mirror of
https://github.com/panpaul/tiny_os
synced 2024-09-20 09:45:19 +08:00
feat: allow to reserve space in freelist
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bca4e37ef2
commit
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@ -1,5 +1,6 @@
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// adapted from https://os.phil-opp.com/allocator-designs/#linked-list-allocator
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// adapted from https://os.phil-opp.com/allocator-designs/#linked-list-allocator
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use crate::utils::then::Then;
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use crate::vspace::addr::{AddressOps, PhysAddr};
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use crate::vspace::addr::{AddressOps, PhysAddr};
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use core::alloc::{GlobalAlloc, Layout};
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use core::alloc::{GlobalAlloc, Layout};
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use spin::Mutex;
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use spin::Mutex;
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@ -21,6 +22,24 @@ impl ListNode {
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fn end_addr(&self) -> PhysAddr {
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fn end_addr(&self) -> PhysAddr {
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self.start_addr() + self.size
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self.start_addr() + self.size
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}
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}
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fn fit(&self, size: usize, align: usize) -> Result<PhysAddr, ()> {
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let alloc_start = self.start_addr().align_up(align);
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let alloc_end = alloc_start + size;
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if alloc_end > self.end_addr() {
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return Err(());
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}
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let excess_size = (self.end_addr() - alloc_end).as_usize();
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if excess_size > 0 && excess_size < core::mem::size_of::<ListNode>() {
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// GlobalAlloc requires that dealloc be called with the original size and alignment,
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// so we can't "waste" the remaining space and must return an error.
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return Err(());
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}
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Ok(alloc_start)
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}
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}
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}
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struct FreeList {
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struct FreeList {
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@ -34,7 +53,47 @@ impl FreeList {
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}
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}
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}
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}
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unsafe fn add_free_region(&mut self, start: PhysAddr, size: usize) {
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fn alloc_node<F, V>(&mut self, mut predicate: F) -> Option<(&'static mut ListNode, V)>
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where F: FnMut(&mut ListNode) -> Result<V, ()> {
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let mut current = &mut self.head;
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while let Some(ref mut region) = current.next {
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if let Ok(v) = predicate(region) {
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let next = region.next.take();
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let ret = Some((current.next.take().unwrap(), v));
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current.next = next;
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return ret;
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} else {
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current = current.next.as_mut().unwrap();
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}
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}
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None
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}
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fn align_layout(layout: Layout) -> (usize, usize) {
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let layout = layout
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.align_to(core::mem::align_of::<ListNode>())
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.expect("adjusting alignment failed")
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.pad_to_align();
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let size = layout.size().max(core::mem::size_of::<ListNode>());
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(size, layout.align())
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}
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unsafe fn alloc(&mut self, layout: Layout) -> *mut u8 {
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let (size, align) = Self::align_layout(layout);
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if let Some((region, alloc_start)) = self.alloc_node(|region| region.fit(size, align)) {
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let alloc_end = alloc_start + size;
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let excess_size = (region.end_addr() - alloc_end).as_usize();
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if excess_size > 0 {
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self.dealloc(alloc_end, excess_size);
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}
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alloc_start.as_mut_ptr()
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} else {
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core::ptr::null_mut()
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}
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}
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unsafe fn dealloc(&mut self, start: PhysAddr, size: usize) {
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assert_eq!(start.align_up(core::mem::align_of::<ListNode>()), start);
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assert_eq!(start.align_up(core::mem::align_of::<ListNode>()), start);
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assert!(size >= core::mem::size_of::<ListNode>());
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assert!(size >= core::mem::size_of::<ListNode>());
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@ -45,39 +104,31 @@ impl FreeList {
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self.head.next = Some(&mut *node_ptr);
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self.head.next = Some(&mut *node_ptr);
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}
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}
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fn find_region(
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pub fn reserve(&mut self, start: PhysAddr, size: usize) {
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&mut self,
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if let Some((region, _)) = self
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size: usize,
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.alloc_node(|region| (region.start_addr() <= start).chain(|| region.fit(size, 1), ()))
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align: usize,
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{
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) -> Option<(&'static mut ListNode, PhysAddr)> {
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/* layout
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let mut current = &mut self.head;
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* region: | before | [start +: size] | after |
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while let Some(ref mut region) = current.next {
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* ^ ^ ^ ^ region.end_addr()
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if let Ok(alloc_start) = Self::alloc_from_region(®ion, size, align) {
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* | | alloc_start |
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let next = region.next.take();
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* | | alloc_end
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let ret = Some((current.next.take().unwrap(), alloc_start));
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* | region.start_addr()
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current.next = next;
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*/
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return ret;
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} else {
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let region_start = region.start_addr();
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current = current.next.as_mut().unwrap();
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let region_end = region.end_addr();
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let before_size = (start - region_start).as_usize();
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if before_size > 0 {
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unsafe { self.dealloc(region_start, before_size) }
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}
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let after_size = (region_end - (start + size)).as_usize();
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if after_size > 0 {
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unsafe { self.dealloc(start + size, after_size) }
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}
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}
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}
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}
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None
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}
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fn alloc_from_region(region: &ListNode, size: usize, align: usize) -> Result<PhysAddr, ()> {
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let alloc_start = region.start_addr().align_up(align);
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let alloc_end = alloc_start + size;
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if alloc_end > region.end_addr() {
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return Err(());
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}
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let excess_size = (region.end_addr() - alloc_end).as_usize();
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if excess_size > 0 && excess_size < core::mem::size_of::<ListNode>() {
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return Err(());
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}
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Ok(alloc_start)
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}
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}
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}
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}
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@ -88,42 +139,21 @@ pub struct FreeListAllocator {
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impl FreeListAllocator {
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impl FreeListAllocator {
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pub fn new(start: PhysAddr, size: usize) -> Self {
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pub fn new(start: PhysAddr, size: usize) -> Self {
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let mut list = FreeList::new();
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let mut list = FreeList::new();
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unsafe { list.add_free_region(start, size) }
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unsafe { list.dealloc(start, size) }
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Self {
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Self {
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list: Mutex::new(list),
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list: Mutex::new(list),
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}
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}
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}
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}
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fn size_align(layout: Layout) -> (usize, usize) {
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let layout = layout
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.align_to(core::mem::align_of::<ListNode>())
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.expect("adjusting alignment failed")
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.pad_to_align();
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let size = layout.size().max(core::mem::size_of::<ListNode>());
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(size, layout.align())
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}
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}
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}
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unsafe impl GlobalAlloc for FreeListAllocator {
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unsafe impl GlobalAlloc for FreeListAllocator {
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unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
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unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
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let (size, align) = Self::size_align(layout);
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self.list.lock().alloc(layout)
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let mut allocator = self.list.lock();
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if let Some((region, alloc_start)) = allocator.find_region(size, align) {
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let alloc_end = alloc_start + size;
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let excess_size = (region.end_addr() - alloc_end).as_usize();
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if excess_size > 0 {
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allocator.add_free_region(alloc_end, excess_size);
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}
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alloc_start.as_mut_ptr()
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} else {
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core::ptr::null_mut()
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}
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}
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}
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unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
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unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
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let (size, _) = Self::size_align(layout);
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let (size, _) = FreeList::align_layout(layout);
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self.list.lock().add_free_region(PhysAddr::from(ptr), size)
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self.list.lock().dealloc(PhysAddr::from(ptr), size)
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}
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}
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}
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}
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@ -158,4 +188,36 @@ mod tests {
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unsafe { allocator.alloc(Layout::from_size_align(PAGE_SIZE, PAGE_SIZE).unwrap()) };
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unsafe { allocator.alloc(Layout::from_size_align(PAGE_SIZE, PAGE_SIZE).unwrap()) };
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assert_eq!(ptr as usize, BASE.as_usize());
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assert_eq!(ptr as usize, BASE.as_usize());
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}
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}
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#[test_case]
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fn test_freelist_reserve() {
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const BASE: PhysAddr = PhysAddr(0x80300000);
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let allocator = FreeListAllocator::new(BASE, 32 * PAGE_SIZE);
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allocator
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.list
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.lock()
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.reserve(BASE + 4 * PAGE_SIZE, 4 * PAGE_SIZE);
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let mut cnt = 32 - 4;
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loop {
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let ptr =
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unsafe { allocator.alloc(Layout::from_size_align(PAGE_SIZE, PAGE_SIZE).unwrap()) };
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if ptr.is_null() {
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assert_eq!(cnt, 0);
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break;
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}
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let ptr = PhysAddr::from(ptr);
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assert!(
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!(BASE + 4 * PAGE_SIZE <= ptr && ptr < BASE + (4 + 4) * PAGE_SIZE),
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"Bad alloc: returned ptr: {:?}, reserved range: {:?}->{:?}",
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ptr,
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BASE + 4 * PAGE_SIZE,
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BASE + (4 + 4) * PAGE_SIZE
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);
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cnt -= 1;
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}
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}
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}
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}
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