From: wguanghao <wuguanghao3@huawei.com>
Date: Mon, 22 Sep 2025 14:58:49 +0000 (+0800)
Subject: losetup: Add the --remove/-R parameter to remove loop devices
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ac42e0a8595c34e6da2778d5374f6cd7004f89a3;p=thirdparty%2Futil-linux.git

losetup: Add the --remove/-R parameter to remove loop devices

Signed-off-by: Wu Guanghao <wuguanghao3@huawei.com>
---

diff --git a/include/loopdev.h b/include/loopdev.h
index 396ade264..d5ef85107 100644
--- a/include/loopdev.h
+++ b/include/loopdev.h
@@ -186,6 +186,7 @@ extern int loopcxt_next(struct loopdev_cxt *lc);
 
 extern int loopcxt_setup_device(struct loopdev_cxt *lc);
 extern int loopcxt_detach_device(struct loopdev_cxt *lc);
+extern int loopcxt_remove_device(struct loopdev_cxt *lc);
 
 extern int loopcxt_ioctl_status(struct loopdev_cxt *lc);
 extern int loopcxt_ioctl_capacity(struct loopdev_cxt *lc);
diff --git a/lib/loopdev.c b/lib/loopdev.c
index 4836a3ab5..a32003d4b 100644
--- a/lib/loopdev.c
+++ b/lib/loopdev.c
@@ -1622,6 +1622,37 @@ int loopcxt_detach_device(struct loopdev_cxt *lc)
 	return 0;
 }
 
+int loopcxt_remove_device(struct loopdev_cxt *lc)
+{
+       int rc = -EINVAL;
+       int ctl, nr = -1;
+       const char *p, *dev = loopcxt_get_device(lc);
+
+       if (!dev)
+               goto done;
+
+       if (!(lc->flags & LOOPDEV_FL_CONTROL)) {
+               rc = -ENOSYS;
+               goto done;
+       }
+
+       p = strrchr(dev, '/');
+       if (!p || (sscanf(p, "/loop%d", &nr) != 1 && sscanf(p, "/%d", &nr) != 1)
+              || nr < 0)
+               goto done;
+
+       ctl = open(_PATH_DEV_LOOPCTL, O_RDWR|O_CLOEXEC);
+       if (ctl >= 0) {
+               DBG(CXT, ul_debugobj(lc, "remove_device %d", nr));
+               rc = ioctl(ctl, LOOP_CTL_REMOVE, nr);
+               close(ctl);
+       }
+       lc->control_ok = rc >= 0 ? 1 : 0;
+done:
+       DBG(CXT, ul_debugobj(lc, "remove_device done [rc=%d]", rc));
+       return rc;
+}
+
 int loopcxt_add_device(struct loopdev_cxt *lc)
 {
 	int rc = -EINVAL;
diff --git a/sys-utils/losetup.8.adoc b/sys-utils/losetup.8.adoc
index 48d71ec18..4437088b8 100644
--- a/sys-utils/losetup.8.adoc
+++ b/sys-utils/losetup.8.adoc
@@ -36,6 +36,10 @@ Resize a loop device:
 
 *losetup* *-c* _loopdev_
 
+Remove a loop device:
+
+*losetup* *-R* _loopdev_ ...
+
 == DESCRIPTION
 
 *losetup* is used to associate loop devices with regular files or block devices, to detach loop devices, and to query the status of a loop device. If only the _loopdev_ argument is given, the status of the corresponding loop device is shown. If no option is given, all loop devices are shown.
@@ -123,6 +127,12 @@ Use the raw *--list* output format.
 *-J*, *--json*::
 Use JSON format for *--list* output.
 
+*-R*, *--remove* _loopdev_...::
+The parameter is not recommended for direct use.
+*-d* or *-D* option to disconnect the file from the loop device, we can see a loop device
+of size 0 by running 'lsblk -a'. At this point, the loop device will still in the system.
+This parameter can truly remove the loop device, and there is no command or interface to view it.
+
 include::man-common/help-version.adoc[]
 
 == ENCRYPTION
diff --git a/sys-utils/losetup.c b/sys-utils/losetup.c
index efda75c03..faab3934b 100644
--- a/sys-utils/losetup.c
+++ b/sys-utils/losetup.c
@@ -46,6 +46,7 @@ enum {
 	A_SET_CAPACITY,		/* set device capacity */
 	A_SET_DIRECT_IO,	/* set accessing backing file by direct io */
 	A_SET_BLOCKSIZE,	/* set logical block size of the loop device */
+	A_REMOVE,       /* remove given device */
 };
 
 enum {
@@ -259,6 +260,13 @@ static int detach_all_loops(struct loopdev_cxt *lc)
 	return res;
 }
 
+static int remove_loop(struct loopdev_cxt *lc)
+{
+    if (loopcxt_remove_device(lc))
+        return -1;
+    return 0;
+}
+
 static int set_scols_data(struct loopdev_cxt *lc, struct libscols_line *ln)
 {
 	size_t i;
@@ -479,6 +487,7 @@ static void __attribute__((__noreturn__)) usage(void)
 	fputs(_(" -c, --set-capacity <loopdev>  resize the device\n"), out);
 	fputs(_(" -j, --associated <file>       list all devices associated with <file>\n"), out);
 	fputs(_(" -L, --nooverlap               avoid possible conflict between devices\n"), out);
+	fputs(_(" -R, --remove <loopdev>...     remove one or more devices\n"), out);
 
 	/* commands options */
 	fputs(USAGE_SEPARATOR, out);
@@ -720,6 +729,7 @@ int main(int argc, char **argv)
 		{ "show",         no_argument,       NULL, OPT_SHOW      },
 		{ "verbose",      no_argument,       NULL, 'v'           },
 		{ "version",      no_argument,       NULL, 'V'           },
+		{ "remove",       required_argument, NULL, 'R'           },
 		{ NULL, 0, NULL, 0 }
 	};
 
@@ -740,7 +750,7 @@ int main(int argc, char **argv)
 	if (loopcxt_init(&lc, 0))
 		err(EXIT_FAILURE, _("failed to initialize loopcxt"));
 
-	while ((c = getopt_long(argc, argv, "ab:c:d:Dfhj:JlLno:O:PrvV",
+	while ((c = getopt_long(argc, argv, "ab:c:d:Dfhj:JlLno:O:PrvVR:",
 				longopts, NULL)) != -1) {
 
 		err_exclusive_options(c, longopts, excl, excl_st);
@@ -834,6 +844,13 @@ int main(int argc, char **argv)
 		case 'V':
 			print_version(EXIT_SUCCESS);
 
+		case 'R':
+			act = A_REMOVE;
+			if (loopcxt_set_device(&lc, optarg))
+				err(EXIT_FAILURE, _("%s: failed to use device"),
+						optarg);
+			break;
+
 		default:
 			errtryhelp(EXIT_FAILURE);
 		}
@@ -995,6 +1012,18 @@ int main(int argc, char **argv)
 			warn(_("%s: set logical block size failed"),
 			        loopcxt_get_device(&lc));
 		break;
+
+	case A_REMOVE:
+		res = remove_loop(&lc);
+		while (optind < argc) {
+			if (loopcxt_set_device(&lc, argv[optind]))
+				warn(_("%s: failed to use device"),
+						argv[optind]);
+			optind++;
+			res += remove_loop(&lc);
+		}
+		break;
+
 	default:
 		warnx(_("bad usage"));
 		errtryhelp(EXIT_FAILURE);