xen-blkback: allocate list of pending reqs in small chunks

Allocate pending requests in smaller chunks instead of allocating them
all at the same time.

This change also removes the global array of pending_reqs, it is no
longer necessay.

Variables related to the grant mapping have been grouped into a struct
called "grant_page", this allows to allocate them in smaller chunks,
and also improves memory locality.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Tested-by: Sander Eikelenboom <linux@eikelenboom.it>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/block/xen-blkback/blkback.c

@@ -641,9 +641,7 @@ purge_gnt_list:
  * used in the 'pending_req'.
  */
 static void xen_blkbk_unmap(struct xen_blkif *blkif,
-                            grant_handle_t handles[],
-                            struct page *pages[],
-                            struct persistent_gnt *persistent_gnts[],
+                            struct grant_page *pages[],
                             int num)
 {
 	struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
@@ -652,16 +650,16 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
 	int ret;
 
 	for (i = 0; i < num; i++) {
-		if (persistent_gnts[i] != NULL) {
-			put_persistent_gnt(blkif, persistent_gnts[i]);
+		if (pages[i]->persistent_gnt != NULL) {
+			put_persistent_gnt(blkif, pages[i]->persistent_gnt);
 			continue;
 		}
-		if (handles[i] == BLKBACK_INVALID_HANDLE)
+		if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
 			continue;
-		unmap_pages[invcount] = pages[i];
-		gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[i]),
-				    GNTMAP_host_map, handles[i]);
-		handles[i] = BLKBACK_INVALID_HANDLE;
+		unmap_pages[invcount] = pages[i]->page;
+		gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[i]->page),
+				    GNTMAP_host_map, pages[i]->handle);
+		pages[i]->handle = BLKBACK_INVALID_HANDLE;
 		if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 			ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
 			                        invcount);
@@ -677,10 +675,8 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
 	}
 }
 
-static int xen_blkbk_map(struct xen_blkif *blkif, grant_ref_t grefs[],
-			 struct persistent_gnt *persistent_gnts[],
-			 grant_handle_t handles[],
-			 struct page *pages[],
+static int xen_blkbk_map(struct xen_blkif *blkif,
+			 struct grant_page *pages[],
 			 int num, bool ro)
 {
 	struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
@@ -707,26 +703,26 @@ again:
 		if (use_persistent_gnts)
 			persistent_gnt = get_persistent_gnt(
 				blkif,
-				grefs[i]);
+				pages[i]->gref);
 
 		if (persistent_gnt) {
 			/*
 			 * We are using persistent grants and
 			 * the grant is already mapped
 			 */
-			pages[i] = persistent_gnt->page;
-			persistent_gnts[i] = persistent_gnt;
+			pages[i]->page = persistent_gnt->page;
+			pages[i]->persistent_gnt = persistent_gnt;
 		} else {
-			if (get_free_page(blkif, &pages[i]))
+			if (get_free_page(blkif, &pages[i]->page))
 				goto out_of_memory;
-			addr = vaddr(pages[i]);
-			pages_to_gnt[segs_to_map] = pages[i];
-			persistent_gnts[i] = NULL;
+			addr = vaddr(pages[i]->page);
+			pages_to_gnt[segs_to_map] = pages[i]->page;
+			pages[i]->persistent_gnt = NULL;
 			flags = GNTMAP_host_map;
 			if (!use_persistent_gnts && ro)
 				flags |= GNTMAP_readonly;
 			gnttab_set_map_op(&map[segs_to_map++], addr,
-					  flags, grefs[i],
+					  flags, pages[i]->gref,
 					  blkif->domid);
 		}
 		map_until = i + 1;
@@ -745,16 +741,16 @@ again:
 	 * the page from the other domain.
 	 */
 	for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) {
-		if (!persistent_gnts[seg_idx]) {
+		if (!pages[seg_idx]->persistent_gnt) {
 			/* This is a newly mapped grant */
 			BUG_ON(new_map_idx >= segs_to_map);
 			if (unlikely(map[new_map_idx].status != 0)) {
 				pr_debug(DRV_PFX "invalid buffer -- could not remap it\n");
-				handles[seg_idx] = BLKBACK_INVALID_HANDLE;
+				pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
 				ret |= 1;
 				goto next;
 			}
-			handles[seg_idx] = map[new_map_idx].handle;
+			pages[seg_idx]->handle = map[new_map_idx].handle;
 		} else {
 			continue;
 		}
@@ -776,14 +772,14 @@ again:
 			}
 			persistent_gnt->gnt = map[new_map_idx].ref;
 			persistent_gnt->handle = map[new_map_idx].handle;
-			persistent_gnt->page = pages[seg_idx];
+			persistent_gnt->page = pages[seg_idx]->page;
 			if (add_persistent_gnt(blkif,
 			                       persistent_gnt)) {
 				kfree(persistent_gnt);
 				persistent_gnt = NULL;
 				goto next;
 			}
-			persistent_gnts[seg_idx] = persistent_gnt;
+			pages[seg_idx]->persistent_gnt = persistent_gnt;
 			pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n",
 				 persistent_gnt->gnt, blkif->persistent_gnt_c,
 				 xen_blkif_max_pgrants);
@@ -814,15 +810,11 @@ out_of_memory:
 	return -ENOMEM;
 }
 
-static int xen_blkbk_map_seg(struct pending_req *pending_req,
-			     struct seg_buf seg[],
-			     struct page *pages[])
+static int xen_blkbk_map_seg(struct pending_req *pending_req)
 {
 	int rc;
 
-	rc = xen_blkbk_map(pending_req->blkif, pending_req->grefs,
-	                   pending_req->persistent_gnts,
-	                   pending_req->grant_handles, pending_req->pages,
+	rc = xen_blkbk_map(pending_req->blkif, pending_req->segments,
 			   pending_req->nr_pages,
 	                   (pending_req->operation != BLKIF_OP_READ));
 
@@ -834,9 +826,7 @@ static int xen_blkbk_parse_indirect(struct blkif_request *req,
 				    struct seg_buf seg[],
 				    struct phys_req *preq)
 {
-	struct persistent_gnt **persistent =
-		pending_req->indirect_persistent_gnts;
-	struct page **pages = pending_req->indirect_pages;
+	struct grant_page **pages = pending_req->indirect_pages;
 	struct xen_blkif *blkif = pending_req->blkif;
 	int indirect_grefs, rc, n, nseg, i;
 	struct blkif_request_segment_aligned *segments = NULL;
@@ -845,9 +835,10 @@ static int xen_blkbk_parse_indirect(struct blkif_request *req,
 	indirect_grefs = INDIRECT_PAGES(nseg);
 	BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 
-	rc = xen_blkbk_map(blkif, req->u.indirect.indirect_grefs,
-			   persistent, pending_req->indirect_handles,
-			   pages, indirect_grefs, true);
+	for (i = 0; i < indirect_grefs; i++)
+		pages[i]->gref = req->u.indirect.indirect_grefs[i];
+
+	rc = xen_blkbk_map(blkif, pages, indirect_grefs, true);
 	if (rc)
 		goto unmap;
 
@@ -856,10 +847,10 @@ static int xen_blkbk_parse_indirect(struct blkif_request *req,
 			/* Map indirect segments */
 			if (segments)
 				kunmap_atomic(segments);
-			segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]);
+			segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page);
 		}
 		i = n % SEGS_PER_INDIRECT_FRAME;
-		pending_req->grefs[n] = segments[i].gref;
+		pending_req->segments[n]->gref = segments[i].gref;
 		seg[n].nsec = segments[i].last_sect -
 			segments[i].first_sect + 1;
 		seg[n].offset = (segments[i].first_sect << 9);
@@ -874,8 +865,7 @@ static int xen_blkbk_parse_indirect(struct blkif_request *req,
 unmap:
 	if (segments)
 		kunmap_atomic(segments);
-	xen_blkbk_unmap(blkif, pending_req->indirect_handles,
-			pages, persistent, indirect_grefs);
+	xen_blkbk_unmap(blkif, pages, indirect_grefs);
 	return rc;
 }
 
@@ -965,9 +955,8 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
 	 * the proper response on the ring.
 	 */
 	if (atomic_dec_and_test(&pending_req->pendcnt)) {
-		xen_blkbk_unmap(pending_req->blkif, pending_req->grant_handles,
-		                pending_req->pages,
-		                pending_req->persistent_gnts,
+		xen_blkbk_unmap(pending_req->blkif,
+		                pending_req->segments,
 		                pending_req->nr_pages);
 		make_response(pending_req->blkif, pending_req->id,
 			      pending_req->operation, pending_req->status);
@@ -1104,7 +1093,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	int operation;
 	struct blk_plug plug;
 	bool drain = false;
-	struct page **pages = pending_req->pages;
+	struct grant_page **pages = pending_req->segments;
 	unsigned short req_operation;
 
 	req_operation = req->operation == BLKIF_OP_INDIRECT ?
@@ -1165,7 +1154,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 		preq.dev               = req->u.rw.handle;
 		preq.sector_number     = req->u.rw.sector_number;
 		for (i = 0; i < nseg; i++) {
-			pending_req->grefs[i] = req->u.rw.seg[i].gref;
+			pages[i]->gref = req->u.rw.seg[i].gref;
 			seg[i].nsec = req->u.rw.seg[i].last_sect -
 				req->u.rw.seg[i].first_sect + 1;
 			seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
@@ -1216,7 +1205,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	 * the hypercall to unmap the grants - that is all done in
 	 * xen_blkbk_unmap.
 	 */
-	if (xen_blkbk_map_seg(pending_req, seg, pages))
+	if (xen_blkbk_map_seg(pending_req))
 		goto fail_flush;
 
 	/*
@@ -1228,7 +1217,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	for (i = 0; i < nseg; i++) {
 		while ((bio == NULL) ||
 		       (bio_add_page(bio,
-				     pages[i],
+				     pages[i]->page,
 				     seg[i].nsec << 9,
 				     seg[i].offset) == 0)) {
 
@@ -1277,8 +1266,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	return 0;
 
  fail_flush:
-	xen_blkbk_unmap(blkif, pending_req->grant_handles,
-	                pending_req->pages, pending_req->persistent_gnts,
+	xen_blkbk_unmap(blkif, pending_req->segments,
 	                pending_req->nr_pages);
  fail_response:
 	/* Haven't submitted any bio's yet. */

drivers/block/xen-blkback/common.h

@@ -297,8 +297,6 @@ struct xen_blkif {
 	int			free_pages_num;
 	struct list_head	free_pages;
 
-	/* Allocation of pending_reqs */
-	struct pending_req	*pending_reqs;
 	/* List of all 'pending_req' available */
 	struct list_head	pending_free;
 	/* And its spinlock. */
@@ -323,6 +321,13 @@ struct seg_buf {
 	unsigned int nsec;
 };
 
+struct grant_page {
+	struct page 		*page;
+	struct persistent_gnt	*persistent_gnt;
+	grant_handle_t		handle;
+	grant_ref_t		gref;
+};
+
 /*
  * Each outstanding request that we've passed to the lower device layers has a
  * 'pending_req' allocated to it. Each buffer_head that completes decrements
@@ -337,14 +342,9 @@ struct pending_req {
 	unsigned short		operation;
 	int			status;
 	struct list_head	free_list;
-	struct page		*pages[MAX_INDIRECT_SEGMENTS];
-	struct persistent_gnt	*persistent_gnts[MAX_INDIRECT_SEGMENTS];
-	grant_handle_t		grant_handles[MAX_INDIRECT_SEGMENTS];
-	grant_ref_t		grefs[MAX_INDIRECT_SEGMENTS];
+	struct grant_page	*segments[MAX_INDIRECT_SEGMENTS];
 	/* Indirect descriptors */
-	struct persistent_gnt	*indirect_persistent_gnts[MAX_INDIRECT_PAGES];
-	struct page		*indirect_pages[MAX_INDIRECT_PAGES];
-	grant_handle_t		indirect_handles[MAX_INDIRECT_PAGES];
+	struct grant_page	*indirect_pages[MAX_INDIRECT_PAGES];
 	struct seg_buf		seg[MAX_INDIRECT_SEGMENTS];
 	struct bio		*biolist[MAX_INDIRECT_SEGMENTS];
 };

drivers/block/xen-blkback/xenbus.c

@@ -105,7 +105,8 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 {
 	struct xen_blkif *blkif;
-	int i;
+	struct pending_req *req, *n;
+	int i, j;
 
 	BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 
@@ -127,22 +128,51 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 	blkif->free_pages_num = 0;
 	atomic_set(&blkif->persistent_gnt_in_use, 0);
 
-	blkif->pending_reqs = kcalloc(XEN_BLKIF_REQS,
-	                              sizeof(blkif->pending_reqs[0]),
-	                              GFP_KERNEL);
-	if (!blkif->pending_reqs) {
-		kmem_cache_free(xen_blkif_cachep, blkif);
-		return ERR_PTR(-ENOMEM);
-	}
 	INIT_LIST_HEAD(&blkif->pending_free);
+
+	for (i = 0; i < XEN_BLKIF_REQS; i++) {
+		req = kzalloc(sizeof(*req), GFP_KERNEL);
+		if (!req)
+			goto fail;
+		list_add_tail(&req->free_list,
+		              &blkif->pending_free);
+		for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
+			req->segments[j] = kzalloc(sizeof(*req->segments[0]),
+			                           GFP_KERNEL);
+			if (!req->segments[j])
+				goto fail;
+		}
+		for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
+			req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
+			                                 GFP_KERNEL);
+			if (!req->indirect_pages[j])
+				goto fail;
+		}
+	}
 	spin_lock_init(&blkif->pending_free_lock);
 	init_waitqueue_head(&blkif->pending_free_wq);
 
-	for (i = 0; i < XEN_BLKIF_REQS; i++)
-		list_add_tail(&blkif->pending_reqs[i].free_list,
-			      &blkif->pending_free);
-
 	return blkif;
+
+fail:
+	list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
+		list_del(&req->free_list);
+		for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
+			if (!req->segments[j])
+				break;
+			kfree(req->segments[j]);
+		}
+		for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
+			if (!req->indirect_pages[j])
+				break;
+			kfree(req->indirect_pages[j]);
+		}
+		kfree(req);
+	}
+
+	kmem_cache_free(xen_blkif_cachep, blkif);
+
+	return ERR_PTR(-ENOMEM);
 }
 
 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
@@ -221,18 +251,28 @@ static void xen_blkif_disconnect(struct xen_blkif *blkif)
 
 static void xen_blkif_free(struct xen_blkif *blkif)
 {
-	struct pending_req *req;
-	int i = 0;
+	struct pending_req *req, *n;
+	int i = 0, j;
 
 	if (!atomic_dec_and_test(&blkif->refcnt))
 		BUG();
 
 	/* Check that there is no request in use */
-	list_for_each_entry(req, &blkif->pending_free, free_list)
+	list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
+		list_del(&req->free_list);
+
+		for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
+			kfree(req->segments[j]);
+
+		for (j = 0; j < MAX_INDIRECT_PAGES; j++)
+			kfree(req->indirect_pages[j]);
+
+		kfree(req);
 		i++;
-	BUG_ON(i != XEN_BLKIF_REQS);
+	}
+
+	WARN_ON(i != XEN_BLKIF_REQS);
 
-	kfree(blkif->pending_reqs);
 	kmem_cache_free(xen_blkif_cachep, blkif);
 }