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Subject: [PATCH v3 05/23] resource: Report parent to walk_iomem_res_desc()
 callback
From:   Dan Williams <dan.j.williams@intel.com>
To:     akpm@linux-foundation.org
Cc:     Jason Gunthorpe <jgg@mellanox.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Wei Yang <richardw.yang@linux.intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>, peterz@infradead.org,
        vishal.l.verma@intel.com, ard.biesheuvel@linaro.org,
        vishal.l.verma@intel.com, linux-mm@kvack.org,
        linux-nvdimm@lists.01.org, joao.m.martins@oracle.com,
        linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
        dri-devel@lists.freedesktop.org
Date:   Fri, 31 Jul 2020 20:25:29 -0700
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In support of detecting whether a resource might have been been claimed,
report the parent to the walk_iomem_res_desc() callback. For example,
the ACPI HMAT parser publishes "hmem" platform devices per target range.
However, if the HMAT is disabled / missing a fallback driver can attach
devices to the raw memory ranges as a fallback if it sees unclaimed /
orphan "Soft Reserved" resources in the resource tree.

Otherwise, find_next_iomem_res() returns a resource with garbage data
from the stack allocation in __walk_iomem_res_desc() for the res->parent
field.

There are currently no users that expect ->child and ->sibling to be
valid, and the resource_lock would be needed to traverse them. Use a
compound literal to implicitly zero initialize the fields that are not
being returned in addition to setting ->parent.

Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/resource.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 841737bbda9e..f1175ce93a1d 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -382,10 +382,13 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 
 	if (p) {
 		/* copy data */
-		res->start = max(start, p->start);
-		res->end = min(end, p->end);
-		res->flags = p->flags;
-		res->desc = p->desc;
+		*res = (struct resource) {
+			.start = max(start, p->start),
+			.end = min(end, p->end),
+			.flags = p->flags,
+			.desc = p->desc,
+			.parent = p->parent,
+		};
 	}
 
 	read_unlock(&resource_lock);