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ab44079e28
Make it possible to allocate memory that doesn't need to mapped into the kernel's address space. This flag is useful together with Page::alloc_page [1]. Rust Binder needs this for the memory that holds incoming transactions for each process. Each process will have a few megabytes of memory allocated with this flag, which is mapped into the process using vm_insert_page. When the kernel copies data for an incoming transaction into a process's memory region, it will use kmap_local_page to temporarily map pages that are being modified. There is no need for them to take up address space in the kernel when the kernel is not writing an incoming transaction into the page. Link: https://lore.kernel.org/all/20240528-alice-mm-v7-4-78222c31b8f4@google.com/ [1] Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240607-highmem-v1-1-d18c5ca4072f@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
82 lines
2.5 KiB
Rust
82 lines
2.5 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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//! Extensions to the [`alloc`] crate.
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#[cfg(not(test))]
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#[cfg(not(testlib))]
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mod allocator;
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pub mod box_ext;
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pub mod vec_ext;
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/// Indicates an allocation error.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub struct AllocError;
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/// Flags to be used when allocating memory.
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///
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/// They can be combined with the operators `|`, `&`, and `!`.
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///
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/// Values can be used from the [`flags`] module.
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#[derive(Clone, Copy)]
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pub struct Flags(u32);
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impl core::ops::BitOr for Flags {
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type Output = Self;
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fn bitor(self, rhs: Self) -> Self::Output {
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Self(self.0 | rhs.0)
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}
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}
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impl core::ops::BitAnd for Flags {
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type Output = Self;
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fn bitand(self, rhs: Self) -> Self::Output {
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Self(self.0 & rhs.0)
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}
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}
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impl core::ops::Not for Flags {
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type Output = Self;
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fn not(self) -> Self::Output {
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Self(!self.0)
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}
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}
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/// Allocation flags.
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///
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/// These are meant to be used in functions that can allocate memory.
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pub mod flags {
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use super::Flags;
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/// Zeroes out the allocated memory.
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///
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/// This is normally or'd with other flags.
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pub const __GFP_ZERO: Flags = Flags(bindings::__GFP_ZERO);
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/// Allow the allocation to be in high memory.
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///
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/// Allocations in high memory may not be mapped into the kernel's address space, so this can't
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/// be used with `kmalloc` and other similar methods.
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///
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/// This is normally or'd with other flags.
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pub const __GFP_HIGHMEM: Flags = Flags(bindings::__GFP_HIGHMEM);
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/// Users can not sleep and need the allocation to succeed.
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///
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/// A lower watermark is applied to allow access to "atomic reserves". The current
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/// implementation doesn't support NMI and few other strict non-preemptive contexts (e.g.
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/// raw_spin_lock). The same applies to [`GFP_NOWAIT`].
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pub const GFP_ATOMIC: Flags = Flags(bindings::GFP_ATOMIC);
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/// Typical for kernel-internal allocations. The caller requires ZONE_NORMAL or a lower zone
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/// for direct access but can direct reclaim.
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pub const GFP_KERNEL: Flags = Flags(bindings::GFP_KERNEL);
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/// The same as [`GFP_KERNEL`], except the allocation is accounted to kmemcg.
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pub const GFP_KERNEL_ACCOUNT: Flags = Flags(bindings::GFP_KERNEL_ACCOUNT);
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/// For kernel allocations that should not stall for direct reclaim, start physical IO or
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/// use any filesystem callback. It is very likely to fail to allocate memory, even for very
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/// small allocations.
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pub const GFP_NOWAIT: Flags = Flags(bindings::GFP_NOWAIT);
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}
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