linux-kernel - [PATCH v2 3/3] kernel/resource: cleanup and optimize iomem_is

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Date:   Mon, 16 Aug 2021 16:25:05 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     David Hildenbrand <david@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org
Subject: [PATCH v2 3/3] kernel/resource: cleanup and optimize iomem_is_exclusive()

Let's clean it up a bit, reusing for_each_resource() and avoiding
traversing subtrees we are not interested in.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 kernel/resource.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index f57a14617c49..7e59b57afa56 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1759,10 +1759,9 @@ static int strict_iomem_checks;
  */
 bool iomem_is_exclusive(u64 addr)
 {
-	struct resource *p = &iomem_resource;
-	bool err = false;
-	loff_t l;
+	bool skip_children = false, err = false;
 	int size = PAGE_SIZE;
+	struct resource *p;
 
 	if (!strict_iomem_checks)
 		return false;
@@ -1770,15 +1769,19 @@ bool iomem_is_exclusive(u64 addr)
 	addr = addr & PAGE_MASK;
 
 	read_lock(&resource_lock);
-	for (p = p->child; p ; p = r_next(NULL, p, &l)) {
+	for_each_resource(&iomem_resource, p, skip_children) {
 		/*
 		 * We can probably skip the resources without
 		 * IORESOURCE_IO attribute?
 		 */
 		if (p->start >= addr + size)
 			break;
-		if (p->end < addr)
+		if (p->end < addr) {
+			skip_children = true;
 			continue;
+		}
+		skip_children = false;
+
 		/*
 		 * A resource is exclusive if IORESOURCE_EXCLUSIVE is set
 		 * or CONFIG_IO_STRICT_DEVMEM is enabled and the
-- 
2.31.1