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

[Wedson Almeida Filho]

On Wed, 26 Jul 2023 at 18:08, Trevor Gross <tmgross@xxxxxxxxx> wrote:
>
> On Wed, Jul 26, 2023 at 12:55 PM Ariel Miculas <amiculas@xxxxxxxxx> 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@xxxxxxxxx>
> > ---
> >  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:

This is unstable though.

We try to stay away from unstable features unless we really need them,
which I feel is not the case here.

>     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
> >
> >