On Thu, 25 Jul 2024 14:27:39 +0000 Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote: > From: Wedson Almeida Filho <wedsonaf@xxxxxxxxx> > > Allow for the creation of a file descriptor in two steps: first, we > reserve a slot for it, then we commit or drop the reservation. The first > step may fail (e.g., the current process ran out of available slots), > but commit and drop never fail (and are mutually exclusive). > > This is needed by Rust Binder when fds are sent from one process to > another. It has to be a two-step process to properly handle the case > where multiple fds are sent: The operation must fail or succeed > atomically, which we achieve by first reserving the fds we need, and > only installing the files once we have reserved enough fds to send the > files. > > Fd reservations assume that the value of `current` does not change > between the call to get_unused_fd_flags and the call to fd_install (or > put_unused_fd). By not implementing the Send trait, this abstraction > ensures that the `FileDescriptorReservation` cannot be moved into a > different process. > > Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxx> > Co-developed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> > Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx> > Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx> > Reviewed-by: Trevor Gross <tmgross@xxxxxxxxx> > Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> Reviewed-by: Gary Guo <gary@xxxxxxxxxxx> > --- > rust/kernel/fs/file.rs | 75 +++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 74 insertions(+), 1 deletion(-)
