libnvdimm, pmem: move request_queue allocation earlier in probe

Before the dynamically allocated struct pages from devm_memremap_pages()
can be put to use outside the driver, we need a mechanism to track
whether they are still in use at teardown.  Towards that goal reorder
the initialization sequence to allow the 'q_usage_counter' from the
request_queue to be used by the devm_memremap_pages() implementation (in
subsequent patches).

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/nvdimm/pmem.c

@@ -159,6 +159,7 @@ static struct pmem_device *pmem_alloc(struct device *dev,
 		struct resource *res, int id)
 {
 	struct pmem_device *pmem;
+	struct request_queue *q;
 
 	pmem = devm_kzalloc(dev, sizeof(*pmem), GFP_KERNEL);
 	if (!pmem)
@@ -176,6 +177,10 @@ static struct pmem_device *pmem_alloc(struct device *dev,
 		return ERR_PTR(-EBUSY);
 	}
 
+	q = blk_alloc_queue_node(GFP_KERNEL, dev_to_node(dev));
+	if (!q)
+		return ERR_PTR(-ENOMEM);
+
 	pmem->pfn_flags = PFN_DEV;
 	if (pmem_should_map_pages(dev)) {
 		pmem->virt_addr = (void __pmem *) devm_memremap_pages(dev, res,
@@ -186,9 +191,12 @@ static struct pmem_device *pmem_alloc(struct device *dev,
 				pmem->phys_addr, pmem->size,
 				ARCH_MEMREMAP_PMEM);
 
-	if (IS_ERR(pmem->virt_addr))
+	if (IS_ERR(pmem->virt_addr)) {
+		blk_cleanup_queue(q);
 		return (void __force *) pmem->virt_addr;
+	}
 
+	pmem->pmem_queue = q;
 	return pmem;
 }
 
@@ -208,10 +216,6 @@ static int pmem_attach_disk(struct device *dev,
 	int nid = dev_to_node(dev);
 	struct gendisk *disk;
 
-	pmem->pmem_queue = blk_alloc_queue_node(GFP_KERNEL, nid);
-	if (!pmem->pmem_queue)
-		return -ENOMEM;
-
 	blk_queue_make_request(pmem->pmem_queue, pmem_make_request);
 	blk_queue_physical_block_size(pmem->pmem_queue, PAGE_SIZE);
 	blk_queue_max_hw_sectors(pmem->pmem_queue, UINT_MAX);
@@ -446,19 +450,22 @@ static int nd_pmem_probe(struct device *dev)
 		return -ENOMEM;
 	nvdimm_namespace_add_poison(ndns, &pmem->bb, 0);
 
-	if (is_nd_btt(dev))
+	if (is_nd_btt(dev)) {
+		/* btt allocates its own request_queue */
+		blk_cleanup_queue(pmem->pmem_queue);
+		pmem->pmem_queue = NULL;
 		return nvdimm_namespace_attach_btt(ndns);
+	}
 
 	if (is_nd_pfn(dev))
 		return nvdimm_namespace_attach_pfn(ndns);
 
-	if (nd_btt_probe(ndns, pmem) == 0) {
-		/* we'll come back as btt-pmem */
-		return -ENXIO;
-	}
-
-	if (nd_pfn_probe(ndns, pmem) == 0) {
-		/* we'll come back as pfn-pmem */
+	if (nd_btt_probe(ndns, pmem) == 0 || nd_pfn_probe(ndns, pmem) == 0) {
+		/*
+		 * We'll come back as either btt-pmem, or pfn-pmem, so
+		 * drop the queue allocation for now.
+		 */
+		blk_cleanup_queue(pmem->pmem_queue);
 		return -ENXIO;
 	}