1 files changed, 131 insertions, 28 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 8d53ed293606..432db1b59b00 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -121,7 +121,8 @@ struct blkfront_info
 	struct work_struct work;
 	struct gnttab_free_callback callback;
 	struct blk_shadow shadow[BLK_RING_SIZE];
-	struct list_head persistent_gnts;
+	struct list_head grants;
+	struct list_head indirect_pages;
 	unsigned int persistent_gnts_c;
 	unsigned long shadow_free;
 	unsigned int feature_flush;
@@ -200,15 +201,17 @@ static int fill_grant_buffer(struct blkfront_info *info, int num)
 		if (!gnt_list_entry)
 			goto out_of_memory;
 
-		granted_page = alloc_page(GFP_NOIO);
-		if (!granted_page) {
-			kfree(gnt_list_entry);
-			goto out_of_memory;
+		if (info->feature_persistent) {
+			granted_page = alloc_page(GFP_NOIO);
+			if (!granted_page) {
+				kfree(gnt_list_entry);
+				goto out_of_memory;
+			}
+			gnt_list_entry->pfn = page_to_pfn(granted_page);
 		}
 
-		gnt_list_entry->pfn = page_to_pfn(granted_page);
 		gnt_list_entry->gref = GRANT_INVALID_REF;
-		list_add(&gnt_list_entry->node, &info->persistent_gnts);
+		list_add(&gnt_list_entry->node, &info->grants);
 		i++;
 	}
 
@@ -216,9 +219,10 @@ static int fill_grant_buffer(struct blkfront_info *info, int num)
 
 out_of_memory:
 	list_for_each_entry_safe(gnt_list_entry, n,
-	                         &info->persistent_gnts, node) {
+	                         &info->grants, node) {
 		list_del(&gnt_list_entry->node);
-		__free_page(pfn_to_page(gnt_list_entry->pfn));
+		if (info->feature_persistent)
+			__free_page(pfn_to_page(gnt_list_entry->pfn));
 		kfree(gnt_list_entry);
 		i--;
 	}
@@ -227,13 +231,14 @@ out_of_memory:
 }
 
 static struct grant *get_grant(grant_ref_t *gref_head,
+                               unsigned long pfn,
                                struct blkfront_info *info)
 {
 	struct grant *gnt_list_entry;
 	unsigned long buffer_mfn;
 
-	BUG_ON(list_empty(&info->persistent_gnts));
-	gnt_list_entry = list_first_entry(&info->persistent_gnts, struct grant,
+	BUG_ON(list_empty(&info->grants));
+	gnt_list_entry = list_first_entry(&info->grants, struct grant,
 	                                  node);
 	list_del(&gnt_list_entry->node);
 
@@ -245,6 +250,10 @@ static struct grant *get_grant(grant_ref_t *gref_head,
 	/* Assign a gref to this page */
 	gnt_list_entry->gref = gnttab_claim_grant_reference(gref_head);
 	BUG_ON(gnt_list_entry->gref == -ENOSPC);
+	if (!info->feature_persistent) {
+		BUG_ON(!pfn);
+		gnt_list_entry->pfn = pfn;
+	}
 	buffer_mfn = pfn_to_mfn(gnt_list_entry->pfn);
 	gnttab_grant_foreign_access_ref(gnt_list_entry->gref,
 	                                info->xbdev->otherend_id,
@@ -400,10 +409,13 @@ static int blkif_queue_request(struct request *req)
 	if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
 		return 1;
 
-	max_grefs = info->max_indirect_segments ?
-		    info->max_indirect_segments +
-		    INDIRECT_GREFS(info->max_indirect_segments) :
-		    BLKIF_MAX_SEGMENTS_PER_REQUEST;
+	max_grefs = req->nr_phys_segments;
+	if (max_grefs > BLKIF_MAX_SEGMENTS_PER_REQUEST)
+		/*
+		 * If we are using indirect segments we need to account
+		 * for the indirect grefs used in the request.
+		 */
+		max_grefs += INDIRECT_GREFS(req->nr_phys_segments);
 
 	/* Check if we have enough grants to allocate a requests */
 	if (info->persistent_gnts_c < max_grefs) {
@@ -477,22 +489,34 @@ static int blkif_queue_request(struct request *req)
 
 			if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
 			    (i % SEGS_PER_INDIRECT_FRAME == 0)) {
+				unsigned long pfn;
+
 				if (segments)
 					kunmap_atomic(segments);
 
 				n = i / SEGS_PER_INDIRECT_FRAME;
-				gnt_list_entry = get_grant(&gref_head, info);
+				if (!info->feature_persistent) {
+					struct page *indirect_page;
+
+					/* Fetch a pre-allocated page to use for indirect grefs */
+					BUG_ON(list_empty(&info->indirect_pages));
+					indirect_page = list_first_entry(&info->indirect_pages,
+					                                 struct page, lru);
+					list_del(&indirect_page->lru);
+					pfn = page_to_pfn(indirect_page);
+				}
+				gnt_list_entry = get_grant(&gref_head, pfn, info);
 				info->shadow[id].indirect_grants[n] = gnt_list_entry;
 				segments = kmap_atomic(pfn_to_page(gnt_list_entry->pfn));
 				ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
 			}
 
-			gnt_list_entry = get_grant(&gref_head, info);
+			gnt_list_entry = get_grant(&gref_head, page_to_pfn(sg_page(sg)), info);
 			ref = gnt_list_entry->gref;
 
 			info->shadow[id].grants_used[i] = gnt_list_entry;
 
-			if (rq_data_dir(req)) {
+			if (rq_data_dir(req) && info->feature_persistent) {
 				char *bvec_data;
 				void *shared_data;
 
@@ -904,21 +928,36 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 		blk_stop_queue(info->rq);
 
 	/* Remove all persistent grants */
-	if (!list_empty(&info->persistent_gnts)) {
+	if (!list_empty(&info->grants)) {
 		list_for_each_entry_safe(persistent_gnt, n,
-		                         &info->persistent_gnts, node) {
+		                         &info->grants, node) {
 			list_del(&persistent_gnt->node);
 			if (persistent_gnt->gref != GRANT_INVALID_REF) {
 				gnttab_end_foreign_access(persistent_gnt->gref,
 				                          0, 0UL);
 				info->persistent_gnts_c--;
 			}
-			__free_page(pfn_to_page(persistent_gnt->pfn));
+			if (info->feature_persistent)
+				__free_page(pfn_to_page(persistent_gnt->pfn));
 			kfree(persistent_gnt);
 		}
 	}
 	BUG_ON(info->persistent_gnts_c != 0);
 
+	/*
+	 * Remove indirect pages, this only happens when using indirect
+	 * descriptors but not persistent grants
+	 */
+	if (!list_empty(&info->indirect_pages)) {
+		struct page *indirect_page, *n;
+
+		BUG_ON(info->feature_persistent);
+		list_for_each_entry_safe(indirect_page, n, &info->indirect_pages, lru) {
+			list_del(&indirect_page->lru);
+			__free_page(indirect_page);
+		}
+	}
+
 	for (i = 0; i < BLK_RING_SIZE; i++) {
 		/*
 		 * Clear persistent grants present in requests already
@@ -933,7 +972,8 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 		for (j = 0; j < segs; j++) {
 			persistent_gnt = info->shadow[i].grants_used[j];
 			gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
-			__free_page(pfn_to_page(persistent_gnt->pfn));
+			if (info->feature_persistent)
+				__free_page(pfn_to_page(persistent_gnt->pfn));
 			kfree(persistent_gnt);
 		}
 
@@ -992,7 +1032,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
 	nseg = s->req.operation == BLKIF_OP_INDIRECT ?
 		s->req.u.indirect.nr_segments : s->req.u.rw.nr_segments;
 
-	if (bret->operation == BLKIF_OP_READ) {
+	if (bret->operation == BLKIF_OP_READ && info->feature_persistent) {
 		/*
 		 * Copy the data received from the backend into the bvec.
 		 * Since bv_offset can be different than 0, and bv_len different
@@ -1013,13 +1053,51 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
 	}
 	/* Add the persistent grant into the list of free grants */
 	for (i = 0; i < nseg; i++) {
-		list_add(&s->grants_used[i]->node, &info->persistent_gnts);
-		info->persistent_gnts_c++;
+		if (gnttab_query_foreign_access(s->grants_used[i]->gref)) {
+			/*
+			 * If the grant is still mapped by the backend (the
+			 * backend has chosen to make this grant persistent)
+			 * we add it at the head of the list, so it will be
+			 * reused first.
+			 */
+			if (!info->feature_persistent)
+				pr_alert_ratelimited("backed has not unmapped grant: %u\n",
+						     s->grants_used[i]->gref);
+			list_add(&s->grants_used[i]->node, &info->grants);
+			info->persistent_gnts_c++;
+		} else {
+			/*
+			 * If the grant is not mapped by the backend we end the
+			 * foreign access and add it to the tail of the list,
+			 * so it will not be picked again unless we run out of
+			 * persistent grants.
+			 */
+			gnttab_end_foreign_access(s->grants_used[i]->gref, 0, 0UL);
+			s->grants_used[i]->gref = GRANT_INVALID_REF;
+			list_add_tail(&s->grants_used[i]->node, &info->grants);
+		}
 	}
 	if (s->req.operation == BLKIF_OP_INDIRECT) {
 		for (i = 0; i < INDIRECT_GREFS(nseg); i++) {
-			list_add(&s->indirect_grants[i]->node, &info->persistent_gnts);
-			info->persistent_gnts_c++;
+			if (gnttab_query_foreign_access(s->indirect_grants[i]->gref)) {
+				if (!info->feature_persistent)
+					pr_alert_ratelimited("backed has not unmapped grant: %u\n",
+							     s->indirect_grants[i]->gref);
+				list_add(&s->indirect_grants[i]->node, &info->grants);
+				info->persistent_gnts_c++;
+			} else {
+				struct page *indirect_page;
+
+				gnttab_end_foreign_access(s->indirect_grants[i]->gref, 0, 0UL);
+				/*
+				 * Add the used indirect page back to the list of
+				 * available pages for indirect grefs.
+				 */
+				indirect_page = pfn_to_page(s->indirect_grants[i]->pfn);
+				list_add(&indirect_page->lru, &info->indirect_pages);
+				s->indirect_grants[i]->gref = GRANT_INVALID_REF;
+				list_add_tail(&s->indirect_grants[i]->node, &info->grants);
+			}
 		}
 	}
 }
@@ -1313,7 +1391,8 @@ static int blkfront_probe(struct xenbus_device *dev,
 	spin_lock_init(&info->io_lock);
 	info->xbdev = dev;
 	info->vdevice = vdevice;
-	INIT_LIST_HEAD(&info->persistent_gnts);
+	INIT_LIST_HEAD(&info->grants);
+	INIT_LIST_HEAD(&info->indirect_pages);
 	info->persistent_gnts_c = 0;
 	info->connected = BLKIF_STATE_DISCONNECTED;
 	INIT_WORK(&info->work, blkif_restart_queue);
@@ -1609,6 +1688,23 @@ static int blkfront_setup_indirect(struct blkfront_info *info)
 	if (err)
 		goto out_of_memory;
 
+	if (!info->feature_persistent && info->max_indirect_segments) {
+		/*
+		 * We are using indirect descriptors but not persistent
+		 * grants, we need to allocate a set of pages that can be
+		 * used for mapping indirect grefs
+		 */
+		int num = INDIRECT_GREFS(segs) * BLK_RING_SIZE;
+
+		BUG_ON(!list_empty(&info->indirect_pages));
+		for (i = 0; i < num; i++) {
+			struct page *indirect_page = alloc_page(GFP_NOIO);
+			if (!indirect_page)
+				goto out_of_memory;
+			list_add(&indirect_page->lru, &info->indirect_pages);
+		}
+	}
+
 	for (i = 0; i < BLK_RING_SIZE; i++) {
 		info->shadow[i].grants_used = kzalloc(
 			sizeof(info->shadow[i].grants_used[0]) * segs,
@@ -1639,6 +1735,13 @@ out_of_memory:
 		kfree(info->shadow[i].indirect_grants);
 		info->shadow[i].indirect_grants = NULL;
 	}
+	if (!list_empty(&info->indirect_pages)) {
+		struct page *indirect_page, *n;
+		list_for_each_entry_safe(indirect_page, n, &info->indirect_pages, lru) {
+			list_del(&indirect_page->lru);
+			__free_page(indirect_page);
+		}
+	}
 	return -ENOMEM;
 }