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use crate::block_device::{BlockDevice, BLOCK_SIZE};
use crate::disk::block::Block;
use crate::disk::inode::Inode;
use crate::AyaFS;
use and_then_some::BoolExt;
use log::debug;
use lru::LruCache;
use std::num::NonZeroUsize;
use std::sync::Arc;
#[derive(Clone)]
pub struct CachedBlock<T: Block> {
pub block: T,
pub index: usize,
pub dirty: bool,
}
impl<T: Block> CachedBlock<T> {
fn cast<U: Block>(&self) -> CachedBlock<U> {
unsafe { std::mem::transmute_copy(&self) }
}
}
pub fn convert_mut<U: Block, T: Block>(input_block: &mut CachedBlock<U>) -> &mut CachedBlock<T> {
let ptr = input_block as *const CachedBlock<U> as *mut u8;
let block = ptr.cast::<CachedBlock<T>>();
unsafe { &mut *block }
}
pub fn convert<U: Block, T: Block>(input_block: &CachedBlock<U>) -> &CachedBlock<T> {
let ptr = input_block as *const CachedBlock<U> as *mut u8;
let block = ptr.cast::<CachedBlock<T>>();
unsafe { &*block }
}
pub(crate) struct BlockCache<T: Block> {
device: Arc<dyn BlockDevice>,
cache: LruCache<usize, CachedBlock<T>>,
}
impl<T: Block> BlockCache<T> {
pub(crate) fn new(device: Arc<dyn BlockDevice>, cache_size: usize) -> Self {
Self {
device,
cache: LruCache::new(NonZeroUsize::new(cache_size).unwrap()),
}
}
pub(crate) fn load_block(&mut self, index: usize) -> bool {
if self.cache.contains(&index) == false {
let mut buffer = [0u8; BLOCK_SIZE];
self.device.read(index, &mut buffer);
let block: T = unsafe { std::mem::transmute_copy(&buffer) };
let cached_block = CachedBlock {
block,
index,
dirty: false,
};
if let Some((old_index, old_block)) = self.cache.push(index, cached_block) {
assert_ne!(old_index, index); // 只有 block 不在 cache 里的时候才会插入
if old_block.dirty {
let old_block_ptr = &old_block.block as *const T as *mut u8;
let old_block_buffer =
unsafe { std::slice::from_raw_parts(old_block_ptr, BLOCK_SIZE) };
self.device.write(old_index, old_block_buffer);
}
}
}
true
}
/// 从 LRU cache 里获取一个 block 的引用, 如果没有在 cache 中会加载.
/// 这个函数不应该返回 None
pub(crate) fn get_block<U: Block>(&mut self, index: usize) -> Option<&CachedBlock<U>> {
if !self.cache.contains(&index) {
self.load_block(index);
}
self.cache.get(&index).map(convert::<T,U>)
}
/// 从 LRU cache 里获取一个 block 的可变引用, 如果没有在 cache 中会加载.
/// 这个函数不应该返回 None
pub(crate) fn get_block_mut<U: Block>(&mut self, index: usize) -> Option<&mut CachedBlock<U>> {
if !self.cache.contains(&index) {
self.load_block(index);
}
self.cache.get_mut(&index).map(|block| {
block.dirty = true;
convert_mut::<T, U>(block)
})
}
/// 从 LRU cache 中读取一个 block 的引用, *不会* 影响 LRU cache 的结构, 如果没有在 cache 中不会加载.
pub(crate) fn peek_block<U: Block>(&self, index: usize) -> Option<&CachedBlock<U>> {
self.cache.peek(&index).map(convert::<T, U>)
}
/// 从 LRU cache 中读取一个 block 的可变引用, *不会* 影响 LRU cache 的结构, 如果没有在 cache 中不会加载.
pub(crate) fn peek_block_mut<U: Block>(&mut self, index: usize) -> Option<&mut CachedBlock<U>> {
self.cache.peek_mut(&index).map(convert_mut::<T, U>)
}
pub(crate) fn update_block<U: Block>(&mut self, block: CachedBlock<U>) -> bool {
if self.cache.contains(&block.index) {
let mut data_block = convert::<U, T>(&block).clone();
data_block.dirty = true; // TODO 需要把显式写回的都标记为 dirty 吗
self.cache.push(block.index, data_block);
true
} else {
false
}
}
fn pop(&mut self, entry: &usize) -> Option<CachedBlock<T>> {
self.cache.pop(entry)
}
}
impl AyaFS {
pub(crate) fn load_block(&mut self, index: usize) -> bool {
if !self.data_bitmap.query(index) {
self.cached_blocks.pop(&index);
// deallocate 时只更新 bitmap 没有动 cache, lazy 地驱逐 cache 中的无效 entry.
return false;
}
self.cached_blocks.load_block(index)
}
pub(crate) fn get_block<T: Block>(&mut self, index: usize) -> Option<&CachedBlock<T>> {
self.data_bitmap
.query(index)
.then(|| self.cached_blocks.get_block::<T>(index).unwrap())
// 返回 None 当且仅当 data_bitmap 中这个 block 为 invalid
}
pub(crate) fn get_block_mut<T: Block>(&mut self, index: usize) -> Option<&mut CachedBlock<T>> {
self.data_bitmap
.query(index)
.then(|| self.cached_blocks.get_block_mut::<T>(index).unwrap())
// 返回 None 当且仅当 data_bitmap 中这个 block 为 invalid
}
pub(crate) fn peek_block<T: Block>(&self, index: usize) -> Option<&CachedBlock<T>> {
self.data_bitmap
.query(index)
.then(|| self.cached_blocks.peek_block::<T>(index).unwrap())
// 返回 None 当且仅当 data_bitmap 中这个 block 为 invalid
}
pub(crate) fn peek_block_mut<T: Block>(&mut self, index: usize) -> Option<&mut CachedBlock<T>> {
self.data_bitmap
.query(index)
.then(|| self.cached_blocks.peek_block_mut::<T>(index).unwrap())
// 返回 None 当且仅当 data_bitmap 中这个 block 为 invalid
}
pub(crate) fn update_block<T: Block>(&mut self, block: CachedBlock<T>) -> bool {
self.cached_blocks.update_block(block)
}
}
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