From 98d2b43081972abeb5bb5a087bc3e3197531c46e Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 25 Oct 2023 16:01:59 +0200 Subject: add unique mount ID If a mount is released then its mnt_id can immediately be reused. This is bad news for user interfaces that want to uniquely identify a mount. Implementing a unique mount ID is trivial (use a 64bit counter). Unfortunately userspace assumes 32bit size and would overflow after the counter reaches 2^32. Introduce a new 64bit ID alongside the old one. Initialize the counter to 2^32, this guarantees that the old and new IDs are never mixed up. Signed-off-by: Miklos Szeredi Link: https://lore.kernel.org/r/20231025140205.3586473-2-mszeredi@redhat.com Reviewed-by: Ian Kent Signed-off-by: Christian Brauner --- fs/stat.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'fs/stat.c') diff --git a/fs/stat.c b/fs/stat.c index 24bb0209e459..e44f0625c24f 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -243,8 +243,13 @@ retry: error = vfs_getattr(&path, stat, request_mask, flags); - stat->mnt_id = real_mount(path.mnt)->mnt_id; - stat->result_mask |= STATX_MNT_ID; + if (request_mask & STATX_MNT_ID_UNIQUE) { + stat->mnt_id = real_mount(path.mnt)->mnt_id_unique; + stat->result_mask |= STATX_MNT_ID_UNIQUE; + } else { + stat->mnt_id = real_mount(path.mnt)->mnt_id; + stat->result_mask |= STATX_MNT_ID; + } if (path.mnt->mnt_root == path.dentry) stat->attributes |= STATX_ATTR_MOUNT_ROOT; -- cgit