linux-kernel - [PATCH v4 2/8] mm, devm_memremap_pages: Kill mapping "System RAM" support

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Date:   Tue, 10 Jul 2018 22:14:48 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     akpm@...ux-foundation.org
Cc:     Christoph Hellwig <hch@....de>,
        Jérôme Glisse <jglisse@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/8] mm,
 devm_memremap_pages: Kill mapping "System RAM" support

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.

Support for remapping "System RAM" has been broken since the beginning
and there is no existing user of this this code path, so just kill the
support and make it an explicit error.

This cleanup also simplifies a follow-on patch to fix the error path
when setting a devm release action for devm_memremap_pages_release()
fails.

Cc: Christoph Hellwig <hch@....de>
Cc: "Jérôme Glisse" <jglisse@...hat.com>
Cc: Logan Gunthorpe <logang@...tatee.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 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);