ft-lib: add discard()

ft-lib/dm-ioctl.c

@@ -487,8 +487,6 @@ int dm_load(struct dm_interface *dmi, const char *name,
 	return r;
 }
 
-//----------------------------------------------------------------
-// returns false if control buffer too small.
 static bool get_status(struct dm_interface *dmi, struct dm_ioctl *ctl,
 		       const char *name, unsigned flags,
 		       int *result)
@@ -611,4 +609,24 @@ int get_dev_size(const char *path, uint64_t *sectors)
 	return r;
 }
 
+int discard(const char *path, uint64_t sector_b, uint64_t sector_e)
+{
+	int r, fd;
+	uint64_t payload[2];
+
+	fd = open(path, O_RDWR);
+	if (fd < 0) {
+        	fprintf(stderr, "couldn't open %s", path);
+		return -EINVAL;
+	}
+
+	payload[0] = sector_b;
+	payload[1] = sector_e;
+
+	r = ioctl(fd, BLKDISCARD, payload);
+	close(fd);
+
+	return r;
+}
+
 //----------------------------------------------------------------

functional-tests/device-mapper/ioctl.scm

@@ -44,7 +44,8 @@
 
           message
 
-          get-dev-size)
+          get-dev-size
+          discard)
 
   (import (chezscheme)
           (disk-units)
@@ -393,4 +394,10 @@
            (if (zero? r)
                (sectors result)
                (fail (fmt #f "get-dev-size failed: " r))))))
+
+  (define (discard dev sb se)
+    (define c-discard
+      (foreign-procedure "discard" (string unsigned-64 unsigned-64) int))
+    (unless (zero? (c-discard dev sb se))
+            (fail (fmt #f "discard ioctl failed"))))
 )