From: Jake Wires <jake.wires@citrix.com>
Date: Thu, 1 Jul 2010 19:29:06 +0000 (-0700)
Subject: don't retry when there's no point
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=9a3bcd260fd7eb92bcca4b1772c0ddae50b6ab29;p=people%2Fdstodden%2Fblktap.git

don't retry when there's no point

Signed-off-by: Jake Wires <jake.wires@citrix.com>
---

diff --git a/drivers/tapdisk-image.c b/drivers/tapdisk-image.c
index 96ebd4b..f26b6d4 100644
--- a/drivers/tapdisk-image.c
+++ b/drivers/tapdisk-image.c
@@ -77,10 +77,12 @@ tapdisk_image_free(td_image_t *image)
 int
 tapdisk_image_check_td_request(td_image_t *image, td_request_t treq)
 {
-	int rdonly;
+	int rdonly, err;
 	td_driver_t *driver;
 	td_disk_info_t *info;
 
+	err = -EINVAL;
+
 	driver = image->driver;
 	if (!driver)
 		return -ENODEV;
@@ -91,8 +93,10 @@ tapdisk_image_check_td_request(td_image_t *image, td_request_t treq)
 	if (treq.op != TD_OP_READ && treq.op != TD_OP_WRITE)
 		goto fail;
 
-	if (treq.op == TD_OP_WRITE && rdonly)
+	if (treq.op == TD_OP_WRITE && rdonly) {
+		err = -EPERM;
 		goto fail;
+	}
 
 	if (treq.secs <= 0 || treq.sec + treq.secs > info->size)
 		goto fail;
@@ -100,10 +104,10 @@ tapdisk_image_check_td_request(td_image_t *image, td_request_t treq)
 	return 0;
 
 fail:
-	ERR(-EINVAL, "bad td request on %s (%s, %llu): %d at %llu",
+	ERR(err, "bad td request on %s (%s, %llu): %d at %llu",
 	    image->name, (rdonly ? "ro" : "rw"), info->size, treq.op,
 	    treq.sec + treq.secs);
-	return -EINVAL;
+	return err;
 
 }
 
@@ -112,13 +116,14 @@ tapdisk_image_check_ring_request(td_image_t *image, blkif_request_t *req)
 {
 	td_driver_t *driver;
 	td_disk_info_t *info;
-	int i, psize, rdonly;
 	uint64_t nsects, total;
+	int i, err, psize, rdonly;
 
 	driver = image->driver;
 	if (!driver)
 		return -ENODEV;
 
+	err    = -EINVAL;
 	nsects = 0;
 	total  = 0;
 	info   = &driver->info;
@@ -129,8 +134,10 @@ tapdisk_image_check_ring_request(td_image_t *image, blkif_request_t *req)
 	    req->operation != BLKIF_OP_WRITE)
 		goto fail;
 
-	if (req->operation == BLKIF_OP_WRITE && rdonly)
+	if (req->operation == BLKIF_OP_WRITE && rdonly) {
+		err = -EPERM;
 		goto fail;
+	}
 
 	if (!req->nr_segments || req->nr_segments > MAX_SEGMENTS_PER_REQ)
 		goto fail;
@@ -153,8 +160,8 @@ tapdisk_image_check_ring_request(td_image_t *image, blkif_request_t *req)
 	return 0;
 
 fail:
-	ERR(-EINVAL, "bad request on %s (%s, %llu): id: %llu: %d at %llu",
+	ERR(err, "bad request on %s (%s, %llu): id: %llu: %d at %llu",
 	    image->name, (rdonly ? "ro" : "rw"), info->size, req->id,
 	    req->operation, req->sector_number + total);
-	return -EINVAL;
+	return err;
 }
diff --git a/drivers/tapdisk-vbd.c b/drivers/tapdisk-vbd.c
index 4a11a30..b885d6e 100644
--- a/drivers/tapdisk-vbd.c
+++ b/drivers/tapdisk-vbd.c
@@ -1060,7 +1060,8 @@ tapdisk_vbd_queue_ready(td_vbd_t *vbd)
 int
 tapdisk_vbd_retry_needed(td_vbd_t *vbd)
 {
-	return !list_empty(&vbd->failed_requests);
+	return !(list_empty(&vbd->failed_requests) ||
+		 list_empty(&vbd->new_requests));
 }
 
 int
@@ -1425,14 +1426,33 @@ tapdisk_vbd_check_queue(td_vbd_t *vbd)
 	return 0;
 }
 
+static int
+tapdisk_vbd_request_should_retry(td_vbd_t *vbd, td_vbd_request_t *vreq)
+{
+	if (td_flag_test(vbd->state, TD_VBD_DEAD) ||
+	    td_flag_test(vbd->state, TD_VBD_SHUTDOWN_REQUESTED))
+		return 0;
+
+	switch (abs(vreq->error)) {
+	case EPERM:
+	case ENOSYS:
+	case ESTALE:
+	case ENOSPC:
+		return 0;
+	}
+
+	if (tapdisk_vbd_request_timeout(vreq))
+		return 0;
+
+	return 1;
+}
+
 static void
 tapdisk_vbd_complete_vbd_request(td_vbd_t *vbd, td_vbd_request_t *vreq)
 {
 	if (!vreq->submitting && !vreq->secs_pending) {
 		if (vreq->status == BLKIF_RSP_ERROR &&
-		    !tapdisk_vbd_request_timeout(vreq) &&
-		    !td_flag_test(vbd->state, TD_VBD_DEAD) &&
-		    !td_flag_test(vbd->state, TD_VBD_SHUTDOWN_REQUESTED))
+		    tapdisk_vbd_request_should_retry(vbd, vreq))
 			tapdisk_vbd_move_request(vreq, &vbd->failed_requests);
 		else
 			tapdisk_vbd_move_request(vreq, &vbd->completed_requests);
@@ -1605,12 +1625,16 @@ tapdisk_vbd_issue_request(td_vbd_t *vbd, td_vbd_request_t *vreq)
 	tapdisk_vbd_move_request(vreq, &vbd->pending_requests);
 
 	err = tapdisk_vbd_check_queue(vbd);
-	if (err)
+	if (err) {
+		vreq->error = err;
 		goto fail;
+	}
 
 	err = tapdisk_image_check_ring_request(image, req);
-	if (err)
+	if (err) {
+		vreq->error = err;
 		goto fail;
+	}
 
 	memset(&treq, 0, sizeof(td_request_t));
 	for (i = 0; i < req->nr_segments; i++) {
@@ -1672,6 +1696,12 @@ fail:
 	goto out;
 }
 
+static int
+tapdisk_vbd_request_completed(td_vbd_t *vbd, td_vbd_request_t *vreq)
+{
+	return vreq->list_head == &vbd->completed_requests;
+}
+
 static int
 tapdisk_vbd_reissue_failed_requests(td_vbd_t *vbd)
 {
@@ -1705,11 +1735,15 @@ tapdisk_vbd_reissue_failed_requests(td_vbd_t *vbd)
 		    vreq->req.nr_segments);
 
 		err = tapdisk_vbd_issue_request(vbd, vreq);
-		if (err)
+		/*
+		 * if this request failed, but was not completed,
+		 * we'll back off for a while.
+		 */
+		if (err && !tapdisk_vbd_request_completed(vbd, vreq))
 			break;
 	}
 
-	return err;
+	return 0;
 }
 
 static int
@@ -1720,7 +1754,11 @@ tapdisk_vbd_issue_new_requests(td_vbd_t *vbd)
 
 	tapdisk_vbd_for_each_request(vreq, tmp, &vbd->new_requests) {
 		err = tapdisk_vbd_issue_request(vbd, vreq);
-		if (err)
+		/*
+		 * if this request failed, but was not completed,
+		 * we'll back off for a while.
+		 */
+		if (err && !tapdisk_vbd_request_completed(vbd, vreq))
 			return err;
 	}
 
diff --git a/drivers/tapdisk-vbd.h b/drivers/tapdisk-vbd.h
index 70a0a78..90711ad 100644
--- a/drivers/tapdisk-vbd.h
+++ b/drivers/tapdisk-vbd.h
@@ -77,6 +77,7 @@ struct td_vbd_request {
 
 	td_vbd_t                   *vbd;
 	struct list_head            next;
+	struct list_head           *list_head;
 };
 
 struct td_vbd_handle {
@@ -137,6 +138,7 @@ tapdisk_vbd_move_request(td_vbd_request_t *vreq, struct list_head *dest)
 	list_del(&vreq->next);
 	INIT_LIST_HEAD(&vreq->next);
 	list_add_tail(&vreq->next, dest);
+	vreq->list_head = dest;
 }
 
 static inline void