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>

1 files changed, 40 insertions, 52 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 1ebc0aa0f0e4..e79ab4559233 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/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. */