linux-kernel - [PATCH v3 1/4] resource: Change __request_region to inherit from immediate parent

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Date:	Wed,  9 Mar 2016 12:47:03 -0700
From:	Toshi Kani <toshi.kani@....com>
To:	mingo@...nel.org, bp@...e.de, dan.j.williams@...el.com,
	rjw@...ysocki.net, akpm@...ux-foundation.org
Cc:	linux-nvdimm@...ts.01.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, Toshi Kani <toshi.kani@....com>
Subject: [PATCH v3 1/4] resource: Change __request_region to inherit from immediate parent

__request_region() sets 'flags' of a new resource from @parent
as it inherits the parent's attribute.  When a target resource
has a conflict, this function inserts the new resource entry
under the conflicted entry by updating @parent.  In this case,
the new resource entry needs to inherit attribute from the updated
parent.  This conflict is a typical case since __request_region()
is used to allocate a new resource from a specific resource range.

For instance, request_mem_region() calls __request_region() with
@parent set to &iomem_resource, which is the root entry of the
whole iomem range.  When this request results in inserting a new
entry "DEV-A" under "BUS-1", "DEV-A" needs to inherit from the
immediate parent "BUS-1" as it holds specific attribute for the
range.

root (&iomem_resource)
 :
 + "BUS-1"
    + "DEV-A"

Change __request_region() to set 'flags' and 'desc' of a new entry
from the immediate parent.

Signed-off-by: Toshi Kani <toshi.kani@....com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dan Williams <dan.j.williams@...el.com>
---
 kernel/resource.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 4d46605..5a56e8f 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1085,15 +1085,16 @@ struct resource * __request_region(struct resource *parent,
 	res->name = name;
 	res->start = start;
 	res->end = start + n - 1;
-	res->flags = resource_type(parent) | resource_ext_type(parent);
-	res->flags |= IORESOURCE_BUSY | flags;
-	res->desc = IORES_DESC_NONE;

 	write_lock(&resource_lock);

 	for (;;) {
 		struct resource *conflict;

+		res->flags = resource_type(parent) | resource_ext_type(parent);
+		res->flags |= IORESOURCE_BUSY | flags;
+		res->desc = parent->desc;
+
 		conflict = __request_resource(parent, res);
 		if (!conflict)
 			break;