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Date: Sat, 10 Jun 2023 18:49:09 +0800
From: "Qingsong Chen" <changxian.cqs@...group.com>
To: linux-kernel@...r.kernel.org
Cc: "田洪亮" <tate.thl@...group.com>,
"Qingsong Chen" <changxian.cqs@...group.com>,
"Miguel Ojeda" <ojeda@...nel.org>,
"Alex Gaynor" <alex.gaynor@...il.com>,
"Wedson Almeida Filho" <wedsonaf@...il.com>,
"Boqun Feng" <boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
"Björn Roy Baron" <bjorn3_gh@...tonmail.com>,
"Benno Lossin" <benno.lossin@...ton.me>,
<rust-for-linux@...r.kernel.org>
Subject: [PATCH v3 3/3] rust: kernel: add SgTable abstraction
SgTable is similar to `struct sg_table`, consisted of
scatterlist entries, and could be chained with each other.
Signed-off-by: Qingsong Chen <changxian.cqs@...group.com>
---
rust/kernel/scatterlist.rs | 198 +++++++++++++++++++++++++++++++++++++
1 file changed, 198 insertions(+)
diff --git a/rust/kernel/scatterlist.rs b/rust/kernel/scatterlist.rs
index 41e268b93c9e..870904d53e81 100644
--- a/rust/kernel/scatterlist.rs
+++ b/rust/kernel/scatterlist.rs
@@ -349,3 +349,201 @@ impl<'a> Iterator for IterMut<'a> {
}
}
}
+
+/// A [`ScatterList`] table of fixed `N` entries.
+///
+/// According to the design of kernel's `struct sg_table`, the `page_link`
+/// field of one `scatterlist` may contain a pointer to another. That is,
+/// there could exist external pointers to it, making it necessary to pin
+/// this struct.
+///
+/// If the table is chainable, the last entry will be reserved for chaining.
+/// The recommended way to create such instances is with the [`pin_init`].
+///
+/// # Examples
+///
+/// The following are some use cases of [`SgTable<N>`].
+///
+/// ```rust
+/// use core::pin::pin;;
+/// # use kernel::error::Result;
+/// # use kernel::scatterlist::{ScatterList, SgTable};
+///
+/// // Prepare memory buffers.
+/// let buf0: Pin<&mut [u8]> = pin!([0u8; 512]);
+/// let buf1: Pin<&mut [u8]> = pin!([1u8; 512]);
+/// let mut entries: Vec<Pin<&mut [u8]>> = Vec::<Pin<&mut [u8]>>::new();
+/// entries.try_push(buf0)?;
+/// entries.try_push(buf1)?;
+///
+/// // Allocate an instance on stack.
+/// kernel::stack_try_pin_init!(let foo =? SgTable::new(entries.as_slice(), false));
+/// let mut foo: Pin<&mut SgTable<'_, 2>> = foo;
+/// assert_eq!(foo.count(), 2);
+///
+/// // Allocate a chainable instance by Box::pin_init.
+/// let mut bar: Pin<Box<SgTable<'_, 3>>> = Box::pin_init(SgTable::new(entries.as_slice(), true))?;
+/// assert_eq!(bar.count(), 2);
+///
+/// // Chain two `SgTable` together.
+/// bar.chain_sgt(foo.as_mut())?;
+/// assert_eq!(bar.count(), 4);
+///
+/// // Get an immutable reference to the entry in the table.
+/// let sgl1: Pin<&ScatterList<'_>> = bar.get(1).ok_or(EINVAL)?;
+/// assert_eq!(sgl1.count(), 3);
+/// assert_eq!(sgl1.get_buf(), [1u8; 512]);
+///
+/// // Get a mutable reference to the entry in the table.
+/// let sgl2: Pin<&mut ScatterList<'_>> = bar.get_mut(2).ok_or(EINVAL)?;
+/// assert_eq!(sgl2.count(), 2);
+/// assert_eq!(sgl2.get_buf(), [0u8; 512]);
+///
+/// // Try to get a non-exist entry from the table.
+/// let sgl4 = bar.get(4);
+/// assert_eq!(sgl4.is_none(), true);
+///
+/// // Split the first table from chained scatterlist.
+/// bar.split()?;
+/// assert_eq!(bar.count(), 2);
+/// ```
+#[pin_data]
+pub struct SgTable<'a, const N: usize> {
+ #[pin]
+ entries: [ScatterList<'a>; N],
+}
+
+impl<'a, const N: usize> SgTable<'a, N> {
+ /// Construct a new initializer.
+ ///
+ /// # Errors
+ ///
+ /// The length of `entries` should exactly be the available size of [`SgTable<N>`],
+ /// or else an error is returned.
+ ///
+ /// If the table is `chainable`, the available size is `N - 1`, because one entry
+ /// should be reserved for chaining.
+ pub fn new(
+ entries: &'a [Pin<&mut [u8]>],
+ chainable: bool,
+ ) -> impl PinInit<SgTable<'a, N>, Error> {
+ build_assert!(N > 0);
+ // SAFETY: `slot` is valid while the closure is called, the `entries` are
+ // pinned and valid.
+ unsafe {
+ init::pin_init_from_closure(move |slot: *mut Self| {
+ let mut nr_entry = N;
+ if chainable {
+ nr_entry -= 1;
+ }
+ if nr_entry == 0 || entries.len() != nr_entry {
+ return Err(EINVAL);
+ }
+
+ for i in 0..nr_entry {
+ // `slot` contains uninit memory, avoid creating a reference.
+ let opaque = addr_of!((*slot).entries[i].opaque);
+ let sgl = Opaque::raw_get(opaque);
+
+ bindings::sg_set_buf(sgl, entries[i].as_ptr() as _, entries[i].len() as _);
+ if i + 1 == nr_entry {
+ (*sgl).page_link |= bindings::SG_END as u64;
+ (*sgl).page_link &= !(bindings::SG_CHAIN as u64);
+ }
+ }
+ Ok(())
+ })
+ }
+ }
+
+ /// Chain two [`SgTable`] together.
+ ///
+ /// Transfer the last entry of this table as a chainable pointer to the
+ /// first entry of `sgt` SgTable.
+ ///
+ /// # Errors
+ ///
+ /// Return an error if this table is not chainable or has been chained.
+ pub fn chain_sgt<const M: usize>(&mut self, sgt: Pin<&mut SgTable<'_, M>>) -> Result {
+ if self.count() != N - 1 {
+ return Err(EINVAL);
+ }
+ self.entries[N - 2].unmark_end();
+
+ // SAFETY: `sgt.entries` are initialized by the `new` constructor,
+ // so it's valid.
+ let next = unsafe { ScatterList::as_mut(sgt.entries[0].opaque.get()).unwrap() };
+ self.entries[N - 1].chain_sgl(next);
+ Ok(())
+ }
+
+ /// Chain [`SgTable`] and [`ScatterList`] together.
+ ///
+ /// Transfer the last entry of this table as a chainable pointer to `sgl`
+ /// scatterlist.
+ ///
+ /// # Errors
+ ///
+ /// Return an error if this table is not chainable or has been chained.
+ pub fn chain_sgl(&mut self, sgl: Pin<&mut ScatterList<'_>>) -> Result {
+ if self.count() != N - 1 {
+ return Err(EINVAL);
+ }
+ self.entries[N - 2].unmark_end();
+ self.entries[N - 1].chain_sgl(sgl);
+ Ok(())
+ }
+
+ /// Split the first table from chained scatterlist.
+ ///
+ /// # Errors
+ ///
+ /// Return an error if this table is not chainable or has not been chained.
+ pub fn split(&mut self) -> Result {
+ if !self.entries[N - 1].is_chain() {
+ return Err(EINVAL);
+ }
+ self.entries[N - 2].mark_end();
+ Ok(())
+ }
+
+ /// Return the total count of normal entries in the table.
+ ///
+ /// It allows to know how many entries are in the table, taking into account
+ /// chaining as well.
+ pub fn count(&self) -> usize {
+ // SAFETY: `self.entries` are initialized by the `new` constructor,
+ // so it's valid.
+ unsafe { bindings::sg_nents(self.entries[0].opaque.get()) as _ }
+ }
+
+ /// Get an immutable reference to `n`th entry in the table.
+ ///
+ /// Like most indexing operations, the count starts from zero. Return None
+ /// if `n` is greater than or equal to the total count of entries.
+ pub fn get(&self, n: usize) -> Option<Pin<&ScatterList<'_>>> {
+ self.iter().nth(n)
+ }
+
+ /// Get a mutable reference to `n`th entry in the table.
+ ///
+ /// Like most indexing operations, the count starts from zero. Return None
+ /// if `n` is greater than or equal to the number of total entries.
+ pub fn get_mut(&mut self, n: usize) -> Option<Pin<&mut ScatterList<'_>>> {
+ self.iter_mut().nth(n)
+ }
+
+ /// Get an iterator for immutable entries.
+ pub fn iter(&self) -> Iter<'_> {
+ // SAFETY: `self.entries` are initialized by the `new` constructor,
+ // so it's valid.
+ unsafe { Iter(ScatterList::as_ref(self.entries[0].opaque.get())) }
+ }
+
+ /// Get an iterator for mutable entries.
+ pub fn iter_mut(&mut self) -> IterMut<'_> {
+ // SAFETY: `self.entries` are initialized by the `new` constructor,
+ // so it's valid.
+ unsafe { IterMut(ScatterList::as_mut(self.entries[0].opaque.get())) }
+ }
+}
--
2.40.1
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