[PATCH v5 0/7] BorrowedPage, AsPageIter and VmallocPageIter

[PATCH v5 0/7] BorrowedPage, AsPageIter and VmallocPageIter

[Danilo Krummrich]

This patch series implements the BorrowedPage type, the AsPageIter trait and
VmallocPageIter type.

AsPageIter can be implemented by any type that owns pages to allow users to
borrow them through a generic interface.

For instance, this is useful to access and borrow the backing pages of
allocation primitives, such as Box and Vec, backing a scatterlist.

Hence, implement AsPageIter for VBox and VVec.

Additionally, implement Vmalloc::to_page() and ArrayLayout::size(), which are
dependencies of the above.

Changes in v5:
  - Avoid repetition in commit message of "rust: alloc: implement
    VmallocPageIter".
  - Change invariants of VmallocPageIter to:
    - `buf` is a valid and [`page::PAGE_SIZE`] aligned pointer into a
      [`Vmalloc`] allocation.
    - `size` is the number of bytes from `buf` until the end of the [`Vmalloc`]
      allocation `buf` points to.
  - Inline some methods of VmallocPageIter.

Changes in v4:
  - Rename IntoPageIter into AsPageIter.
  - Put lifetime on AsPageIter::Iter instead of AsPageIter itself.
  - Implement size_hint() for VmallocPageIter.
  - Use PhantomData<page::BorrowedPage<'a>> instead of PhantomData<&'a u8>.

Changes in v3:
  - Generalize the previous PageOwner impl of VBox and VVec in VmallocPageIter.
  - Correspondingly, replace PageOwner with IntoPageIter.

Changes in v2:
  - BorrowedPage
    - Add link to Ownable
    - Use borrow_page() in the example
  - Add PageOwner, Vmalloc::to_page(), ArrayLayout, VBox, VVec patches.

Danilo Krummrich (7):
  rust: page: implement BorrowedPage
  rust: alloc: vmalloc: implement Vmalloc::to_page()
  rust: alloc: implement VmallocPageIter
  rust: page: define trait AsPageIter
  rust: alloc: kbox: implement AsPageIter for VBox
  rust: alloc: layout: implement ArrayLayout::size()
  rust: alloc: kvec: implement AsPageIter for VVec

 rust/bindings/bindings_helper.h |   1 +
 rust/kernel/alloc/allocator.rs  | 152 ++++++++++++++++++++++++++++++++
 rust/kernel/alloc/kbox.rs       |  40 ++++++++-
 rust/kernel/alloc/kvec.rs       |  40 ++++++++-
 rust/kernel/alloc/layout.rs     |   5 ++
 rust/kernel/page.rs             |  87 +++++++++++++++++-
 6 files changed, 322 insertions(+), 3 deletions(-)


base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
-- 
2.50.1

[PATCH v5 1/7] rust: page: implement BorrowedPage

[Danilo Krummrich]

Currently, a Page always owns the underlying struct page.

However, sometimes a struct page may be owned by some other entity, e.g.
a vmalloc allocation.

Hence, introduce BorrowedPage to support such cases, until the Ownable
solution [1] lands.

This is required by the scatterlist abstractions.

Acked-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/rust-for-linux/ZnCzLIly3DRK2eab@boqun-archlinux/ [1]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/page.rs             | 75 ++++++++++++++++++++++++++++++++-
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 84d60635e8a9..0e140e07758b 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -57,6 +57,7 @@
 #include <linux/jiffies.h>
 #include <linux/jump_label.h>
 #include <linux/mdio.h>
+#include <linux/mm.h>
 #include <linux/miscdevice.h>
 #include <linux/of_device.h>
 #include <linux/pci.h>
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 7c1b17246ed5..631718a6ad7d 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -9,7 +9,12 @@
     error::Result,
     uaccess::UserSliceReader,
 };
-use core::ptr::{self, NonNull};
+use core::{
+    marker::PhantomData,
+    mem::ManuallyDrop,
+    ops::Deref,
+    ptr::{self, NonNull},
+};
 
 /// A bitwise shift for the page size.
 pub const PAGE_SHIFT: usize = bindings::PAGE_SHIFT as usize;
@@ -30,6 +35,74 @@ pub const fn page_align(addr: usize) -> usize {
     (addr + (PAGE_SIZE - 1)) & PAGE_MASK
 }
 
+/// Representation of a non-owning reference to a [`Page`].
+///
+/// This type provides a borrowed version of a [`Page`] that is owned by some other entity, e.g. a
+/// [`Vmalloc`] allocation such as [`VBox`].
+///
+/// # Example
+///
+/// ```
+/// # use kernel::{bindings, prelude::*};
+/// use kernel::page::{BorrowedPage, Page, PAGE_SIZE};
+/// # use core::{mem::MaybeUninit, ptr, ptr::NonNull };
+///
+/// fn borrow_page<'a>(vbox: &'a mut VBox<MaybeUninit<[u8; PAGE_SIZE]>>) -> BorrowedPage<'a> {
+///     let ptr = ptr::from_ref(&**vbox);
+///
+///     // SAFETY: `ptr` is a valid pointer to `Vmalloc` memory.
+///     let page = unsafe { bindings::vmalloc_to_page(ptr.cast()) };
+///
+///     // SAFETY: `vmalloc_to_page` returns a valid pointer to a `struct page` for a valid
+///     // pointer to `Vmalloc` memory.
+///     let page = unsafe { NonNull::new_unchecked(page) };
+///
+///     // SAFETY:
+///     // - `self.0` is a valid pointer to a `struct page`.
+///     // - `self.0` is valid for the entire lifetime of `self`.
+///     unsafe { BorrowedPage::from_raw(page) }
+/// }
+///
+/// let mut vbox = VBox::<[u8; PAGE_SIZE]>::new_uninit(GFP_KERNEL)?;
+/// let page = borrow_page(&mut vbox);
+///
+/// // SAFETY: There is no concurrent read or write to this page.
+/// unsafe { page.fill_zero_raw(0, PAGE_SIZE)? };
+/// # Ok::<(), Error>(())
+/// ```
+///
+/// # Invariants
+///
+/// The borrowed underlying pointer to a `struct page` is valid for the entire lifetime `'a`.
+///
+/// [`VBox`]: kernel::alloc::VBox
+/// [`Vmalloc`]: kernel::alloc::allocator::Vmalloc
+pub struct BorrowedPage<'a>(ManuallyDrop<Page>, PhantomData<&'a Page>);
+
+impl<'a> BorrowedPage<'a> {
+    /// Constructs a [`BorrowedPage`] from a raw pointer to a `struct page`.
+    ///
+    /// # Safety
+    ///
+    /// - `ptr` must point to a valid `bindings::page`.
+    /// - `ptr` must remain valid for the entire lifetime `'a`.
+    pub unsafe fn from_raw(ptr: NonNull<bindings::page>) -> Self {
+        let page = Page { page: ptr };
+
+        // INVARIANT: The safety requirements guarantee that `ptr` is valid for the entire lifetime
+        // `'a`.
+        Self(ManuallyDrop::new(page), PhantomData)
+    }
+}
+
+impl<'a> Deref for BorrowedPage<'a> {
+    type Target = Page;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
 /// A pointer to a page that owns the page allocation.
 ///
 /// # Invariants
-- 
2.50.1

[PATCH v5 2/7] rust: alloc: vmalloc: implement Vmalloc::to_page()

[Danilo Krummrich]

Implement an abstraction of vmalloc_to_page() for subsequent use in the
AsPageIter implementation of VBox and VVec.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/alloc/allocator.rs | 49 ++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index aa2dfa9dca4c..2315f5063011 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -15,6 +15,7 @@
 
 use crate::alloc::{AllocError, Allocator};
 use crate::bindings;
+use crate::page;
 use crate::pr_warn;
 
 /// The contiguous kernel allocator.
@@ -140,6 +141,54 @@ unsafe fn realloc(
     }
 }
 
+impl Vmalloc {
+    /// Convert a pointer to a [`Vmalloc`] allocation to a [`page::BorrowedPage`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use core::ptr::{NonNull, from_mut};
+    /// # use kernel::{page, prelude::*};
+    /// use kernel::alloc::allocator::Vmalloc;
+    ///
+    /// let mut vbox = VBox::<[u8; page::PAGE_SIZE]>::new_uninit(GFP_KERNEL)?;
+    ///
+    /// {
+    ///     // SAFETY: By the type invariant of `Box` the inner pointer of `vbox` is non-null.
+    ///     let ptr = unsafe { NonNull::new_unchecked(from_mut(&mut *vbox)) };
+    ///
+    ///     // SAFETY:
+    ///     // `ptr` is a valid pointer to a `Vmalloc` allocation.
+    ///     // `ptr` is valid for the entire lifetime of `page`.
+    ///     let page = unsafe { Vmalloc::to_page(ptr.cast()) };
+    ///
+    ///     // SAFETY: There is no concurrent read or write to the same page.
+    ///     unsafe { page.fill_zero_raw(0, page::PAGE_SIZE)? };
+    /// }
+    /// # Ok::<(), Error>(())
+    /// ```
+    ///
+    /// # Safety
+    ///
+    /// - `ptr` must be a valid pointer to a [`Vmalloc`] allocation.
+    /// - `ptr` must remain valid for the entire duration of `'a`.
+    pub unsafe fn to_page<'a>(ptr: NonNull<u8>) -> page::BorrowedPage<'a> {
+        // SAFETY: `ptr` is a valid pointer to `Vmalloc` memory.
+        let page = unsafe { bindings::vmalloc_to_page(ptr.as_ptr().cast()) };
+
+        // SAFETY: `vmalloc_to_page` returns a valid pointer to a `struct page` for a valid pointer
+        // to `Vmalloc` memory.
+        let page = unsafe { NonNull::new_unchecked(page) };
+
+        // SAFETY:
+        // - `page` is a valid pointer to a `struct page`, given that by the safety requirements of
+        //   this function `ptr` is a valid pointer to a `Vmalloc` allocation.
+        // - By the safety requirements of this function `ptr` is valid for the entire lifetime of
+        //   `'a`.
+        unsafe { page::BorrowedPage::from_raw(page) }
+    }
+}
+
 // SAFETY: `realloc` delegates to `ReallocFunc::call`, which guarantees that
 // - memory remains valid until it is explicitly freed,
 // - passing a pointer to a valid memory allocation is OK,
-- 
2.50.1

[PATCH v5 3/7] rust: alloc: implement VmallocPageIter

[Danilo Krummrich]

Introduce the VmallocPageIter type; an instance of VmallocPageIter may
be exposed by owners of vmalloc allocations to provide borrowed access
to its backing pages.

For instance, this is useful to access and borrow the backing pages of
allocation primitives, such as Box and Vec, backing a scatterlist.

Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/alloc/allocator.rs | 103 +++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 2315f5063011..103be3e68eac 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -10,6 +10,7 @@
 
 use super::Flags;
 use core::alloc::Layout;
+use core::marker::PhantomData;
 use core::ptr;
 use core::ptr::NonNull;
 
@@ -236,3 +237,105 @@ unsafe fn realloc(
         unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags) }
     }
 }
+
+/// An [`Iterator`] of [`page::BorrowedPage`] items owned by a [`Vmalloc`] allocation.
+///
+/// # Guarantees
+///
+/// The pages iterated by the [`Iterator`] appear in the order as they are mapped in the CPU's
+/// virtual address space ascendingly.
+///
+/// # Invariants
+///
+/// - `buf` is a valid and [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
+/// - `size` is the number of bytes from `buf` until the end of the [`Vmalloc`] allocation `buf`
+///   points to.
+pub struct VmallocPageIter<'a> {
+    /// The base address of the [`Vmalloc`] buffer.
+    buf: NonNull<u8>,
+    /// The size of the buffer pointed to by `buf` in bytes.
+    size: usize,
+    /// The current page index of the [`Iterator`].
+    index: usize,
+    _p: PhantomData<page::BorrowedPage<'a>>,
+}
+
+impl<'a> Iterator for VmallocPageIter<'a> {
+    type Item = page::BorrowedPage<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let offset = self.index.checked_mul(page::PAGE_SIZE)?;
+
+        // Even though `self.size()` may be smaller than `Self::page_count() * page::PAGE_SIZE`, it
+        // is always a number between `(Self::page_count() - 1) * page::PAGE_SIZE` and
+        // `Self::page_count() * page::PAGE_SIZE`, hence the check below is sufficient.
+        if offset < self.size() {
+            self.index += 1;
+        } else {
+            return None;
+        }
+
+        // TODO: Use `NonNull::add()` instead, once the minimum supported compiler version is
+        // bumped to 1.80 or later.
+        //
+        // SAFETY: `offset` is in the interval `[0, (self.page_count() - 1) * page::PAGE_SIZE]`,
+        // hence the resulting pointer is guaranteed to be within the same allocation.
+        let ptr = unsafe { self.buf.as_ptr().add(offset) };
+
+        // SAFETY: `ptr` is guaranteed to be non-null given that it is derived from `self.buf`.
+        let ptr = unsafe { NonNull::new_unchecked(ptr) };
+
+        // SAFETY:
+        // - `ptr` is a valid pointer to a `Vmalloc` allocation.
+        // - `ptr` is valid for the duration of `'a`.
+        Some(unsafe { Vmalloc::to_page(ptr) })
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let remaining = self.page_count().saturating_sub(self.index);
+
+        (remaining, Some(remaining))
+    }
+}
+
+impl<'a> VmallocPageIter<'a> {
+    /// Creates a new [`VmallocPageIter`] instance.
+    ///
+    /// # Safety
+    ///
+    /// - `buf` must be a [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
+    /// - `buf` must be valid for at least the lifetime of `'a`.
+    /// - `size` must be the number of bytes from `buf` until the end of the [`Vmalloc`] allocation
+    ///   `buf` points to.
+    pub unsafe fn new(buf: NonNull<u8>, size: usize) -> Self {
+        // INVARIANT: By the safety requirements, `buf` is a valid and `page::PAGE_SIZE` aligned
+        // pointer into a [`Vmalloc`] allocation.
+        Self {
+            buf,
+            size,
+            index: 0,
+            _p: PhantomData,
+        }
+    }
+
+    /// Returns the base address of the backing [`Vmalloc`] allocation.
+    #[inline]
+    pub fn base_address(&self) -> NonNull<u8> {
+        self.buf
+    }
+
+    /// Returns the size of the backing [`Vmalloc`] allocation in bytes.
+    ///
+    /// Note that this is the size the [`Vmalloc`] allocation has been allocated with. Hence, this
+    /// number may be smaller than `[`Self::page_count`] * [`page::PAGE_SIZE`]`.
+    #[inline]
+    pub fn size(&self) -> usize {
+        self.size
+    }
+
+    /// Returns the number of pages owned by the backing [`Vmalloc`] allocation.
+    #[inline]
+    pub fn page_count(&self) -> usize {
+        self.size().div_ceil(page::PAGE_SIZE)
+    }
+}
-- 
2.50.1

[PATCH v5 4/7] rust: page: define trait AsPageIter

[Danilo Krummrich]

The AsPageIter trait provides a common interface for types that
provide a page iterator, such as VmallocPageIter.

Subsequent patches will leverage this to let VBox and VVec provide a
VmallocPageIter though this trait.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/page.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 631718a6ad7d..75ef096075cb 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -103,6 +103,18 @@ fn deref(&self) -> &Self::Target {
     }
 }
 
+/// Trait to be implemented by types which provide an [`Iterator`] implementation of
+/// [`BorrowedPage`] items, such as [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
+pub trait AsPageIter {
+    /// The [`Iterator`] type, e.g. [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
+    type Iter<'a>: Iterator<Item = BorrowedPage<'a>>
+    where
+        Self: 'a;
+
+    /// Returns an [`Iterator`] of [`BorrowedPage`] items over all pages owned by `self`.
+    fn page_iter(&mut self) -> Self::Iter<'_>;
+}
+
 /// A pointer to a page that owns the page allocation.
 ///
 /// # Invariants
-- 
2.50.1

[PATCH v5 5/7] rust: alloc: kbox: implement AsPageIter for VBox

[Danilo Krummrich]

Implement AsPageIter for VBox; this allows to iterate and borrow the
backing pages of a VBox. This, for instance, is useful in combination
with VBox backing a scatterlist.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/alloc/kbox.rs | 40 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
index 856d05aa60f1..b69ff4a1d748 100644
--- a/rust/kernel/alloc/kbox.rs
+++ b/rust/kernel/alloc/kbox.rs
@@ -3,7 +3,7 @@
 //! Implementation of [`Box`].
 
 #[allow(unused_imports)] // Used in doc comments.
-use super::allocator::{KVmalloc, Kmalloc, Vmalloc};
+use super::allocator::{KVmalloc, Kmalloc, Vmalloc, VmallocPageIter};
 use super::{AllocError, Allocator, Flags};
 use core::alloc::Layout;
 use core::borrow::{Borrow, BorrowMut};
@@ -18,6 +18,7 @@
 
 use crate::ffi::c_void;
 use crate::init::InPlaceInit;
+use crate::page::AsPageIter;
 use crate::types::ForeignOwnable;
 use pin_init::{InPlaceWrite, Init, PinInit, ZeroableOption};
 
@@ -598,3 +599,40 @@ fn drop(&mut self) {
         unsafe { A::free(self.0.cast(), layout) };
     }
 }
+
+/// # Examples
+///
+/// ```
+/// # use kernel::prelude::*;
+/// use kernel::alloc::allocator::VmallocPageIter;
+/// use kernel::page::{AsPageIter, PAGE_SIZE};
+///
+/// let mut vbox = VBox::new((), GFP_KERNEL)?;
+///
+/// assert!(vbox.page_iter().next().is_none());
+///
+/// let mut vbox = VBox::<[u8; PAGE_SIZE]>::new_uninit(GFP_KERNEL)?;
+///
+/// let page = vbox.page_iter().next().expect("At least one page should be available.\n");
+///
+/// // SAFETY: There is no concurrent read or write to the same page.
+/// unsafe { page.fill_zero_raw(0, PAGE_SIZE)? };
+/// # Ok::<(), Error>(())
+/// ```
+impl<T> AsPageIter for VBox<T> {
+    type Iter<'a>
+        = VmallocPageIter<'a>
+    where
+        T: 'a;
+
+    fn page_iter(&mut self) -> Self::Iter<'_> {
+        let ptr = self.0.cast();
+        let size = core::mem::size_of::<T>();
+
+        // SAFETY:
+        // - `ptr` is a valid pointer to the beginning of a `Vmalloc` allocation.
+        // - `ptr` is guaranteed to be valid for the lifetime of `'a`.
+        // - `size` is the size of the `Vmalloc` allocation `ptr` points to.
+        unsafe { VmallocPageIter::new(ptr, size) }
+    }
+}
-- 
2.50.1

[PATCH v5 6/7] rust: alloc: layout: implement ArrayLayout::size()

[Danilo Krummrich]

Provide a convenience method for ArrayLayout to calculate the size of
the ArrayLayout in bytes.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/alloc/layout.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/rust/kernel/alloc/layout.rs b/rust/kernel/alloc/layout.rs
index 93ed514f7cc7..666accb7859c 100644
--- a/rust/kernel/alloc/layout.rs
+++ b/rust/kernel/alloc/layout.rs
@@ -98,6 +98,11 @@ pub const fn len(&self) -> usize {
     pub const fn is_empty(&self) -> bool {
         self.len == 0
     }
+
+    /// Returns the size of the [`ArrayLayout`] in bytes.
+    pub const fn size(&self) -> usize {
+        self.len() * core::mem::size_of::<T>()
+    }
 }
 
 impl<T> From<ArrayLayout<T>> for Layout {
-- 
2.50.1

[PATCH v5 7/7] rust: alloc: kvec: implement AsPageIter for VVec

[Danilo Krummrich]

Implement AsPageIter for VVec; this allows to iterate and borrow the
backing pages of a VVec. This, for instance, is useful in combination
with VVec backing a scatterlist.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/alloc/kvec.rs | 40 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index 3c72e0bdddb8..ac438e70a1ed 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -3,10 +3,11 @@
 //! Implementation of [`Vec`].
 
 use super::{
-    allocator::{KVmalloc, Kmalloc, Vmalloc},
+    allocator::{KVmalloc, Kmalloc, Vmalloc, VmallocPageIter},
     layout::ArrayLayout,
     AllocError, Allocator, Box, Flags,
 };
+use crate::page::AsPageIter;
 use core::{
     borrow::{Borrow, BorrowMut},
     fmt,
@@ -1017,6 +1018,43 @@ fn into_iter(self) -> Self::IntoIter {
     }
 }
 
+/// # Examples
+///
+/// ```
+/// # use kernel::prelude::*;
+/// use kernel::alloc::allocator::VmallocPageIter;
+/// use kernel::page::{AsPageIter, PAGE_SIZE};
+///
+/// let mut vec = VVec::<u8>::new();
+///
+/// assert!(vec.page_iter().next().is_none());
+///
+/// vec.reserve(PAGE_SIZE, GFP_KERNEL)?;
+///
+/// let page = vec.page_iter().next().expect("At least one page should be available.\n");
+///
+/// // SAFETY: There is no concurrent read or write to the same page.
+/// unsafe { page.fill_zero_raw(0, PAGE_SIZE)? };
+/// # Ok::<(), Error>(())
+/// ```
+impl<T> AsPageIter for VVec<T> {
+    type Iter<'a>
+        = VmallocPageIter<'a>
+    where
+        T: 'a;
+
+    fn page_iter(&mut self) -> Self::Iter<'_> {
+        let ptr = self.ptr.cast();
+        let size = self.layout.size();
+
+        // SAFETY:
+        // - `ptr` is a valid pointer to the beginning of a `Vmalloc` allocation.
+        // - `ptr` is guaranteed to be valid for the lifetime of `'a`.
+        // - `size` is the size of the `Vmalloc` allocation `ptr` points to.
+        unsafe { VmallocPageIter::new(ptr, size) }
+    }
+}
+
 /// An [`Iterator`] implementation for [`Vec`] that moves elements out of a vector.
 ///
 /// This structure is created by the [`Vec::into_iter`] method on [`Vec`] (provided by the
-- 
2.50.1

Re: [PATCH v5 0/7] BorrowedPage, AsPageIter and VmallocPageIter

[Danilo Krummrich]

On Wed Aug 20, 2025 at 4:53 PM CEST, Danilo Krummrich wrote:
> Danilo Krummrich (7):

Applied to drm-rust-next, thanks!

>   rust: page: implement BorrowedPage
>   rust: alloc: vmalloc: implement Vmalloc::to_page()
>   rust: alloc: implement VmallocPageIter

    [ Drop VmallocPageIter::base_address(), move to allocator/iter.rs and
      stub VmallocPageIter for allocator_test.rs. - Danilo ]

>   rust: page: define trait AsPageIter
>   rust: alloc: kbox: implement AsPageIter for VBox
>   rust: alloc: layout: implement ArrayLayout::size()
>   rust: alloc: kvec: implement AsPageIter for VVec