[LTP] [PATCH v4] move_mount03: check allow to mount beneath top mount

[Martin Doucha]

Hi,
one note below but this can be merged as is.

Reviewed-by: Martin Doucha <mdoucha@suse.cz>

On 22. 03. 24 12:20, Wei Gao via ltp wrote:
> Signed-off-by: Wei Gao <wegao@suse.com>
> ---
>   include/lapi/fsmount.h                        |   4 +
>   runtest/syscalls                              |   1 +
>   .../kernel/syscalls/move_mount/.gitignore     |   1 +
>   .../kernel/syscalls/move_mount/move_mount03.c | 137 ++++++++++++++++++
>   4 files changed, 143 insertions(+)
>   create mode 100644 testcases/kernel/syscalls/move_mount/move_mount03.c
> 
> diff --git a/include/lapi/fsmount.h b/include/lapi/fsmount.h
> index 07eb42ffa..216e966c7 100644
> --- a/include/lapi/fsmount.h
> +++ b/include/lapi/fsmount.h
> @@ -115,6 +115,10 @@ static inline int mount_setattr(int dirfd, const char *from_pathname, unsigned i
>   }
>   #endif /* HAVE_MOUNT_SETATTR */
>   
> +#ifndef MOVE_MOUNT_BENEATH
> +#define MOVE_MOUNT_BENEATH 		0x00000200
> +#endif /* MOVE_MOUNT_BENEATH */
> +
>   /*
>    * New headers added in kernel after 5.2 release, create them for old userspace.
>   */
> diff --git a/runtest/syscalls b/runtest/syscalls
> index b1125dd75..04b758fd9 100644
> --- a/runtest/syscalls
> +++ b/runtest/syscalls
> @@ -824,6 +824,7 @@ mount_setattr01 mount_setattr01
>   
>   move_mount01 move_mount01
>   move_mount02 move_mount02
> +move_mount03 move_mount03
>   
>   move_pages01 move_pages01
>   move_pages02 move_pages02
> diff --git a/testcases/kernel/syscalls/move_mount/.gitignore b/testcases/kernel/syscalls/move_mount/.gitignore
> index 83ae40145..ddfe10128 100644
> --- a/testcases/kernel/syscalls/move_mount/.gitignore
> +++ b/testcases/kernel/syscalls/move_mount/.gitignore
> @@ -1,2 +1,3 @@
>   /move_mount01
>   /move_mount02
> +/move_mount03
> diff --git a/testcases/kernel/syscalls/move_mount/move_mount03.c b/testcases/kernel/syscalls/move_mount/move_mount03.c
> new file mode 100644
> index 000000000..dfdad080e
> --- /dev/null
> +++ b/testcases/kernel/syscalls/move_mount/move_mount03.c
> @@ -0,0 +1,137 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2023 Christian Brauner <brauner@kernel.org>
> + * Copyright (c) 2023 Wei Gao <wegao@suse.com>
> + */
> +
> +/*\
> + * [Description]
> + *
> + * Test allow to mount beneath top mount feature
> + */
> +
> +/*
> + * Test create for following commit:
> + * commit 6ac392815628f317fcfdca1a39df00b9cc4ebc8b
> + * Author: Christian Brauner <brauner@kernel.org>
> + * Date:   Wed May 3 13:18:42 2023 +0200
> + *     fs: allow to mount beneath top mount
> + *
> + * Above commit has heavily commented but i found following commit
> + * contain simple summary of this feature for easy understanding:
> + *
> + * commit c0a572d9d32fe1e95672f24e860776dba0750a38
> + * Author: Linus Torvalds <torvalds@linux-foundation.org>
> + *       TL;DR:
> + *
> + *         > mount -t ext4 /dev/sda /mnt
> + *           |
> + *           --/mnt    /dev/sda    ext4
> + *
> + *         > mount --beneath -t xfs /dev/sdb /mnt
> + *           |
> + *           --/mnt    /dev/sdb    xfs
> + *             --/mnt  /dev/sda    ext4
> + *
> + *         > umount /mnt
> + *           |
> + *           --/mnt    /dev/sdb    xfs
> + *
> + * So base above scenario design following scenario for LTP check:
> + *
> + *         > mount -t tmpfs /DIRA
> + *           |
> + *           --/DIRA(create A file within DIRA)
> + *
> + *         > mount -t tmpfs /DIRB
> + *           |
> + *           --/DIRA(create B file within DIRB)
> + *
> + *         > move_mount --beneath /DIRA /DIRB
> + *           |
> + *           --/mnt    /DIRA /DIRB
> + *             --/mnt  /DIRB
> + *
> + *         If you check content of /DIRB, you can see file B
> + *
> + *         > umount /DIRB
> + *           |
> + *           --/mnt    /DIRA /DIRB
> + *         Check content of /DIRB, you can see file A exist since
> + *         current /DIRB mount source is already become /DIRA
> + *
> + * See also:
> + * https://lwn.net/Articles/930591/
> + * https://github.com/brauner/move-mount-beneath
> + */
> +
> +#include <stdio.h>
> +
> +#include "tst_test.h"
> +#include "lapi/fsmount.h"
> +#include "lapi/sched.h"
> +
> +#define DIRA "LTP_DIR_A"
> +#define DIRB "LTP_DIR_B"
> +
> +static int fda = -1, fdb = -1;
> +
> +static void run(void)
> +{
> +	SAFE_MOUNT("none", DIRA, "tmpfs", 0, 0);
> +	SAFE_MOUNT("none", DIRB, "tmpfs", 0, 0);
> +	SAFE_TOUCH(DIRA "/A", 0, NULL);
> +	SAFE_TOUCH(DIRB "/B", 0, NULL);
> +
> +	fda = open_tree(AT_FDCWD, DIRA, OPEN_TREE_CLOEXEC | OPEN_TREE_CLONE);
> +	if (fda == -1)
> +		tst_brk(TBROK | TERRNO, "open_tree() failed");
> +
> +	fdb = SAFE_OPEN(DIRB, O_PATH | O_NOFOLLOW, 0666);
> +	TST_EXP_PASS(move_mount(fda, "", fdb, "",
> +				MOVE_MOUNT_BENEATH | MOVE_MOUNT_F_EMPTY_PATH |
> +				MOVE_MOUNT_T_EMPTY_PATH));
> +	SAFE_CLOSE(fda);
> +	SAFE_CLOSE(fdb);
> +
> +	TST_EXP_PASS(access(DIRB "/B", F_OK));

That extra check I've asked for in v3 would still be nice here.

> +	SAFE_UMOUNT(DIRB);
> +	TST_EXP_PASS(access(DIRB "/A", F_OK));
> +
> +	SAFE_UMOUNT(DIRB);
> +	SAFE_UMOUNT(DIRA);
> +}
> +
> +static void setup(void)
> +{
> +	SAFE_MKDIR(DIRA, 0777);
> +	SAFE_MKDIR(DIRB, 0777);
> +}
> +
> +static void cleanup(void)
> +{
> +
> +	if (fda >= 0)
> +		SAFE_CLOSE(fda);
> +
> +	if (fdb >= 0)
> +		SAFE_CLOSE(fdb);
> +
> +	if (tst_is_mounted_at_tmpdir(DIRA))
> +		SAFE_UMOUNT(DIRA);
> +
> +	if (tst_is_mounted_at_tmpdir(DIRB))
> +		SAFE_UMOUNT(DIRB);
> +
> +	if (tst_is_mounted_at_tmpdir(DIRB))
> +		SAFE_UMOUNT(DIRB);
> +}
> +
> +static struct tst_test test = {
> +	.test_all = run,
> +	.needs_root = 1,
> +	.min_kver = "6.5.0",
> +	.needs_tmpdir = 1,
> +	.setup = setup,
> +	.cleanup = cleanup,
> +};

-- 
Martin Doucha   mdoucha@suse.cz
SW Quality Engineer
SUSE LINUX, s.r.o.
CORSO IIa
Krizikova 148/34
186 00 Prague 8
Czech Republic