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Use frame metadada for page cache

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This commit is contained in:
Zhang Junyang
2024-12-25 13:06:48 +08:00
committed by Tate, Hongliang Tian
parent cdac59beda
commit f332797084
1 changed files with 94 additions and 58 deletions
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152
kernel/src/fs/utils/page_cache.rs
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@ -2,13 +2,20 @@
#![allow(dead_code)]
use core::{iter, ops::Range};
use core::{
iter,
ops::Range,
sync::atomic::{AtomicU8, Ordering},
};
use align_ext::AlignExt;
use aster_block::bio::{BioStatus, BioWaiter};
use aster_rights::Full;
use lru::LruCache;
use ostd::mm::{DynUFrame, Frame, FrameAllocOptions, VmIo};
use ostd::{
impl_untyped_frame_meta_for,
mm::{DynUFrame, Frame, FrameAllocOptions, UntypedMem, VmIo},
};
use crate::{
prelude::*,
@ -242,7 +249,7 @@ impl ReadaheadState {
/// Waits for the previous readahead.
pub fn wait_for_prev_readahead(
&mut self,
pages: &mut MutexGuard<LruCache<usize, Page>>,
pages: &mut MutexGuard<LruCache<usize, CachePage>>,
) -> Result<()> {
if matches!(self.waiter.wait(), Some(BioStatus::Complete)) {
let Some(window) = &self.ra_window else {
@ -250,7 +257,7 @@ impl ReadaheadState {
};
for idx in window.readahead_range() {
if let Some(page) = pages.get_mut(&idx) {
page.set_state(PageState::UpToDate);
page.store_state(PageState::UpToDate);
}
}
self.waiter.clear();
@ -297,20 +304,20 @@ impl ReadaheadState {
/// Sends the relevant read request and sets the relevant page in the page cache to `Uninit`.
pub fn conduct_readahead(
&mut self,
pages: &mut MutexGuard<LruCache<usize, Page>>,
pages: &mut MutexGuard<LruCache<usize, CachePage>>,
backend: Arc<dyn PageCacheBackend>,
) -> Result<()> {
let Some(window) = &self.ra_window else {
return_errno!(Errno::EINVAL)
};
for async_idx in window.readahead_range() {
let mut async_page = Page::alloc()?;
let pg_waiter = backend.read_page_async(async_idx, async_page.frame().into())?;
let mut async_page = CachePage::alloc()?;
let pg_waiter = backend.read_page_async(async_idx, (&async_page).into())?;
if pg_waiter.nreqs() > 0 {
self.waiter.concat(pg_waiter);
} else {
// Some backends (e.g. RamFS) do not issue requests, but fill the page directly.
async_page.set_state(PageState::UpToDate);
async_page.store_state(PageState::UpToDate);
}
pages.put(async_idx, async_page);
}
@ -324,7 +331,7 @@ impl ReadaheadState {
}
struct PageCacheManager {
pages: Mutex<LruCache<usize, Page>>,
pages: Mutex<LruCache<usize, CachePage>>,
backend: Weak<dyn PageCacheBackend>,
ra_state: Mutex<ReadaheadState>,
}
@ -360,8 +367,8 @@ impl PageCacheManager {
let backend_npages = backend.npages();
for idx in page_idx_range.start..page_idx_range.end {
if let Some(page) = pages.peek(&idx) {
if *page.state() == PageState::Dirty && idx < backend_npages {
let waiter = backend.write_page_async(idx, page.frame().into())?;
if page.load_state() == PageState::Dirty && idx < backend_npages {
let waiter = backend.write_page_async(idx, page.into())?;
bio_waiter.concat(waiter);
}
}
@ -376,7 +383,7 @@ impl PageCacheManager {
.iter_mut()
.filter(|(idx, _)| page_idx_range.contains(*idx))
{
page.set_state(PageState::UpToDate);
page.store_state(PageState::UpToDate);
}
Ok(())
}
@ -395,28 +402,28 @@ impl PageCacheManager {
// 3. The requested page is on disk, need a sync read operation here.
let frame = if let Some(page) = pages.get(&idx) {
// Cond 1 & 2.
if let PageState::Uninit = page.state() {
if let PageState::Uninit = page.load_state() {
// Cond 2: We should wait for the previous readahead.
// If there is no previous readahead, an error must have occurred somewhere.
assert!(ra_state.request_number() != 0);
ra_state.wait_for_prev_readahead(&mut pages)?;
pages.get(&idx).unwrap().frame().clone()
pages.get(&idx).unwrap().clone()
} else {
// Cond 1.
page.frame().clone()
page.clone()
}
} else {
// Cond 3.
// Conducts the sync read operation.
let page = if idx < backend.npages() {
let mut page = Page::alloc()?;
backend.read_page(idx, page.frame().into())?;
page.set_state(PageState::UpToDate);
let mut page = CachePage::alloc()?;
backend.read_page(idx, (&page).into())?;
page.store_state(PageState::UpToDate);
page
} else {
Page::alloc_zero()?
CachePage::alloc_zero()?
};
let frame = page.frame().clone();
let frame = page.clone();
pages.put(idx, page);
frame
};
@ -445,7 +452,7 @@ impl Pager for PageCacheManager {
fn update_page(&self, idx: usize) -> Result<()> {
let mut pages = self.pages.lock();
if let Some(page) = pages.get_mut(&idx) {
page.set_state(PageState::Dirty);
page.store_state(PageState::Dirty);
} else {
warn!("The page {} is not in page cache", idx);
}
@ -456,12 +463,12 @@ impl Pager for PageCacheManager {
fn decommit_page(&self, idx: usize) -> Result<()> {
let page_result = self.pages.lock().pop(&idx);
if let Some(page) = page_result {
if let PageState::Dirty = page.state() {
if let PageState::Dirty = page.load_state() {
let Some(backend) = self.backend.upgrade() else {
return Ok(());
};
if idx < backend.npages() {
backend.write_page(idx, page.frame().into())?;
backend.write_page(idx, (&page).into())?;
}
}
}
@ -471,67 +478,96 @@ impl Pager for PageCacheManager {
fn commit_overwrite(&self, idx: usize) -> Result<DynUFrame> {
if let Some(page) = self.pages.lock().get(&idx) {
return Ok(page.frame.clone().into());
return Ok(page.clone().into());
}
let page = Page::alloc_zero()?;
Ok(self
.pages
.lock()
.get_or_insert(idx, || page)
.frame
.clone()
.into())
let page = CachePage::alloc_zero()?;
Ok(self.pages.lock().get_or_insert(idx, || page).clone().into())
}
}
/// A page in the page cache.
pub type CachePage = Frame<CachePageMeta>;
/// Metadata for a page in the page cache.
#[derive(Debug)]
struct Page {
frame: Frame<()>,
state: PageState,
pub struct CachePageMeta {
pub state: AtomicPageState,
// TODO: Add a reverse mapping from the page to VMO for eviction.
}
impl Page {
pub fn alloc() -> Result<Self> {
let frame = FrameAllocOptions::new().zeroed(false).alloc_frame()?;
Ok(Self {
frame,
state: PageState::Uninit,
})
impl_untyped_frame_meta_for!(CachePageMeta);
pub trait CachePageExt {
fn metadata(&self) -> &CachePageMeta;
fn alloc() -> Result<CachePage> {
let meta = CachePageMeta {
state: AtomicPageState {
state: AtomicU8::new(PageState::Uninit as u8),
},
};
let page = FrameAllocOptions::new()
.zeroed(false)
.alloc_frame_with(meta)?;
Ok(page)
}
pub fn alloc_zero() -> Result<Self> {
let frame = FrameAllocOptions::new().alloc_frame()?;
Ok(Self {
frame,
state: PageState::Dirty,
})
fn alloc_zero() -> Result<CachePage> {
let page = Self::alloc()?;
page.writer().fill(0);
Ok(page)
}
pub fn frame(&self) -> &Frame<()> {
&self.frame
fn load_state(&self) -> PageState {
self.metadata().state.load(Ordering::Relaxed)
}
pub fn state(&self) -> &PageState {
&self.state
fn store_state(&mut self, new_state: PageState) {
self.metadata().state.store(new_state, Ordering::Relaxed);
}
}
pub fn set_state(&mut self, new_state: PageState) {
self.state = new_state;
impl CachePageExt for CachePage {
fn metadata(&self) -> &CachePageMeta {
self.meta()
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum PageState {
#[repr(u8)]
pub enum PageState {
/// `Uninit` indicates a new allocated page which content has not been initialized.
/// The page is available to write, not available to read.
Uninit,
Uninit = 0,
/// `UpToDate` indicates a page which content is consistent with corresponding disk content.
/// The page is available to read and write.
UpToDate,
UpToDate = 1,
/// `Dirty` indicates a page which content has been updated and not written back to underlying disk.
/// The page is available to read and write.
Dirty,
Dirty = 2,
}
/// A page state with atomic operations.
#[derive(Debug)]
pub struct AtomicPageState {
state: AtomicU8,
}
impl AtomicPageState {
pub fn load(&self, order: Ordering) -> PageState {
let val = self.state.load(order);
match val {
0 => PageState::Uninit,
1 => PageState::UpToDate,
2 => PageState::Dirty,
_ => unreachable!(),
}
}
pub fn store(&self, val: PageState, order: Ordering) {
self.state.store(val as u8, order);
}
}
/// This trait represents the backend for the page cache.