Merge branch 'for-linus' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "This contains a set of fixes for xen-blkback by way of Konrad, and a
  performance regression fix for blk-mq for shared tags.

  The latter could account for as much as a 50x reduction in
  performance, with the test case from the user with 500 name spaces. A
  more realistic setup on my end with 32 drives showed a 3.5x drop. The
  fix has been thoroughly tested before being committed"

* 'for-linus' of git://git.kernel.dk/linux-block:
  blk-mq: fix performance regression with shared tags
  xen-blkback: don't leak stack data via response ring
  xen/blkback: don't use xen_blkif_get() in xen-blkback kthread
  xen/blkback: don't free be structure too early
  xen/blkback: fix disconnect while I/Os in flight

3 files changed, 26 insertions, 41 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 726c32e35db9..0e824091a12f 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -609,8 +609,6 @@ int xen_blkif_schedule(void *arg)
 	unsigned long timeout;
 	int ret;
 
-	xen_blkif_get(blkif);
-
 	set_freezable();
 	while (!kthread_should_stop()) {
 		if (try_to_freeze())
@@ -665,7 +663,6 @@ purge_gnt_list:
 		print_stats(ring);
 
 	ring->xenblkd = NULL;
-	xen_blkif_put(blkif);
 
 	return 0;
 }
@@ -1436,34 +1433,35 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 static void make_response(struct xen_blkif_ring *ring, u64 id,
 			  unsigned short op, int st)
 {
-	struct blkif_response  resp;
+	struct blkif_response *resp;
 	unsigned long     flags;
 	union blkif_back_rings *blk_rings;
 	int notify;
 
-	resp.id        = id;
-	resp.operation = op;
-	resp.status    = st;
-
 	spin_lock_irqsave(&ring->blk_ring_lock, flags);
 	blk_rings = &ring->blk_rings;
 	/* Place on the response ring for the relevant domain. */
 	switch (ring->blkif->blk_protocol) {
 	case BLKIF_PROTOCOL_NATIVE:
-		memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
-		       &resp, sizeof(resp));
+		resp = RING_GET_RESPONSE(&blk_rings->native,
+					 blk_rings->native.rsp_prod_pvt);
 		break;
 	case BLKIF_PROTOCOL_X86_32:
-		memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
-		       &resp, sizeof(resp));
+		resp = RING_GET_RESPONSE(&blk_rings->x86_32,
+					 blk_rings->x86_32.rsp_prod_pvt);
 		break;
 	case BLKIF_PROTOCOL_X86_64:
-		memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
-		       &resp, sizeof(resp));
+		resp = RING_GET_RESPONSE(&blk_rings->x86_64,
+					 blk_rings->x86_64.rsp_prod_pvt);
 		break;
 	default:
 		BUG();
 	}
+
+	resp->id        = id;
+	resp->operation = op;
+	resp->status    = st;
+
 	blk_rings->common.rsp_prod_pvt++;
 	RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
 	spin_unlock_irqrestore(&ring->blk_ring_lock, flags);
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index dea61f6ab8cb..ecb35fe8ca8d 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -75,9 +75,8 @@ extern unsigned int xenblk_max_queues;
 struct blkif_common_request {
 	char dummy;
 };
-struct blkif_common_response {
-	char dummy;
-};
+
+/* i386 protocol version */
 
 struct blkif_x86_32_request_rw {
 	uint8_t        nr_segments;  /* number of segments                   */
@@ -129,14 +128,6 @@ struct blkif_x86_32_request {
 	} u;
 } __attribute__((__packed__));
 
-/* i386 protocol version */
-#pragma pack(push, 4)
-struct blkif_x86_32_response {
-	uint64_t        id;              /* copied from request */
-	uint8_t         operation;       /* copied from request */
-	int16_t         status;          /* BLKIF_RSP_???       */
-};
-#pragma pack(pop)
 /* x86_64 protocol version */
 
 struct blkif_x86_64_request_rw {
@@ -193,18 +184,12 @@ struct blkif_x86_64_request {
 	} u;
 } __attribute__((__packed__));
 
-struct blkif_x86_64_response {
-	uint64_t       __attribute__((__aligned__(8))) id;
-	uint8_t         operation;       /* copied from request */
-	int16_t         status;          /* BLKIF_RSP_???       */
-};
-
 DEFINE_RING_TYPES(blkif_common, struct blkif_common_request,
-		  struct blkif_common_response);
+		  struct blkif_response);
 DEFINE_RING_TYPES(blkif_x86_32, struct blkif_x86_32_request,
-		  struct blkif_x86_32_response);
+		  struct blkif_response __packed);
 DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request,
-		  struct blkif_x86_64_response);
+		  struct blkif_response);
 
 union blkif_back_rings {
 	struct blkif_back_ring        native;
@@ -281,6 +266,7 @@ struct xen_blkif_ring {
 
 	wait_queue_head_t	wq;
 	atomic_t		inflight;
+	bool			active;
 	/* One thread per blkif ring. */
 	struct task_struct	*xenblkd;
 	unsigned int		waiting_reqs;
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 1f3dfaa54d87..792da683e70d 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -159,7 +159,7 @@ static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
 		init_waitqueue_head(&ring->shutdown_wq);
 		ring->blkif = blkif;
 		ring->st_print = jiffies;
-		xen_blkif_get(blkif);
+		ring->active = true;
 	}
 
 	return 0;
@@ -249,10 +249,12 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 		struct xen_blkif_ring *ring = &blkif->rings[r];
 		unsigned int i = 0;
 
+		if (!ring->active)
+			continue;
+
 		if (ring->xenblkd) {
 			kthread_stop(ring->xenblkd);
 			wake_up(&ring->shutdown_wq);
-			ring->xenblkd = NULL;
 		}
 
 		/* The above kthread_stop() guarantees that at this point we
@@ -296,7 +298,7 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 		BUG_ON(ring->free_pages_num != 0);
 		BUG_ON(ring->persistent_gnt_c != 0);
 		WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
-		xen_blkif_put(blkif);
+		ring->active = false;
 	}
 	blkif->nr_ring_pages = 0;
 	/*
@@ -312,9 +314,10 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 
 static void xen_blkif_free(struct xen_blkif *blkif)
 {
-
-	xen_blkif_disconnect(blkif);
+	WARN_ON(xen_blkif_disconnect(blkif));
 	xen_vbd_free(&blkif->vbd);
+	kfree(blkif->be->mode);
+	kfree(blkif->be);
 
 	/* Make sure everything is drained before shutting down */
 	kmem_cache_free(xen_blkif_cachep, blkif);
@@ -511,8 +514,6 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
 		xen_blkif_put(be->blkif);
 	}
 
-	kfree(be->mode);
-	kfree(be);
 	return 0;
 }