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

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

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,
>