tools/vm/slabinfo: Handle files in debugfs

Commit 64dd68497be76 relocated and renamed the alloc_calls and
free_calls files from /sys/kernel/slab/NAME/*_calls over to
/sys/kernel/debug/slab/NAME/*_calls but didn't update the slabinfo tool
with the new location.

This change will now have slabinfo look at the new location (and filenames)
with a fallback to the prior files.

Fixes: 64dd68497be76 ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
Cc: [e-mail]
Signed-off-by: Stéphane Graber <[e-mail]>
Tested-by: Stéphane Graber <[e-mail]>
Signed-off-by: Vlastimil Babka <[e-mail]>

tools/vm/slabinfo.c

···
 	return l;
 }
 
+static unsigned long read_debug_slab_obj(struct slabinfo *s, const char *name)
+{
+	char x[128];
+	FILE *f;
+	size_t l;
+
+	snprintf(x, 128, "/sys/kernel/debug/slab/%s/%s", s->name, name);
+	f = fopen(x, "r");
+	if (!f) {
+		buffer[0] = 0;
+		l = 0;
+	} else {
+		l = fread(buffer, 1, sizeof(buffer), f);
+		buffer[l] = 0;
+		fclose(f);
+	}
+	return l;
+}
 
 /*
  * Put a size string together
···
 {
 	printf("\n%s: Kernel object allocation\n", s->name);
 	printf("-----------------------------------------------------------------------\n");
-	if (read_slab_obj(s, "alloc_calls"))
+	if (read_debug_slab_obj(s, "alloc_traces"))
+		printf("%s", buffer);
+	else if (read_slab_obj(s, "alloc_calls"))
 		printf("%s", buffer);
 	else
 		printf("No Data\n");
 
 	printf("\n%s: Kernel object freeing\n", s->name);
 	printf("------------------------------------------------------------------------\n");
-	if (read_slab_obj(s, "free_calls"))
+	if (read_debug_slab_obj(s, "free_traces"))
+		printf("%s", buffer);
+	else if (read_slab_obj(s, "free_calls"))
 		printf("%s", buffer);
 	else
 		printf("No Data\n");