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[Xen-devel] [PATCH v2 6/7] xen-blkback: expand map/unmap functions



Preparatory change for implementing indirect descriptors. Change
xen_blkbk_{map/unmap} in order to be able to map/unmap a random amount
of grants (previously it was limited to
BLKIF_MAX_SEGMENTS_PER_REQUEST). Also, remove the usage of pending_req
in the map/unmap functions, so we can map/unmap grants without needing
to pass a pending_req.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxx
---
 drivers/block/xen-blkback/blkback.c |  141 +++++++++++++++++++++--------------
 1 files changed, 86 insertions(+), 55 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index 90a5755..356722f 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -163,10 +163,6 @@ static inline void shrink_free_pagepool(struct xen_blkif 
*blkif, int num)
 
 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 
-#define pending_handle(_req, _seg) \
-       (_req->grant_handles[_seg])
-
-
 static int do_block_io_op(struct xen_blkif *blkif);
 static int dispatch_rw_block_io(struct xen_blkif *blkif,
                                struct blkif_request *req,
@@ -648,50 +644,57 @@ struct seg_buf {
  * Unmap the grant references, and also remove the M2P over-rides
  * used in the 'pending_req'.
  */
-static void xen_blkbk_unmap(struct pending_req *req)
+static void xen_blkbk_unmap(struct xen_blkif *blkif,
+                            grant_handle_t handles[],
+                            struct page *pages[],
+                            struct persistent_gnt *persistent_gnts[],
+                            int num)
 {
        struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-       struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+       struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        unsigned int i, invcount = 0;
-       grant_handle_t handle;
-       struct xen_blkif *blkif = req->blkif;
        int ret;
 
-       for (i = 0; i < req->nr_pages; i++) {
-               if (req->persistent_gnts[i] != NULL) {
-                       put_persistent_gnt(blkif, req->persistent_gnts[i]);
+       for (i = 0; i < num; i++) {
+               if (persistent_gnts[i] != NULL) {
+                       put_persistent_gnt(blkif, persistent_gnts[i]);
                        continue;
                }
-               handle = pending_handle(req, i);
-               pages[invcount] = req->pages[i];
-               if (handle == BLKBACK_INVALID_HANDLE)
+               if (handles[i] == BLKBACK_INVALID_HANDLE)
                        continue;
-               gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[invcount]),
-                                   GNTMAP_host_map, handle);
-               pending_handle(req, i) = BLKBACK_INVALID_HANDLE;
-               invcount++;
+               unmap_pages[invcount] = pages[i];
+               gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[i]),
+                                   GNTMAP_host_map, handles[i]);
+               handles[i] = BLKBACK_INVALID_HANDLE;
+               if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
+                       ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
+                                               invcount);
+                       BUG_ON(ret);
+                       put_free_pages(blkif, unmap_pages, invcount);
+                       invcount = 0;
+               }
+       }
+       if (invcount) {
+               ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
+               BUG_ON(ret);
+               put_free_pages(blkif, unmap_pages, invcount);
        }
-
-       ret = gnttab_unmap_refs(unmap, NULL, pages, invcount);
-       BUG_ON(ret);
-       put_free_pages(blkif, pages, invcount);
 }
 
-static int xen_blkbk_map(struct blkif_request *req,
-                        struct pending_req *pending_req,
-                        struct seg_buf seg[],
-                        struct page *pages[])
+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[],
+                        int num, bool ro)
 {
        struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-       struct persistent_gnt **persistent_gnts = pending_req->persistent_gnts;
        struct persistent_gnt *persistent_gnt = NULL;
-       struct xen_blkif *blkif = pending_req->blkif;
        phys_addr_t addr = 0;
        int i, seg_idx, new_map_idx;
-       int nseg = req->u.rw.nr_segments;
        int segs_to_map = 0;
        int ret = 0;
+       int last_map = 0, map_until = 0;
        int use_persistent_gnts;
 
        use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
@@ -701,13 +704,14 @@ static int xen_blkbk_map(struct blkif_request *req,
         * assign map[..] with the PFN of the page in our domain with the
         * corresponding grant reference for each page.
         */
-       for (i = 0; i < nseg; i++) {
+again:
+       for (i = map_until; i < num; i++) {
                uint32_t flags;
 
                if (use_persistent_gnts)
                        persistent_gnt = get_persistent_gnt(
                                blkif,
-                               req->u.rw.seg[i].gref);
+                               grefs[i]);
 
                if (persistent_gnt) {
                        /*
@@ -723,13 +727,15 @@ static int xen_blkbk_map(struct blkif_request *req,
                        pages_to_gnt[segs_to_map] = pages[i];
                        persistent_gnts[i] = NULL;
                        flags = GNTMAP_host_map;
-                       if (!use_persistent_gnts &&
-                           (pending_req->operation != BLKIF_OP_READ))
+                       if (!use_persistent_gnts && ro)
                                flags |= GNTMAP_readonly;
                        gnttab_set_map_op(&map[segs_to_map++], addr,
-                                         flags, req->u.rw.seg[i].gref,
+                                         flags, grefs[i],
                                          blkif->domid);
                }
+               map_until = i + 1;
+               if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
+                       break;
        }
 
        if (segs_to_map) {
@@ -742,26 +748,19 @@ static int xen_blkbk_map(struct blkif_request *req,
         * so that when we access vaddr(pending_req,i) it has the contents of
         * the page from the other domain.
         */
-       for (seg_idx = 0, new_map_idx = 0; seg_idx < nseg; seg_idx++) {
+       for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; 
seg_idx++) {
                if (!persistent_gnts[seg_idx]) {
                        /* 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");
-                               pending_handle(pending_req, seg_idx) = 
BLKBACK_INVALID_HANDLE;
+                               handles[seg_idx] = BLKBACK_INVALID_HANDLE;
                                ret |= 1;
-                               new_map_idx++;
-                               /*
-                                * No need to set unmap_seg bit, since
-                                * we can not unmap this grant because
-                                * the handle is invalid.
-                                */
-                               continue;
+                               goto next;
                        }
-                       pending_handle(pending_req, seg_idx) = 
map[new_map_idx].handle;
+                       handles[seg_idx] = map[new_map_idx].handle;
                } else {
-                       /* This grant is persistent and already mapped */
-                       goto next;
+                       continue;
                }
                if (use_persistent_gnts &&
                    blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
@@ -777,7 +776,7 @@ static int xen_blkbk_map(struct blkif_request *req,
                                 * allocate the persistent_gnt struct
                                 * map this grant non-persistenly
                                 */
-                               goto next_unmap;
+                               goto next;
                        }
                        persistent_gnt->gnt = map[new_map_idx].ref;
                        persistent_gnt->handle = map[new_map_idx].handle;
@@ -786,13 +785,12 @@ static int xen_blkbk_map(struct blkif_request *req,
                                               persistent_gnt)) {
                                kfree(persistent_gnt);
                                persistent_gnt = NULL;
-                               goto next_unmap;
+                               goto next;
                        }
                        persistent_gnts[seg_idx] = 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);
-                       new_map_idx++;
                        goto next;
                }
                if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
@@ -800,15 +798,18 @@ static int xen_blkbk_map(struct blkif_request *req,
                        pr_debug(DRV_PFX " domain %u, device %#x is using 
maximum number of persistent grants\n",
                                 blkif->domid, blkif->vbd.handle);
                }
-next_unmap:
                /*
                 * We could not map this grant persistently, so use it as
                 * a non-persistent grant.
                 */
-               new_map_idx++;
 next:
-               seg[seg_idx].offset = (req->u.rw.seg[seg_idx].first_sect << 9);
+               new_map_idx++;
        }
+       segs_to_map = 0;
+       last_map = map_until;
+       if (map_until != num)
+               goto again;
+
        return ret;
 
 out_of_memory:
@@ -817,6 +818,31 @@ out_of_memory:
        return -ENOMEM;
 }
 
+static int xen_blkbk_map_seg(struct blkif_request *req,
+                            struct pending_req *pending_req,
+                            struct seg_buf seg[],
+                            struct page *pages[])
+{
+       int i, rc;
+       grant_ref_t grefs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+
+       for (i = 0; i < req->u.rw.nr_segments; i++)
+               grefs[i] = req->u.rw.seg[i].gref;
+
+       rc = xen_blkbk_map(pending_req->blkif, grefs,
+                          pending_req->persistent_gnts,
+                          pending_req->grant_handles, pending_req->pages,
+                          req->u.rw.nr_segments,
+                          (pending_req->operation != BLKIF_OP_READ));
+       if (rc)
+               return rc;
+
+       for (i = 0; i < req->u.rw.nr_segments; i++)
+               seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
+
+       return 0;
+}
+
 static int dispatch_discard_io(struct xen_blkif *blkif,
                                struct blkif_request *req)
 {
@@ -903,7 +929,10 @@ 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);
+               xen_blkbk_unmap(pending_req->blkif, pending_req->grant_handles,
+                               pending_req->pages,
+                               pending_req->persistent_gnts,
+                               pending_req->nr_pages);
                make_response(pending_req->blkif, pending_req->id,
                              pending_req->operation, pending_req->status);
                xen_blkif_put(pending_req->blkif);
@@ -1125,7 +1154,7 @@ 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(req, pending_req, seg, pages))
+       if (xen_blkbk_map_seg(req, pending_req, seg, pages))
                goto fail_flush;
 
        /*
@@ -1186,7 +1215,9 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
        return 0;
 
  fail_flush:
-       xen_blkbk_unmap(pending_req);
+       xen_blkbk_unmap(blkif, pending_req->grant_handles,
+                       pending_req->pages, pending_req->persistent_gnts,
+                       pending_req->nr_pages);
  fail_response:
        /* Haven't submitted any bio's yet. */
        make_response(blkif, req->u.rw.id, req->operation, BLKIF_RSP_ERROR);
-- 
1.7.7.5 (Apple Git-26)


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