mm: Fix bugs in region_is_ram()

region_is_ram() looks up the iomem_resource table to check if
a target range is in RAM.  However, it always returns with -1
due to invalid range checks. It always breaks the loop at the
first entry of the table.

Another issue is that it compares p->flags and flags, but it always
fails. flags is declared as int, which makes it as a negative value
with IORESOURCE_BUSY (0x80000000) set while p->flags is unsigned long.

Fix the range check and flags so that region_is_ram() works as
advertised.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Mike Travis <travis@sgi.com>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Roland Dreier <roland@purestorage.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1437088996-28511-4-git-send-email-toshi.kani@hp.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/resource.c

@@ -504,13 +504,13 @@ int region_is_ram(resource_size_t start, unsigned long size)
 {
 	struct resource *p;
 	resource_size_t end = start + size - 1;
-	int flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 	const char *name = "System RAM";
 	int ret = -1;
 
 	read_lock(&resource_lock);
 	for (p = iomem_resource.child; p ; p = p->sibling) {
-		if (end < p->start)
+		if (p->end < start)
 			continue;
 
 		if (p->start <= start && end <= p->end) {
@@ -521,7 +521,7 @@ int region_is_ram(resource_size_t start, unsigned long size)
 				ret = 1;
 			break;
 		}
-		if (p->end < start)
+		if (end < p->start)
 			break;	/* not found */
 	}
 	read_unlock(&resource_lock);