Re: [RFC PATCH v2 10/10] rust: puzzlefs: add oci_root_dir and image_manifest filesystem parameters

[Trevor Gross <tmgross@umich.edu>]

On Wed, Jul 26, 2023 at 12:55 PM Ariel Miculas <amiculas@cisco.com> wrote:
>
> These parameters are passed when mounting puzzlefs using '-o' option of
> mount:
> -o oci_root_dir="/path/to/oci/dir"
> -o image_manifest="root_hash_of_image_manifest"
>
> For a particular manifest in the manifests array in index.json (located
> in the oci_root_dir), the root hash of the image manifest is found in
> the digest field.
>
> It would be nicer if we could pass the tag, but we don't support json
> deserialization.
>
> Example of mount:
> mount -t puzzlefs -o oci_root_dir="/home/puzzlefs_oci" -o \
> image_manifest="2d6602d678140540dc7e96de652a76a8b16e8aca190bae141297bcffdcae901b" \
> none /mnt
>
> Signed-off-by: Ariel Miculas <amiculas@cisco.com>
> ---
>  samples/rust/puzzlefs.rs | 63 ++++++++++++++++++++++++++--------------
>  1 file changed, 41 insertions(+), 22 deletions(-)
>
> diff --git a/samples/rust/puzzlefs.rs b/samples/rust/puzzlefs.rs
> index dad7ecc76eca..4e9a8aedf0c1 100644
> --- a/samples/rust/puzzlefs.rs
> +++ b/samples/rust/puzzlefs.rs
> @@ -7,6 +7,7 @@
>  use kernel::{
>      c_str, file, fs,
>      io_buffer::IoBufferWriter,
> +    str::CString,
>      sync::{Arc, ArcBorrow},
>  };
>
> @@ -31,27 +32,29 @@ struct PuzzlefsInfo {
>      puzzlefs: Arc<PuzzleFS>,
>  }
>
> +#[derive(Default)]
> +struct PuzzleFsParams {
> +    oci_root_dir: Option<CString>,
> +    image_manifest: Option<CString>,
> +}
> +
>  #[vtable]
>  impl fs::Context<Self> for PuzzleFsModule {
> -    type Data = ();
> -
> -    kernel::define_fs_params! {(),
> -        {flag, "flag", |_, v| { pr_info!("flag passed-in: {v}\n"); Ok(()) } },
> -        {flag_no, "flagno", |_, v| { pr_info!("flagno passed-in: {v}\n"); Ok(()) } },
> -        {bool, "bool", |_, v| { pr_info!("bool passed-in: {v}\n"); Ok(()) } },
> -        {u32, "u32", |_, v| { pr_info!("u32 passed-in: {v}\n"); Ok(()) } },
> -        {u32oct, "u32oct", |_, v| { pr_info!("u32oct passed-in: {v}\n"); Ok(()) } },
> -        {u32hex, "u32hex", |_, v| { pr_info!("u32hex passed-in: {v}\n"); Ok(()) } },
> -        {s32, "s32", |_, v| { pr_info!("s32 passed-in: {v}\n"); Ok(()) } },
> -        {u64, "u64", |_, v| { pr_info!("u64 passed-in: {v}\n"); Ok(()) } },
> -        {string, "string", |_, v| { pr_info!("string passed-in: {v}\n"); Ok(()) } },
> -        {enum, "enum", [("first", 10), ("second", 20)], |_, v| {
> -            pr_info!("enum passed-in: {v}\n"); Ok(()) }
> -        },
> +    type Data = Box<PuzzleFsParams>;
> +
> +    kernel::define_fs_params! {Box<PuzzleFsParams>,
> +        {string, "oci_root_dir", |s, v| {
> +                                      s.oci_root_dir = Some(CString::try_from_fmt(format_args!("{v}"))?);
> +                                      Ok(())
> +                                  }},
> +        {string, "image_manifest", |s, v| {
> +                                      s.image_manifest = Some(CString::try_from_fmt(format_args!("{v}"))?);
> +                                      Ok(())
> +                                  }},
>      }
>
> -    fn try_new() -> Result {
> -        Ok(())
> +    fn try_new() -> Result<Self::Data> {
> +        Ok(Box::try_new(PuzzleFsParams::default())?)
>      }
>  }
>
> @@ -136,11 +139,27 @@ impl fs::Type for PuzzleFsModule {
>      const FLAGS: i32 = fs::flags::USERNS_MOUNT;
>      const DCACHE_BASED: bool = true;
>
> -    fn fill_super(_data: (), sb: fs::NewSuperBlock<'_, Self>) -> Result<&fs::SuperBlock<Self>> {
> -        let puzzlefs = PuzzleFS::open(
> -            c_str!("/home/puzzlefs_oci"),
> -            c_str!("2d6602d678140540dc7e96de652a76a8b16e8aca190bae141297bcffdcae901b"),
> -        );
> +    fn fill_super(
> +        data: Box<PuzzleFsParams>,
> +        sb: fs::NewSuperBlock<'_, Self>,
> +    ) -> Result<&fs::SuperBlock<Self>> {
> +        let oci_root_dir = match data.oci_root_dir {
> +            Some(val) => val,
> +            None => {
> +                pr_err!("missing oci_root_dir parameter!\n");
> +                return Err(ENOTSUPP);
> +            }
> +        };
> +
> +        let image_manifest = match data.image_manifest {
> +            Some(val) => val,
> +            None => {
> +                pr_err!("missing image_manifest parameter!\n");
> +                return Err(ENOTSUPP);
> +            }
> +        };
> +

The guard syntax (available since 1.65) can make these kinds of match statements
cleaner:

    let Some(oci_root_dir) = data.oci_root_dir else {
        pr_err!("missing oci_root_dir parameter!\n");
        return Err(ENOTSUPP);
    }

    let Some(image_manifest) ...

> +        let puzzlefs = PuzzleFS::open(&oci_root_dir, &image_manifest);
>
>          if let Err(ref e) = puzzlefs {
>              pr_info!("error opening puzzlefs {e}\n");
> --
> 2.41.0
>
>