[PATCH v3 2/8] mm, devm_memremap_pages: Kill mapping "System RAM" support

[Dan Williams]

Given the fact that devm_memremap_pages() requires a percpu_ref that is
torn down by devm_memremap_pages_release() the current support for
mapping RAM is broken.

This has been broken since forever and there is no use case to map RAM
in this way, so just kill the support and make it an explicit error.

Cc: Christoph Hellwig <hch@xxxxxx>
Cc: "JÃrÃme Glisse" <jglisse@xxxxxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 kernel/memremap.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 4478e4688bb7..2d2c901cbe23 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -183,15 +183,12 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	is_ram = region_intersects(align_start, align_size,
 		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
 
-	if (is_ram == REGION_MIXED) {
-		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
-				__func__, res);
+	if (is_ram != REGION_DISJOINT) {
+		WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
+				is_ram == REGION_MIXED ? "mixed" : "ram", res);
 		return ERR_PTR(-ENXIO);
 	}
 
-	if (is_ram == REGION_INTERSECTS)
-		return __va(res->start);
-
 	if (!pgmap->ref)
 		return ERR_PTR(-EINVAL);