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authorDongli Zhang <dongli.zhang@oracle.com>2017-06-28 15:57:28 +0300
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2017-07-25 18:31:09 +0300
commitbd912ef3e46b6edb51bb8af4b73fd2be7817e305 (patch)
tree61b5281d5730da8d913a400b63182e64375bdc02 /drivers/block/xen-blkfront.c
parent4b422cb99836de3d261faec20a0329385bdec43d (diff)
downloadlinux-bd912ef3e46b6edb51bb8af4b73fd2be7817e305.tar.xz
xen/blkfront: always allocate grants first from per-queue persistent grants
This patch partially reverts 3df0e50 ("xen/blkfront: pseudo support for multi hardware queues/rings"). The xen-blkfront queue/ring might hang due to grants allocation failure in the situation when gnttab_free_head is almost empty while many persistent grants are reserved for this queue/ring. As persistent grants management was per-queue since 73716df ("xen/blkfront: make persistent grants pool per-queue"), we should always allocate from persistent grants first. Acked-by: Roger Pau Monné <roger.pau@citrix.com> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block/xen-blkfront.c')
-rw-r--r--drivers/block/xen-blkfront.c19
1 files changed, 11 insertions, 8 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 04eeb540490f..98e34e4c62b8 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -708,6 +708,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
* existing persistent grants, or if we have to get new grants,
* as there are not sufficiently many free.
*/
+ bool new_persistent_gnts = false;
struct scatterlist *sg;
int num_sg, max_grefs, num_grant;
@@ -719,19 +720,21 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
*/
max_grefs += INDIRECT_GREFS(max_grefs);
- /*
- * We have to reserve 'max_grefs' grants because persistent
- * grants are shared by all rings.
- */
- if (max_grefs > 0)
- if (gnttab_alloc_grant_references(max_grefs, &setup.gref_head) < 0) {
+ /* Check if we have enough persistent grants to allocate a requests */
+ if (rinfo->persistent_gnts_c < max_grefs) {
+ new_persistent_gnts = true;
+
+ if (gnttab_alloc_grant_references(
+ max_grefs - rinfo->persistent_gnts_c,
+ &setup.gref_head) < 0) {
gnttab_request_free_callback(
&rinfo->callback,
blkif_restart_queue_callback,
rinfo,
- max_grefs);
+ max_grefs - rinfo->persistent_gnts_c);
return 1;
}
+ }
/* Fill out a communications ring structure. */
id = blkif_ring_get_request(rinfo, req, &ring_req);
@@ -832,7 +835,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
if (unlikely(require_extra_req))
rinfo->shadow[extra_id].req = *extra_ring_req;
- if (max_grefs > 0)
+ if (new_persistent_gnts)
gnttab_free_grant_references(setup.gref_head);
return 0;