1 files changed, 52 insertions, 29 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index da18046d0e07..64c60edcdfbc 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -285,7 +285,8 @@ static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
 
                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
                         !rb_next(&persistent_gnt->node)) {
-                        ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
+                        ret = gnttab_unmap_refs(unmap, NULL, pages,
+                                segs_to_unmap);
                         BUG_ON(ret);
                         put_free_pages(blkif, pages, segs_to_unmap);
                         segs_to_unmap = 0;
@@ -298,7 +299,7 @@ static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
         BUG_ON(num != 0);
 }
 
-static void unmap_purged_grants(struct work_struct *work)
+void xen_blkbk_unmap_purged_grants(struct work_struct *work)
 {
         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
@@ -320,7 +321,8 @@ static void unmap_purged_grants(struct work_struct *work)
                 pages[segs_to_unmap] = persistent_gnt->page;
 
                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
-                        ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
+                        ret = gnttab_unmap_refs(unmap, NULL, pages,
+                                segs_to_unmap);
                         BUG_ON(ret);
                         put_free_pages(blkif, pages, segs_to_unmap);
                         segs_to_unmap = 0;
@@ -328,7 +330,7 @@ static void unmap_purged_grants(struct work_struct *work)
                 kfree(persistent_gnt);
         }
         if (segs_to_unmap > 0) {
-                ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
+                ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap);
                 BUG_ON(ret);
                 put_free_pages(blkif, pages, segs_to_unmap);
         }
@@ -373,7 +375,7 @@ static void purge_persistent_gnt(struct xen_blkif *blkif)
 
         pr_debug(DRV_PFX "Going to purge %u persistent grants\n", num_clean);
 
-        INIT_LIST_HEAD(&blkif->persistent_purge_list);
+        BUG_ON(!list_empty(&blkif->persistent_purge_list));
         root = &blkif->persistent_gnts;
 purge_list:
         foreach_grant_safe(persistent_gnt, n, root, node) {
@@ -418,7 +420,6 @@ finished:
         blkif->vbd.overflow_max_grants = 0;
 
         /* We can defer this work */
-        INIT_WORK(&blkif->persistent_purge_work, unmap_purged_grants);
         schedule_work(&blkif->persistent_purge_work);
         pr_debug(DRV_PFX "Purged %u/%u\n", (total - num_clean), total);
         return;
@@ -623,9 +624,23 @@ purge_gnt_list:
                         print_stats(blkif);
         }
 
-        /* Since we are shutting down remove all pages from the buffer */
-        shrink_free_pagepool(blkif, 0 /* All */);
+        /* Drain pending purge work */
+        flush_work(&blkif->persistent_purge_work);
 
+        if (log_stats)
+                print_stats(blkif);
+
+        blkif->xenblkd = NULL;
+        xen_blkif_put(blkif);
+
+        return 0;
+}
+
+/*
+ * Remove persistent grants and empty the pool of free pages
+ */
+void xen_blkbk_free_caches(struct xen_blkif *blkif)
+{
         /* Free all persistent grant pages */
         if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
                 free_persistent_gnts(blkif, &blkif->persistent_gnts,
@@ -634,13 +649,8 @@ purge_gnt_list:
         BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
         blkif->persistent_gnt_c = 0;
 
-        if (log_stats)
-                print_stats(blkif);
-
-        blkif->xenblkd = NULL;
-        xen_blkif_put(blkif);
-
-        return 0;
+        /* Since we are shutting down remove all pages from the buffer */
+        shrink_free_pagepool(blkif, 0 /* All */);
 }
 
 /*
@@ -668,14 +678,15 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
                                     GNTMAP_host_map, pages[i]->handle);
                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
                 if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
-                        ret = gnttab_unmap_refs(unmap, unmap_pages, invcount);
+                        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, unmap_pages, invcount);
+                ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
                 BUG_ON(ret);
                 put_free_pages(blkif, unmap_pages, invcount);
         }
@@ -737,7 +748,7 @@ again:
         }
 
         if (segs_to_map) {
-                ret = gnttab_map_refs(map, pages_to_gnt, segs_to_map);
+                ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
                 BUG_ON(ret);
         }
 
@@ -835,7 +846,7 @@ static int xen_blkbk_parse_indirect(struct blkif_request *req,
         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;
+        struct blkif_request_segment *segments = NULL;
 
         nseg = pending_req->nr_pages;
         indirect_grefs = INDIRECT_PAGES(nseg);
@@ -931,9 +942,7 @@ static void xen_blk_drain_io(struct xen_blkif *blkif)
 {
         atomic_set(&blkif->drain, 1);
         do {
-                /* The initial value is one, and one refcnt taken at the
-                 * start of the xen_blkif_schedule thread. */
-                if (atomic_read(&blkif->refcnt) <= 2)
+                if (atomic_read(&blkif->inflight) == 0)
                         break;
                 wait_for_completion_interruptible_timeout(
                                 &blkif->drain_complete, HZ);
@@ -973,17 +982,30 @@ 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,
+                struct xen_blkif *blkif = pending_req->blkif;
+
+                xen_blkbk_unmap(blkif,
                                 pending_req->segments,
                                 pending_req->nr_pages);
-                make_response(pending_req->blkif, pending_req->id,
+                make_response(blkif, pending_req->id,
                               pending_req->operation, pending_req->status);
-                xen_blkif_put(pending_req->blkif);
-                if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
-                        if (atomic_read(&pending_req->blkif->drain))
-                                complete(&pending_req->blkif->drain_complete);
+                free_req(blkif, pending_req);
+                /*
+                 * Make sure the request is freed before releasing blkif,
+                 * or there could be a race between free_req and the
+                 * cleanup done in xen_blkif_free during shutdown.
+                 *
+                 * NB: The fact that we might try to wake up pending_free_wq
+                 * before drain_complete (in case there's a drain going on)
+                 * it's not a problem with our current implementation
+                 * because we can assure there's no thread waiting on
+                 * pending_free_wq if there's a drain going on, but it has
+                 * to be taken into account if the current model is changed.
+                 */
+                if (atomic_dec_and_test(&blkif->inflight) && atomic_read(&blkif->drain)) {
+                        complete(&blkif->drain_complete);
                 }
-                free_req(pending_req->blkif, pending_req);
+                xen_blkif_put(blkif);
         }
 }
 
@@ -1237,6 +1259,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
          */
         xen_blkif_get(blkif);
+        atomic_inc(&blkif->inflight);
 
         for (i = 0; i < nseg; i++) {
                 while ((bio == NULL) ||