fs: add attr_flags_to_mnt_flags helper

Add a simple helper to translate uapi MOUNT_ATTR_* flags to MNT_* flags
which we will use in follow-up patches too.

Link: https://lore.kernel.org/r/20210121131959.646623-34-christian.brauner@ubuntu.com
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/fs/namespace.c b/fs/namespace.c
index 774ae5f74716772204a59e9dbfa4de8f0ece5893..00ed0d6cb2ee08d41a77bb0137610f3eebe77cbb 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3465,6 +3465,28 @@ out_type:
        return ret;
 }
 
+#define FSMOUNT_VALID_FLAGS \
+       (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
+        MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME)
+
+static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
+{
+       unsigned int mnt_flags = 0;
+
+       if (attr_flags & MOUNT_ATTR_RDONLY)
+               mnt_flags |= MNT_READONLY;
+       if (attr_flags & MOUNT_ATTR_NOSUID)
+               mnt_flags |= MNT_NOSUID;
+       if (attr_flags & MOUNT_ATTR_NODEV)
+               mnt_flags |= MNT_NODEV;
+       if (attr_flags & MOUNT_ATTR_NOEXEC)
+               mnt_flags |= MNT_NOEXEC;
+       if (attr_flags & MOUNT_ATTR_NODIRATIME)
+               mnt_flags |= MNT_NODIRATIME;
+
+       return mnt_flags;
+}
+
 /*
  * Create a kernel mount representation for a new, prepared superblock
  * (specified by fs_fd) and attach to an open_tree-like file descriptor.
@@ -3487,24 +3509,10 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
        if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
                return -EINVAL;
 
-       if (attr_flags & ~(MOUNT_ATTR_RDONLY |
-                          MOUNT_ATTR_NOSUID |
-                          MOUNT_ATTR_NODEV |
-                          MOUNT_ATTR_NOEXEC |
-                          MOUNT_ATTR__ATIME |
-                          MOUNT_ATTR_NODIRATIME))
+       if (attr_flags & ~FSMOUNT_VALID_FLAGS)
                return -EINVAL;
 
-       if (attr_flags & MOUNT_ATTR_RDONLY)
-               mnt_flags |= MNT_READONLY;
-       if (attr_flags & MOUNT_ATTR_NOSUID)
-               mnt_flags |= MNT_NOSUID;
-       if (attr_flags & MOUNT_ATTR_NODEV)
-               mnt_flags |= MNT_NODEV;
-       if (attr_flags & MOUNT_ATTR_NOEXEC)
-               mnt_flags |= MNT_NOEXEC;
-       if (attr_flags & MOUNT_ATTR_NODIRATIME)
-               mnt_flags |= MNT_NODIRATIME;
+       mnt_flags = attr_flags_to_mnt_flags(attr_flags);
 
        switch (attr_flags & MOUNT_ATTR__ATIME) {
        case MOUNT_ATTR_STRICTATIME: