op

[Vitaly Kuznetsov]

flush_op is unambiguously defined by feature_flush:
    REQ_FUA | REQ_FLUSH -> BLKIF_OP_WRITE_BARRIER
    REQ_FLUSH -> BLKIF_OP_FLUSH_DISKCACHE
    0 -> 0
and thus can be removed. This is just a cleanup.

The patch was suggested by Boris Ostrovsky.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
The patch is supposed to be applied after "xen/blkfront: improve protection
against issuing unsupported REQ_FUA".
---
 drivers/block/xen-blkfront.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 2e6c103..d1ee233 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -126,7 +126,6 @@ struct blkfront_info
 	unsigned int persistent_gnts_c;
 	unsigned long shadow_free;
 	unsigned int feature_flush;
-	unsigned int flush_op;
 	unsigned int feature_discard:1;
 	unsigned int feature_secdiscard:1;
 	unsigned int discard_granularity;
@@ -479,7 +478,14 @@ static int blkif_queue_request(struct request *req)
 				 * way.  (It's also a FLUSH+FUA, since it is
 				 * guaranteed ordered WRT previous writes.)
 				 */
-				ring_req->operation = info->flush_op;
+				if (unlikely(info->feature_flush & REQ_FUA))
+					ring_req->operation =
+						BLKIF_OP_WRITE_BARRIER;
+				else if (likely(info->feature_flush))
+					ring_req->operation =
+						BLKIF_OP_FLUSH_DISKCACHE;
+				else
+					ring_req->operation = 0;
 			}
 			ring_req->u.rw.nr_segments = nseg;
 		}
@@ -691,8 +697,8 @@ static void xlvbd_flush(struct blkfront_info *info)
 	blk_queue_flush(info->rq, info->feature_flush);
 	printk(KERN_INFO "blkfront: %s: %s: %s %s %s %s %s\n",
 	       info->gd->disk_name,
-	       info->flush_op == BLKIF_OP_WRITE_BARRIER ?
-		"barrier" : (info->flush_op == BLKIF_OP_FLUSH_DISKCACHE ?
+	       info->feature_flush == (REQ_FLUSH | REQ_FUA) ?
+		"barrier" : (info->feature_flush == REQ_FLUSH ?
 		"flush diskcache" : "barrier or flush"),
 	       info->feature_flush ? "enabled;" : "disabled;",
 	       "persistent grants:",
@@ -1190,7 +1196,6 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 				if (error == -EOPNOTSUPP)
 					error = 0;
 				info->feature_flush = 0;
-				info->flush_op = 0;
 				xlvbd_flush(info);
 			}
 			/* fall through */
@@ -1810,7 +1815,6 @@ static void blkfront_connect(struct blkfront_info *info)
 		physical_sector_size = sector_size;
 
 	info->feature_flush = 0;
-	info->flush_op = 0;
 
 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
 			    "feature-barrier", "%d", &barrier,
@@ -1823,10 +1827,8 @@ static void blkfront_connect(struct blkfront_info *info)
 	 *
 	 * If there are barriers, then we use flush.
 	 */
-	if (!err && barrier) {
+	if (!err && barrier)
 		info->feature_flush = REQ_FLUSH | REQ_FUA;
-		info->flush_op = BLKIF_OP_WRITE_BARRIER;
-	}
 	/*
 	 * And if there is "feature-flush-cache" use that above
 	 * barriers.
@@ -1835,10 +1837,8 @@ static void blkfront_connect(struct blkfront_info *info)
 			    "feature-flush-cache", "%d", &flush,
 			    NULL);
 
-	if (!err && flush) {
+	if (!err && flush)
 		info->feature_flush = REQ_FLUSH;
-		info->flush_op = BLKIF_OP_FLUSH_DISKCACHE;
-	}
 
 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
 			    "feature-discard", "%d", &discard,
-- 
1.9.3

Re: [PATCH] xen/blkfront: remove redundant flush_op

[Boris Ostrovsky]

On 12/08/2014 09:17 AM, Vitaly Kuznetsov wrote:
> flush_op is unambiguously defined by feature_flush:
>      REQ_FUA | REQ_FLUSH -> BLKIF_OP_WRITE_BARRIER
>      REQ_FLUSH -> BLKIF_OP_FLUSH_DISKCACHE
>      0 -> 0
> and thus can be removed. This is just a cleanup.
>
> The patch was suggested by Boris Ostrovsky.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> The patch is supposed to be applied after "xen/blkfront: improve protection
> against issuing unsupported REQ_FUA".
> ---
>   drivers/block/xen-blkfront.c | 24 ++++++++++++------------
>   1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 2e6c103..d1ee233 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -126,7 +126,6 @@ struct blkfront_info
>   	unsigned int persistent_gnts_c;
>   	unsigned long shadow_free;
>   	unsigned int feature_flush;
> -	unsigned int flush_op;
>   	unsigned int feature_discard:1;
>   	unsigned int feature_secdiscard:1;
>   	unsigned int discard_granularity;
> @@ -479,7 +478,14 @@ static int blkif_queue_request(struct request *req)
>   				 * way.  (It's also a FLUSH+FUA, since it is
>   				 * guaranteed ordered WRT previous writes.)
>   				 */
> -				ring_req->operation = info->flush_op;
> +				if (unlikely(info->feature_flush & REQ_FUA))
> +					ring_req->operation =
> +						BLKIF_OP_WRITE_BARRIER;
> +				else if (likely(info->feature_flush))
> +					ring_req->operation =
> +						BLKIF_OP_FLUSH_DISKCACHE;

To better future-proof it against new flags maybe something like

     switch ( info->feature_flush & (REQ_FLUSH|REQ_FUA) ) {
            case REQ_FLUSH|REQ_FUA: ...
            case REQ_FLUSH: ...
            default: ...

or the if/else equivalent?


> +				else
> +					ring_req->operation = 0;
>   			}
>   			ring_req->u.rw.nr_segments = nseg;
>   		}
> @@ -691,8 +697,8 @@ static void xlvbd_flush(struct blkfront_info *info)
>   	blk_queue_flush(info->rq, info->feature_flush);
>   	printk(KERN_INFO "blkfront: %s: %s: %s %s %s %s %s\n",
>   	       info->gd->disk_name,
> -	       info->flush_op == BLKIF_OP_WRITE_BARRIER ?
> -		"barrier" : (info->flush_op == BLKIF_OP_FLUSH_DISKCACHE ?
> +	       info->feature_flush == (REQ_FLUSH | REQ_FUA) ?
> +		"barrier" : (info->feature_flush == REQ_FLUSH ?

And something similar here?

Thanks.
-boris


>   		"flush diskcache" : "barrier or flush"),
>   	       info->feature_flush ? "enabled;" : "disabled;",
>   	       "persistent grants:",
> @@ -1190,7 +1196,6 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
>   				if (error == -EOPNOTSUPP)
>   					error = 0;
>   				info->feature_flush = 0;
> -				info->flush_op = 0;
>   				xlvbd_flush(info);
>   			}
>   			/* fall through */
> @@ -1810,7 +1815,6 @@ static void blkfront_connect(struct blkfront_info *info)
>   		physical_sector_size = sector_size;
>   
>   	info->feature_flush = 0;
> -	info->flush_op = 0;
>   
>   	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
>   			    "feature-barrier", "%d", &barrier,
> @@ -1823,10 +1827,8 @@ static void blkfront_connect(struct blkfront_info *info)
>   	 *
>   	 * If there are barriers, then we use flush.
>   	 */
> -	if (!err && barrier) {
> +	if (!err && barrier)
>   		info->feature_flush = REQ_FLUSH | REQ_FUA;
> -		info->flush_op = BLKIF_OP_WRITE_BARRIER;
> -	}
>   	/*
>   	 * And if there is "feature-flush-cache" use that above
>   	 * barriers.
> @@ -1835,10 +1837,8 @@ static void blkfront_connect(struct blkfront_info *info)
>   			    "feature-flush-cache", "%d", &flush,
>   			    NULL);
>   
> -	if (!err && flush) {
> +	if (!err && flush)
>   		info->feature_flush = REQ_FLUSH;
> -		info->flush_op = BLKIF_OP_FLUSH_DISKCACHE;
> -	}
>   
>   	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
>   			    "feature-discard", "%d", &discard,

[PATCH v2] xen/blkfront: remove redundant flush_op

[Vitaly Kuznetsov]

flush_op is unambiguously defined by feature_flush:
    REQ_FUA | REQ_FLUSH -> BLKIF_OP_WRITE_BARRIER
    REQ_FLUSH -> BLKIF_OP_FLUSH_DISKCACHE
    0 -> 0
and thus can be removed. This is just a cleanup.

The patch was suggested by Boris Ostrovsky.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
Changes from v1:
   Future-proof feature_flush against new flags [Boris Ostrovsky].

The patch is supposed to be applied after "xen/blkfront: improve protection
against issuing unsupported REQ_FUA".
---
 drivers/block/xen-blkfront.c | 51 +++++++++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 2e6c103..2236c6f 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -126,7 +126,6 @@ struct blkfront_info
 	unsigned int persistent_gnts_c;
 	unsigned long shadow_free;
 	unsigned int feature_flush;
-	unsigned int flush_op;
 	unsigned int feature_discard:1;
 	unsigned int feature_secdiscard:1;
 	unsigned int discard_granularity;
@@ -479,7 +478,19 @@ static int blkif_queue_request(struct request *req)
 				 * way.  (It's also a FLUSH+FUA, since it is
 				 * guaranteed ordered WRT previous writes.)
 				 */
-				ring_req->operation = info->flush_op;
+				switch (info->feature_flush &
+					((REQ_FLUSH|REQ_FUA))) {
+				case REQ_FLUSH|REQ_FUA:
+					ring_req->operation =
+						BLKIF_OP_WRITE_BARRIER;
+					break;
+				case REQ_FLUSH:
+					ring_req->operation =
+						BLKIF_OP_FLUSH_DISKCACHE;
+					break;
+				default:
+					ring_req->operation = 0;
+				}
 			}
 			ring_req->u.rw.nr_segments = nseg;
 		}
@@ -685,20 +696,26 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
 	return 0;
 }
 
+static const char *flush_info(unsigned int feature_flush)
+{
+	switch (feature_flush & ((REQ_FLUSH | REQ_FUA))) {
+	case REQ_FLUSH|REQ_FUA:
+		return "barrier: enabled;";
+	case REQ_FLUSH:
+		return "flush diskcache: enabled;";
+	default:
+		return "barrier or flush: disabled;";
+	}
+}
 
 static void xlvbd_flush(struct blkfront_info *info)
 {
 	blk_queue_flush(info->rq, info->feature_flush);
-	printk(KERN_INFO "blkfront: %s: %s: %s %s %s %s %s\n",
-	       info->gd->disk_name,
-	       info->flush_op == BLKIF_OP_WRITE_BARRIER ?
-		"barrier" : (info->flush_op == BLKIF_OP_FLUSH_DISKCACHE ?
-		"flush diskcache" : "barrier or flush"),
-	       info->feature_flush ? "enabled;" : "disabled;",
-	       "persistent grants:",
-	       info->feature_persistent ? "enabled;" : "disabled;",
-	       "indirect descriptors:",
-	       info->max_indirect_segments ? "enabled;" : "disabled;");
+	pr_info("blkfront: %s: %s %s %s %s %s\n",
+		info->gd->disk_name, flush_info(info->feature_flush),
+		"persistent grants:", info->feature_persistent ?
+		"enabled;" : "disabled;", "indirect descriptors:",
+		info->max_indirect_segments ? "enabled;" : "disabled;");
 }
 
 static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
@@ -1190,7 +1207,6 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 				if (error == -EOPNOTSUPP)
 					error = 0;
 				info->feature_flush = 0;
-				info->flush_op = 0;
 				xlvbd_flush(info);
 			}
 			/* fall through */
@@ -1810,7 +1826,6 @@ static void blkfront_connect(struct blkfront_info *info)
 		physical_sector_size = sector_size;
 
 	info->feature_flush = 0;
-	info->flush_op = 0;
 
 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
 			    "feature-barrier", "%d", &barrier,
@@ -1823,10 +1838,8 @@ static void blkfront_connect(struct blkfront_info *info)
 	 *
 	 * If there are barriers, then we use flush.
 	 */
-	if (!err && barrier) {
+	if (!err && barrier)
 		info->feature_flush = REQ_FLUSH | REQ_FUA;
-		info->flush_op = BLKIF_OP_WRITE_BARRIER;
-	}
 	/*
 	 * And if there is "feature-flush-cache" use that above
 	 * barriers.
@@ -1835,10 +1848,8 @@ static void blkfront_connect(struct blkfront_info *info)
 			    "feature-flush-cache", "%d", &flush,
 			    NULL);
 
-	if (!err && flush) {
+	if (!err && flush)
 		info->feature_flush = REQ_FLUSH;
-		info->flush_op = BLKIF_OP_FLUSH_DISKCACHE;
-	}
 
 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
 			    "feature-discard", "%d", &discard,
-- 
1.9.3

Re: [PATCH v2] xen/blkfront: remove redundant flush_op

[Boris Ostrovsky]

On 12/09/2014 09:25 AM, Vitaly Kuznetsov wrote:
> flush_op is unambiguously defined by feature_flush:
>      REQ_FUA | REQ_FLUSH -> BLKIF_OP_WRITE_BARRIER
>      REQ_FLUSH -> BLKIF_OP_FLUSH_DISKCACHE
>      0 -> 0
> and thus can be removed. This is just a cleanup.
>
> The patch was suggested by Boris Ostrovsky.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>


> ---
> Changes from v1:
>     Future-proof feature_flush against new flags [Boris Ostrovsky].
>
> The patch is supposed to be applied after "xen/blkfront: improve protection
> against issuing unsupported REQ_FUA".
> ---
>   drivers/block/xen-blkfront.c | 51 +++++++++++++++++++++++++++-----------------
>   1 file changed, 31 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 2e6c103..2236c6f 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -126,7 +126,6 @@ struct blkfront_info
>   	unsigned int persistent_gnts_c;
>   	unsigned long shadow_free;
>   	unsigned int feature_flush;
> -	unsigned int flush_op;
>   	unsigned int feature_discard:1;
>   	unsigned int feature_secdiscard:1;
>   	unsigned int discard_granularity;
> @@ -479,7 +478,19 @@ static int blkif_queue_request(struct request *req)
>   				 * way.  (It's also a FLUSH+FUA, since it is
>   				 * guaranteed ordered WRT previous writes.)
>   				 */
> -				ring_req->operation = info->flush_op;
> +				switch (info->feature_flush &
> +					((REQ_FLUSH|REQ_FUA))) {
> +				case REQ_FLUSH|REQ_FUA:
> +					ring_req->operation =
> +						BLKIF_OP_WRITE_BARRIER;
> +					break;
> +				case REQ_FLUSH:
> +					ring_req->operation =
> +						BLKIF_OP_FLUSH_DISKCACHE;
> +					break;
> +				default:
> +					ring_req->operation = 0;
> +				}
>   			}
>   			ring_req->u.rw.nr_segments = nseg;
>   		}
> @@ -685,20 +696,26 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
>   	return 0;
>   }
>   
> +static const char *flush_info(unsigned int feature_flush)
> +{
> +	switch (feature_flush & ((REQ_FLUSH | REQ_FUA))) {
> +	case REQ_FLUSH|REQ_FUA:
> +		return "barrier: enabled;";
> +	case REQ_FLUSH:
> +		return "flush diskcache: enabled;";
> +	default:
> +		return "barrier or flush: disabled;";
> +	}
> +}
>   
>   static void xlvbd_flush(struct blkfront_info *info)
>   {
>   	blk_queue_flush(info->rq, info->feature_flush);
> -	printk(KERN_INFO "blkfront: %s: %s: %s %s %s %s %s\n",
> -	       info->gd->disk_name,
> -	       info->flush_op == BLKIF_OP_WRITE_BARRIER ?
> -		"barrier" : (info->flush_op == BLKIF_OP_FLUSH_DISKCACHE ?
> -		"flush diskcache" : "barrier or flush"),
> -	       info->feature_flush ? "enabled;" : "disabled;",
> -	       "persistent grants:",
> -	       info->feature_persistent ? "enabled;" : "disabled;",
> -	       "indirect descriptors:",
> -	       info->max_indirect_segments ? "enabled;" : "disabled;");
> +	pr_info("blkfront: %s: %s %s %s %s %s\n",
> +		info->gd->disk_name, flush_info(info->feature_flush),
> +		"persistent grants:", info->feature_persistent ?
> +		"enabled;" : "disabled;", "indirect descriptors:",
> +		info->max_indirect_segments ? "enabled;" : "disabled;");
>   }
>   
>   static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
> @@ -1190,7 +1207,6 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
>   				if (error == -EOPNOTSUPP)
>   					error = 0;
>   				info->feature_flush = 0;
> -				info->flush_op = 0;
>   				xlvbd_flush(info);
>   			}
>   			/* fall through */
> @@ -1810,7 +1826,6 @@ static void blkfront_connect(struct blkfront_info *info)
>   		physical_sector_size = sector_size;
>   
>   	info->feature_flush = 0;
> -	info->flush_op = 0;
>   
>   	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
>   			    "feature-barrier", "%d", &barrier,
> @@ -1823,10 +1838,8 @@ static void blkfront_connect(struct blkfront_info *info)
>   	 *
>   	 * If there are barriers, then we use flush.
>   	 */
> -	if (!err && barrier) {
> +	if (!err && barrier)
>   		info->feature_flush = REQ_FLUSH | REQ_FUA;
> -		info->flush_op = BLKIF_OP_WRITE_BARRIER;
> -	}
>   	/*
>   	 * And if there is "feature-flush-cache" use that above
>   	 * barriers.
> @@ -1835,10 +1848,8 @@ static void blkfront_connect(struct blkfront_info *info)
>   			    "feature-flush-cache", "%d", &flush,
>   			    NULL);
>   
> -	if (!err && flush) {
> +	if (!err && flush)
>   		info->feature_flush = REQ_FLUSH;
> -		info->flush_op = BLKIF_OP_FLUSH_DISKCACHE;
> -	}
>   
>   	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
>   			    "feature-discard", "%d", &discard,

Re: [PATCH v2] xen/blkfront: remove redundant flush_op

[Konrad Rzeszutek Wilk]

On Tue, Dec 09, 2014 at 03:56:46PM -0500, Boris Ostrovsky wrote:
> On 12/09/2014 09:25 AM, Vitaly Kuznetsov wrote:
> >flush_op is unambiguously defined by feature_flush:
> >     REQ_FUA | REQ_FLUSH -> BLKIF_OP_WRITE_BARRIER
> >     REQ_FLUSH -> BLKIF_OP_FLUSH_DISKCACHE
> >     0 -> 0
> >and thus can be removed. This is just a cleanup.
> >
> >The patch was suggested by Boris Ostrovsky.
> >
> >Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> 
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Thank you.

I am testing this and the     xen/blkfront: improve protection against issuing unsupported REQ_FUA
right now for 3.19

> 
> 
> >---
> >Changes from v1:
> >    Future-proof feature_flush against new flags [Boris Ostrovsky].
> >
> >The patch is supposed to be applied after "xen/blkfront: improve protection
> >against issuing unsupported REQ_FUA".
> >---
> >  drivers/block/xen-blkfront.c | 51 +++++++++++++++++++++++++++-----------------
> >  1 file changed, 31 insertions(+), 20 deletions(-)
> >
> >diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> >index 2e6c103..2236c6f 100644
> >--- a/drivers/block/xen-blkfront.c
> >+++ b/drivers/block/xen-blkfront.c
> >@@ -126,7 +126,6 @@ struct blkfront_info
> >  	unsigned int persistent_gnts_c;
> >  	unsigned long shadow_free;
> >  	unsigned int feature_flush;
> >-	unsigned int flush_op;
> >  	unsigned int feature_discard:1;
> >  	unsigned int feature_secdiscard:1;
> >  	unsigned int discard_granularity;
> >@@ -479,7 +478,19 @@ static int blkif_queue_request(struct request *req)
> >  				 * way.  (It's also a FLUSH+FUA, since it is
> >  				 * guaranteed ordered WRT previous writes.)
> >  				 */
> >-				ring_req->operation = info->flush_op;
> >+				switch (info->feature_flush &
> >+					((REQ_FLUSH|REQ_FUA))) {
> >+				case REQ_FLUSH|REQ_FUA:
> >+					ring_req->operation =
> >+						BLKIF_OP_WRITE_BARRIER;
> >+					break;
> >+				case REQ_FLUSH:
> >+					ring_req->operation =
> >+						BLKIF_OP_FLUSH_DISKCACHE;
> >+					break;
> >+				default:
> >+					ring_req->operation = 0;
> >+				}
> >  			}
> >  			ring_req->u.rw.nr_segments = nseg;
> >  		}
> >@@ -685,20 +696,26 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
> >  	return 0;
> >  }
> >+static const char *flush_info(unsigned int feature_flush)
> >+{
> >+	switch (feature_flush & ((REQ_FLUSH | REQ_FUA))) {
> >+	case REQ_FLUSH|REQ_FUA:
> >+		return "barrier: enabled;";
> >+	case REQ_FLUSH:
> >+		return "flush diskcache: enabled;";
> >+	default:
> >+		return "barrier or flush: disabled;";
> >+	}
> >+}
> >  static void xlvbd_flush(struct blkfront_info *info)
> >  {
> >  	blk_queue_flush(info->rq, info->feature_flush);
> >-	printk(KERN_INFO "blkfront: %s: %s: %s %s %s %s %s\n",
> >-	       info->gd->disk_name,
> >-	       info->flush_op == BLKIF_OP_WRITE_BARRIER ?
> >-		"barrier" : (info->flush_op == BLKIF_OP_FLUSH_DISKCACHE ?
> >-		"flush diskcache" : "barrier or flush"),
> >-	       info->feature_flush ? "enabled;" : "disabled;",
> >-	       "persistent grants:",
> >-	       info->feature_persistent ? "enabled;" : "disabled;",
> >-	       "indirect descriptors:",
> >-	       info->max_indirect_segments ? "enabled;" : "disabled;");
> >+	pr_info("blkfront: %s: %s %s %s %s %s\n",
> >+		info->gd->disk_name, flush_info(info->feature_flush),
> >+		"persistent grants:", info->feature_persistent ?
> >+		"enabled;" : "disabled;", "indirect descriptors:",
> >+		info->max_indirect_segments ? "enabled;" : "disabled;");
> >  }
> >  static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
> >@@ -1190,7 +1207,6 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
> >  				if (error == -EOPNOTSUPP)
> >  					error = 0;
> >  				info->feature_flush = 0;
> >-				info->flush_op = 0;
> >  				xlvbd_flush(info);
> >  			}
> >  			/* fall through */
> >@@ -1810,7 +1826,6 @@ static void blkfront_connect(struct blkfront_info *info)
> >  		physical_sector_size = sector_size;
> >  	info->feature_flush = 0;
> >-	info->flush_op = 0;
> >  	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
> >  			    "feature-barrier", "%d", &barrier,
> >@@ -1823,10 +1838,8 @@ static void blkfront_connect(struct blkfront_info *info)
> >  	 *
> >  	 * If there are barriers, then we use flush.
> >  	 */
> >-	if (!err && barrier) {
> >+	if (!err && barrier)
> >  		info->feature_flush = REQ_FLUSH | REQ_FUA;
> >-		info->flush_op = BLKIF_OP_WRITE_BARRIER;
> >-	}
> >  	/*
> >  	 * And if there is "feature-flush-cache" use that above
> >  	 * barriers.
> >@@ -1835,10 +1848,8 @@ static void blkfront_connect(struct blkfront_info *info)
> >  			    "feature-flush-cache", "%d", &flush,
> >  			    NULL);
> >-	if (!err && flush) {
> >+	if (!err && flush)
> >  		info->feature_flush = REQ_FLUSH;
> >-		info->flush_op = BLKIF_OP_FLUSH_DISKCACHE;
> >-	}
> >  	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
> >  			    "feature-discard", "%d", &discard,
>