rust: alloc: implement `contains` for `Flags`

Provide a simple helper function to check whether given flags do
contain one or multiple other flags.

This is used by a subsequent patch implementing the Cmalloc `Allocator`
to check for __GFP_ZERO.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index ee625625bf98..912b6ba2abaa 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -35,7 +35,7 @@ use core::{alloc::Layout, ptr::NonNull};
 /// They can be combined with the operators `|`, `&`, and `!`.
 ///
 /// Values can be used from the [`flags`] module.
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, PartialEq)]
 pub struct Flags(u32);
 
 impl Flags {
@@ -43,6 +43,11 @@ impl Flags {
     pub(crate) fn as_raw(self) -> u32 {
         self.0
     }
+
+    /// Check whether `flags` is contained in `self`.
+    pub fn contains(self, flags: Flags) -> bool {
+        (self & flags) == flags
+    }
 }
 
 impl core::ops::BitOr for Flags {