| Message ID | 20241001150008.183102-10-dakr@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Generic `Allocator` support for Rust | expand |
On Tue, 1 Oct 2024 16:59:44 +0200 Danilo Krummrich <dakr@kernel.org> wrote: > Implement `Allocator` for `KVmalloc`, an `Allocator` that tries to > allocate memory wth `kmalloc` first and, on failure, falls back to > `vmalloc`. > > All memory allocations made with `KVmalloc` end up in > `kvrealloc_noprof()`; all frees in `kvfree()`. > > Reviewed-by: Alice Ryhl <aliceryhl@google.com> > Reviewed-by: Benno Lossin <benno.lossin@proton.me> > Signed-off-by: Danilo Krummrich <dakr@kernel.org> Reviewed-by: Gary Guo <gary@garyguo.net> > --- > rust/helpers/slab.c | 6 +++++ > rust/kernel/alloc/allocator.rs | 36 +++++++++++++++++++++++++++++ > rust/kernel/alloc/allocator_test.rs | 1 + > 3 files changed, 43 insertions(+) > > diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c > index f043e087f9d6..a842bfbddcba 100644 > --- a/rust/helpers/slab.c > +++ b/rust/helpers/slab.c > @@ -7,3 +7,9 @@ rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags) > { > return krealloc(objp, new_size, flags); > } > + > +void * __must_check __realloc_size(2) > +rust_helper_kvrealloc(const void *p, size_t size, gfp_t flags) > +{ > + return kvrealloc(p, size, flags); > +} > diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs > index f341e9ed5b7c..d0a8819c6741 100644 > --- a/rust/kernel/alloc/allocator.rs > +++ b/rust/kernel/alloc/allocator.rs > @@ -34,6 +34,15 @@ > /// For more details see [self]. > pub struct Vmalloc; > > +/// The kvmalloc kernel allocator. > +/// > +/// `KVmalloc` attempts to allocate memory with `Kmalloc` first, but falls back to `Vmalloc` upon > +/// failure. This allocator is typically used when the size for the requested allocation is not > +/// known and may exceed the capabilities of `Kmalloc`. > +/// > +/// For more details see [self]. > +pub struct KVmalloc; > + > /// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment. > fn aligned_size(new_layout: Layout) -> usize { > // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. > @@ -76,6 +85,9 @@ impl ReallocFunc { > // INVARIANT: `vrealloc` satisfies the type invariants. > const VREALLOC: Self = Self(bindings::vrealloc); > > + // INVARIANT: `kvrealloc` satisfies the type invariants. > + const KVREALLOC: Self = Self(bindings::kvrealloc); > + > /// # Safety > /// > /// This method has the same safety requirements as [`Allocator::realloc`]. > @@ -203,6 +215,30 @@ unsafe fn realloc( > } > } > > +// 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, > +// - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same. > +unsafe impl Allocator for KVmalloc { > + #[inline] > + unsafe fn realloc( > + ptr: Option<NonNull<u8>>, > + layout: Layout, > + old_layout: Layout, > + flags: Flags, > + ) -> Result<NonNull<[u8]>, AllocError> { > + // TODO: Support alignments larger than PAGE_SIZE. > + if layout.align() > bindings::PAGE_SIZE { > + pr_warn!("KVmalloc does not support alignments larger than PAGE_SIZE yet.\n"); > + return Err(AllocError); > + } > + > + // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously > + // allocated with this `Allocator`. > + unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags) } > + } > +} > + > #[global_allocator] > static ALLOCATOR: Kmalloc = Kmalloc; > > diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs > index e7bf2982f68f..1b2642c547ec 100644 > --- a/rust/kernel/alloc/allocator_test.rs > +++ b/rust/kernel/alloc/allocator_test.rs > @@ -8,6 +8,7 @@ > > pub struct Kmalloc; > pub type Vmalloc = Kmalloc; > +pub type KVmalloc = Kmalloc; > > unsafe impl Allocator for Kmalloc { > unsafe fn realloc(
diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c index f043e087f9d6..a842bfbddcba 100644 --- a/rust/helpers/slab.c +++ b/rust/helpers/slab.c @@ -7,3 +7,9 @@ rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags) { return krealloc(objp, new_size, flags); } + +void * __must_check __realloc_size(2) +rust_helper_kvrealloc(const void *p, size_t size, gfp_t flags) +{ + return kvrealloc(p, size, flags); +} diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs index f341e9ed5b7c..d0a8819c6741 100644 --- a/rust/kernel/alloc/allocator.rs +++ b/rust/kernel/alloc/allocator.rs @@ -34,6 +34,15 @@ /// For more details see [self]. pub struct Vmalloc; +/// The kvmalloc kernel allocator. +/// +/// `KVmalloc` attempts to allocate memory with `Kmalloc` first, but falls back to `Vmalloc` upon +/// failure. This allocator is typically used when the size for the requested allocation is not +/// known and may exceed the capabilities of `Kmalloc`. +/// +/// For more details see [self]. +pub struct KVmalloc; + /// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment. fn aligned_size(new_layout: Layout) -> usize { // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. @@ -76,6 +85,9 @@ impl ReallocFunc { // INVARIANT: `vrealloc` satisfies the type invariants. const VREALLOC: Self = Self(bindings::vrealloc); + // INVARIANT: `kvrealloc` satisfies the type invariants. + const KVREALLOC: Self = Self(bindings::kvrealloc); + /// # Safety /// /// This method has the same safety requirements as [`Allocator::realloc`]. @@ -203,6 +215,30 @@ unsafe fn realloc( } } +// 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, +// - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same. +unsafe impl Allocator for KVmalloc { + #[inline] + unsafe fn realloc( + ptr: Option<NonNull<u8>>, + layout: Layout, + old_layout: Layout, + flags: Flags, + ) -> Result<NonNull<[u8]>, AllocError> { + // TODO: Support alignments larger than PAGE_SIZE. + if layout.align() > bindings::PAGE_SIZE { + pr_warn!("KVmalloc does not support alignments larger than PAGE_SIZE yet.\n"); + return Err(AllocError); + } + + // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously + // allocated with this `Allocator`. + unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags) } + } +} + #[global_allocator] static ALLOCATOR: Kmalloc = Kmalloc; diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs index e7bf2982f68f..1b2642c547ec 100644 --- a/rust/kernel/alloc/allocator_test.rs +++ b/rust/kernel/alloc/allocator_test.rs @@ -8,6 +8,7 @@ pub struct Kmalloc; pub type Vmalloc = Kmalloc; +pub type KVmalloc = Kmalloc; unsafe impl Allocator for Kmalloc { unsafe fn realloc(