proc/vmcore: let pfn_is_ram() return a bool

The callback should deal with errors internally, it doesn't make sense
to expose these via pfn_is_ram().  We'll rework the callbacks next.
Right now we consider errors as if "it's RAM"; no functional change.

Link: https://lkml.kernel.org/r/20211005121430.30136-5-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/vmcore.c

@@ -84,11 +84,11 @@ void unregister_oldmem_pfn_is_ram(void)
 }
 EXPORT_SYMBOL_GPL(unregister_oldmem_pfn_is_ram);
 
-static int pfn_is_ram(unsigned long pfn)
+static bool pfn_is_ram(unsigned long pfn)
 {
 	int (*fn)(unsigned long pfn);
 	/* pfn is ram unless fn() checks pagetype */
-	int ret = 1;
+	bool ret = true;
 
 	/*
 	 * Ask hypervisor if the pfn is really ram.
@@ -97,7 +97,7 @@ static int pfn_is_ram(unsigned long pfn)
 	 */
 	fn = oldmem_pfn_is_ram;
 	if (fn)
-		ret = fn(pfn);
+		ret = !!fn(pfn);
 
 	return ret;
 }
@@ -124,7 +124,7 @@ ssize_t read_from_oldmem(char *buf, size_t count,
 			nr_bytes = count;
 
 		/* If pfn is not ram, return zeros for sparse dump files */
-		if (pfn_is_ram(pfn) == 0)
+		if (!pfn_is_ram(pfn))
 			memset(buf, 0, nr_bytes);
 		else {
 			if (encrypted)