[PATCH 12/17] fsinfo: Allow the mount topology propogation flags to be retrieved [ver #17]

David Howells
2020-02-21T18:03:35Z

Allow the mount topology propogation flags to be retrieved as part of the
FSINFO_ATTR_MOUNT_INFO attributes.

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/namespace.c | 7 ++++++-
include/uapi/linux/fsinfo.h | 2 +-
include/uapi/linux/mount.h | 10 +++++++++-
samples/vfs/test-fsinfo.c | 1 +
samples/vfs/test-mntinfo.c | 8 ++++----
5 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index fc22aea18e2d..bbfd6cd5c501 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4142,15 +4142,20 @@ int fsinfo_generic_mount_info(struct path *path, struct fsinfo_context *ctx)
p->parent_id = p->mnt_id;
rcu_read_unlock();
}
- if (IS_MNT_SHARED(m))
+ if (IS_MNT_SHARED(m)) {
p->group_id = m->mnt_group_id;
+ p->propagation |= MOUNT_PROPAGATION_SHARED;
+ }
if (IS_MNT_SLAVE(m)) {
int master = m->mnt_master->mnt_group_id;
int dom = get_dominating_id(m, &root);
p->master_id = master;
if (dom && dom != master)
p->from_id = dom;
+ p->propagation |= MOUNT_PROPAGATION_SLAVE;
}
+ if (IS_MNT_UNBINDABLE(m))
+ p->propagation |= MOUNT_PROPAGATION_UNBINDABLE;
path_put(&root);

flags = READ_ONCE(m->mnt.mnt_flags);
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 29940d110ce3..119c371697be 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -100,7 +100,7 @@ struct fsinfo_mount_info {
__u32 from_id; /* Slave propagated from ID */
__u32 attr; /* MOUNT_ATTR_* flags */
__u32 change_counter; /* Number of changes applied. */
- __u32 __reserved[1];
+ __u32 propagation; /* MOUNT_PROPAGATION_* flags */
};

#define FSINFO_ATTR_MOUNT_INFO__STRUCT struct fsinfo_mount_info
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 96a0240f23fe..39e50fe9d8d9 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -105,7 +105,7 @@ enum fsconfig_command {
#define FSMOUNT_CLOEXEC 0x00000001

/*
- * Mount attributes.
+ * Mount object attributes (these are separate to filesystem attributes).
*/
#define MOUNT_ATTR_RDONLY 0x00000001 /* Mount read-only */
#define MOUNT_ATTR_NOSUID 0x00000002 /* Ignore suid and sgid bits */
@@ -117,4 +117,12 @@ enum fsconfig_command {
#define MOUNT_ATTR_STRICTATIME 0x00000020 /* - Always perform atime updates */
#define MOUNT_ATTR_NODIRATIME 0x00000080 /* Do not update directory access times */

+/*
+ * Mount object propogation attributes.
+ */
+#define MOUNT_PROPAGATION_UNBINDABLE 0x00000001 /* Mount is unbindable */
+#define MOUNT_PROPAGATION_SLAVE 0x00000002 /* Mount is slave */
+#define MOUNT_PROPAGATION_PRIVATE 0x00000000 /* Mount is private (ie. not shared) */
+#define MOUNT_PROPAGATION_SHARED 0x00000004 /* Mount is shared */
+
#endif /* _UAPI_LINUX_MOUNT_H */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index f761ded6a52c..6a61f3426982 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -291,6 +291,7 @@ static void dump_fsinfo_generic_mount_info(void *reply, unsigned int size)
printf("\tmnt_id : %x\n", f->mnt_id);
printf("\tparent : %x\n", f->parent_id);
printf("\tgroup : %x\n", f->group_id);
+ printf("\tpropag : %x\n", f->propagation);
printf("\tattr : %x\n", f->attr);
printf("\tchanges : %x\n", f->change_counter);
}
diff --git a/samples/vfs/test-mntinfo.c b/samples/vfs/test-mntinfo.c
index f4d90d0671c5..5a3d6b917447 100644
--- a/samples/vfs/test-mntinfo.c
+++ b/samples/vfs/test-mntinfo.c
@@ -135,9 +135,9 @@ static void display_mount(unsigned int mnt_id, unsigned int depth, char *path)
printf("%*.*s", s, s, "");

sprintf(dev, "%x:%x", ids.f_dev_major, ids.f_dev_minor);
- printf("%10u %8x %2x %5s %s",
+ printf("%10u %8x %2x %x %5s %s",
info.mnt_id, info.change_counter,
- info.attr,
+ info.attr, info.propagation,
dev, ids.f_fs_name);
putchar('\n');

@@ -236,8 +236,8 @@ int main(int argc, char **argv)
exit(2);
}

- printf("MOUNT MOUNT ID CHANGE# AT DEV TYPE\n");
- printf("------------------------------------- ---------- -------- -- ----- --------\n");
+ printf("MOUNT MOUNT ID CHANGE# AT P DEV TYPE\n");
+ printf("------------------------------------- ---------- -------- -- - ----- --------\n");
display_mount(mnt_id, 0, path);
return 0;
}