btrfs: test snapshotting a deleted subvolume

This is a regression test for patch "btrfs: don't abort filesystem when
attempting to snapshot deleted subvolume". Without the fix, the
filesystem goes read-only and prints a warning. With the fix, it should
fail gracefully with ENOENT.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>

5 files changed, 133 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index 7508b6e8b2..5cc3a5e4ae 100644
--- a/.gitignore
+++ b/.gitignore
@@ -166,6 +166,7 @@ tags
 /src/t_readdir_2
 /src/t_readdir_3
 /src/t_rename_overwrite
+/src/t_snapshot_deleted_subvolume
 /src/t_stripealign
 /src/t_truncate_cmtime
 /src/t_truncate_self
diff --git a/src/Makefile b/src/Makefile
index d79015cef4..e7442487bc 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -34,7 +34,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
 	fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \
 	detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \
-	uuid_ioctl
+	uuid_ioctl t_snapshot_deleted_subvolume
 
 EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
 	      btrfs_crc32c_forged_name.py popdir.pl popattr.py \
diff --git a/src/t_snapshot_deleted_subvolume.c b/src/t_snapshot_deleted_subvolume.c
new file mode 100644
index 0000000000..c3adb1c438
--- /dev/null
+++ b/src/t_snapshot_deleted_subvolume.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) Meta Platforms, Inc. and affiliates.
+
+#include "global.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <linux/types.h>
+#ifdef HAVE_STRUCT_BTRFS_IOCTL_VOL_ARGS_V2
+#include <linux/btrfs.h>
+#else
+#ifndef BTRFS_IOCTL_MAGIC
+#define BTRFS_IOCTL_MAGIC 0x94
+#endif
+
+#ifndef BTRFS_IOC_SNAP_DESTROY_V2
+#define BTRFS_IOC_SNAP_DESTROY_V2 \
+	_IOW(BTRFS_IOCTL_MAGIC, 63, struct btrfs_ioctl_vol_args_v2)
+#endif
+
+#ifndef BTRFS_IOC_SNAP_CREATE_V2
+#define BTRFS_IOC_SNAP_CREATE_V2 \
+	_IOW(BTRFS_IOCTL_MAGIC, 23, struct btrfs_ioctl_vol_args_v2)
+#endif
+
+#ifndef BTRFS_IOC_SUBVOL_CREATE_V2
+#define BTRFS_IOC_SUBVOL_CREATE_V2 \
+	_IOW(BTRFS_IOCTL_MAGIC, 24, struct btrfs_ioctl_vol_args_v2)
+#endif
+
+#ifndef BTRFS_SUBVOL_NAME_MAX
+#define BTRFS_SUBVOL_NAME_MAX 4039
+#endif
+
+struct btrfs_ioctl_vol_args_v2 {
+	__s64 fd;
+	__u64 transid;
+	__u64 flags;
+	union {
+		struct {
+			__u64 size;
+			struct btrfs_qgroup_inherit *qgroup_inherit;
+		};
+		__u64 unused[4];
+	};
+	union {
+		char name[BTRFS_SUBVOL_NAME_MAX + 1];
+		__u64 devid;
+		__u64 subvolid;
+	};
+};
+#endif
+
+int main(int argc, char **argv)
+{
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s PATH\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	int dirfd = open(argv[1], O_RDONLY | O_DIRECTORY);
+	if (dirfd < 0) {
+		perror(argv[1]);
+		return EXIT_FAILURE;
+	}
+
+	struct btrfs_ioctl_vol_args_v2 subvol_args = {};
+	strcpy(subvol_args.name, "subvol");
+	if (ioctl(dirfd, BTRFS_IOC_SUBVOL_CREATE_V2, &subvol_args) < 0) {
+		perror("BTRFS_IOC_SUBVOL_CREATE_V2");
+		return EXIT_FAILURE;
+	}
+
+	int subvolfd = openat(dirfd, "subvol", O_RDONLY | O_DIRECTORY);
+	if (subvolfd < 0) {
+		perror("openat");
+		return EXIT_FAILURE;
+	}
+
+	if (ioctl(dirfd, BTRFS_IOC_SNAP_DESTROY_V2, &subvol_args) < 0) {
+		perror("BTRFS_IOC_SNAP_DESTROY_V2");
+		return EXIT_FAILURE;
+	}
+
+	struct btrfs_ioctl_vol_args_v2 snap_args = { .fd = subvolfd };
+	strcpy(snap_args.name, "snap");
+	if (ioctl(dirfd, BTRFS_IOC_SNAP_CREATE_V2, &snap_args) < 0) {
+		if (errno == ENOENT)
+			return EXIT_SUCCESS;
+		perror("BTRFS_IOC_SNAP_CREATE_V2");
+		return EXIT_FAILURE;
+	}
+	fprintf(stderr, "BTRFS_IOC_SNAP_CREATE_V2 should've failed\n");
+	return EXIT_FAILURE;
+}
diff --git a/tests/btrfs/309 b/tests/btrfs/309
new file mode 100755
index 0000000000..5cbcd22382
--- /dev/null
+++ b/tests/btrfs/309
@@ -0,0 +1,27 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# FS QA Test 309
+#
+# Try to snapshot a deleted subvolume.
+#
+. ./common/preamble
+_begin_fstest auto quick snapshot subvol
+
+_supported_fs btrfs
+_require_scratch
+_require_test_program t_snapshot_deleted_subvolume
+_fixed_by_kernel_commit XXXXXXXXXXXX \
+	"btrfs: don't abort filesystem when attempting to snapshot deleted subvolume"
+
+_scratch_mkfs >> $seqres.full 2>&1 || _fail "mkfs failed"
+_scratch_mount
+
+"$here/src/t_snapshot_deleted_subvolume" "$SCRATCH_MNT"
+# Make sure the filesystem didn't go read-only.
+touch "$SCRATCH_MNT/foo"
+
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/btrfs/309.out b/tests/btrfs/309.out
new file mode 100644
index 0000000000..56330d6540
--- /dev/null
+++ b/tests/btrfs/309.out
@@ -0,0 +1,2 @@
+QA output created by 309
+Silence is golden