From a597bc04de8990dc66e9641c782d6a9fc80a5abe Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mssola@mssola.com>
Date: Tue, 24 Feb 2026 00:17:26 +0100
Subject: btrfs: add examples on the shutdown experimental feature
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Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
---
 fs/btrfs/shutdown/shutdown.c | 68 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 fs/btrfs/shutdown/shutdown.c

(limited to 'fs/btrfs/shutdown/shutdown.c')

diff --git a/fs/btrfs/shutdown/shutdown.c b/fs/btrfs/shutdown/shutdown.c
new file mode 100644
index 0000000..46a5731
--- /dev/null
+++ b/fs/btrfs/shutdown/shutdown.c
@@ -0,0 +1,68 @@
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <linux/btrfs.h>
+#include <linux/magic.h>
+#include <linux/types.h>
+#include <sys/ioctl.h>
+#include <sys/statfs.h>
+
+/*
+ * Constants defined in BTRFS' experimental shutdown support
+ * starting from Linux 6.19.
+ */
+
+#ifndef BTRFS_SHUTDOWN_FLAGS_DEFAULT
+#define BTRFS_SHUTDOWN_FLAGS_DEFAULT	0x0
+#endif
+
+#ifndef BTRFS_IOC_SHUTDOWN
+#define BTRFS_IOC_SHUTDOWN	_IOR('X', 125, __u32)
+#endif
+
+int main(int argc, char *argv[])
+{
+	int fd;
+	__u32 flags;
+	struct statfs info;
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <mount point>\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	if (statfs(argv[1], &info) == 0) {
+		/*
+		 * We could certainly use this ioctl against EXT4 or XFS, but that's not
+		 * the point we want to illustrate here.
+		 */
+		if (info.f_type != BTRFS_SUPER_MAGIC) {
+			printf("error: you are supposed to be running this against BTRFS;"
+				   " %lx magic detected instead\n", info.f_type);
+			exit(EXIT_FAILURE);
+		}
+	} else {
+		perror("statfs failed");
+		exit(EXIT_FAILURE);
+	}
+
+	fd = open(argv[1], O_RDONLY | O_DIRECTORY);
+	if (fd < 0) {
+	    perror("open");
+		exit(EXIT_FAILURE);
+	}
+
+	flags = BTRFS_SHUTDOWN_FLAGS_DEFAULT;
+	if (ioctl(fd, BTRFS_IOC_SHUTDOWN, &flags) == 0) {
+	    printf("Success: filesystem shut down.\n");
+	} else {
+	    perror("Shutdown failed");
+		exit(EXIT_FAILURE);
+	}
+
+	close(fd);
+	return 0;
+}
-- 
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