[RFC PATCH 14/24] erofs: add block mapping capability in Rust

Yiyang Wu
2024-09-16T13:57:06Z

Implement block mapping in rust and implement map iterators
over Inode which will be used in data access.

Signed-off-by: Yiyang Wu <toolmanp@tlmp.cc>
---
fs/erofs/rust/erofs_sys/map.rs | 54 +++++++++++
fs/erofs/rust/erofs_sys/superblock.rs | 129 ++++++++++++++++++++++++++
2 files changed, 183 insertions(+)

diff --git a/fs/erofs/rust/erofs_sys/map.rs b/fs/erofs/rust/erofs_sys/map.rs
index 757e8083c8f1..f56f31cefcd5 100644
--- a/fs/erofs/rust/erofs_sys/map.rs
+++ b/fs/erofs/rust/erofs_sys/map.rs
@@ -1,7 +1,10 @@
// Copyright 2024 Yiyang Wu
// SPDX-License-Identifier: MIT or GPL-2.0-or-later

+use super::inode::*;
+use super::superblock::*;
use super::*;
+
pub(crate) const MAP_MAPPED: u32 = 0x0001;
pub(crate) const MAP_META: u32 = 0x0002;
pub(crate) const MAP_ENCODED: u32 = 0x0004;
@@ -43,3 +46,54 @@ fn from(value: MapType) -> Self {
}

pub(crate) type MapResult = PosixResult<Map>;
+
+/// Iterates over the data map represented by an inode.
+pub(crate) struct MapIter<'a, 'b, FS, I>
+where
+ FS: FileSystem,
+ I: Inode,
+{
+ fs: &'a FS,
+ inode: &'b I,
+ offset: Off,
+ len: Off,
+}
+
+impl<'a, 'b, FS, I> MapIter<'a, 'b, FS, I>
+where
+ FS: FileSystem,
+ I: Inode,
+{
+ pub(crate) fn new(fs: &'a FS, inode: &'b I, offset: Off) -> Self {
+ Self {
+ fs,
+ inode,
+ offset,
+ len: inode.info().file_size(),
+ }
+ }
+}
+
+impl<'a, 'b, FS, I> Iterator for MapIter<'a, 'b, FS, I>
+where
+ FS: FileSystem,
+ I: Inode,
+{
+ type Item = MapResult;
+ fn next(&mut self) -> Option<Self::Item> {
+ if self.offset >= self.len {
+ None
+ } else {
+ let result = self.fs.map(self.inode, self.offset);
+ match result {
+ Ok(m) => {
+ let accessor = self.fs.superblock().blk_access(m.physical.start);
+ let len = m.physical.len.min(accessor.len);
+ self.offset += len;
+ Some(Ok(m))
+ }
+ Err(e) => Some(Err(e)),
+ }
+ }
+ }
+}
diff --git a/fs/erofs/rust/erofs_sys/superblock.rs b/fs/erofs/rust/erofs_sys/superblock.rs
index 940ab0b03a26..fc6b3cb00b18 100644
--- a/fs/erofs/rust/erofs_sys/superblock.rs
+++ b/fs/erofs/rust/erofs_sys/superblock.rs
@@ -8,8 +8,11 @@
use super::data::*;
use super::devices::*;
use super::inode::*;
+use super::map::*;
use super::*;

+use crate::round;
+
/// The ondisk superblock structure.
#[derive(Debug, Clone, Copy, Default)]
#[repr(C)]
@@ -135,6 +138,10 @@ pub(crate) fn blk_round_up(&self, addr: Off) -> Blk {
pub(crate) fn iloc(&self, nid: Nid) -> Off {
self.blkpos(self.meta_blkaddr) + ((nid as Off) << (5 as Off))
}
+ pub(crate) fn chunk_access(&self, format: ChunkFormat, address: Off) -> Accessor {
+ let chunkbits = format.chunkbits() + self.blkszbits as u16;
+ Accessor::new(address, chunkbits as Off)
+ }
}

pub(crate) trait FileSystem
@@ -145,6 +152,128 @@ pub(crate) trait FileSystem
fn backend(&self) -> &dyn Backend;
fn as_filesystem(&self) -> &dyn FileSystem;
fn device_info(&self) -> &DeviceInfo;
+ fn flatmap(&self, inode: &I, offset: Off, inline: bool) -> MapResult {
+ let sb = self.superblock();
+ let nblocks = sb.blk_round_up(inode.info().file_size());
+ let blkaddr = match inode.info().spec() {
+ Spec::RawBlk(blkaddr) => Ok(blkaddr),
+ _ => Err(EUCLEAN),
+ }?;
+
+ let lastblk = if inline { nblocks - 1 } else { nblocks };
+ if offset < sb.blkpos(lastblk) {
+ let len = inode.info().file_size().min(sb.blkpos(lastblk)) - offset;
+ Ok(Map {
+ logical: Segment { start: offset, len },
+ physical: Segment {
+ start: sb.blkpos(blkaddr) + offset,
+ len,
+ },
+ algorithm_format: 0,
+ device_id: 0,
+ map_type: MapType::Normal,
+ })
+ } else if inline {
+ let len = inode.info().file_size() - offset;
+ let accessor = sb.blk_access(offset);
+ Ok(Map {
+ logical: Segment { start: offset, len },
+ physical: Segment {
+ start: sb.iloc(inode.nid())
+ + inode.info().inode_size()
+ + inode.info().xattr_size()
+ + accessor.off,
+ len,
+ },
+ algorithm_format: 0,
+ device_id: 0,
+ map_type: MapType::Meta,
+ })
+ } else {
+ Err(EUCLEAN)
+ }
+ }
+
+ fn chunk_map(&self, inode: &I, offset: Off) -> MapResult {
+ let sb = self.superblock();
+ let chunkformat = match inode.info().spec() {
+ Spec::Chunk(chunkformat) => Ok(chunkformat),
+ _ => Err(EUCLEAN),
+ }?;
+ let accessor = sb.chunk_access(chunkformat, offset);
+
+ if chunkformat.is_chunkindex() {
+ let unit = size_of::<ChunkIndex>() as Off;
+ let pos = round!(
+ UP,
+ self.superblock().iloc(inode.nid())
+ + inode.info().inode_size()
+ + inode.info().xattr_size()
+ + unit * accessor.nr,
+ unit
+ );
+ let mut buf = [0u8; size_of::<ChunkIndex>()];
+ self.backend().fill(&mut buf, pos)?;
+ let chunk_index = ChunkIndex::from(buf);
+ if chunk_index.blkaddr == u32::MAX {
+ Err(EUCLEAN)
+ } else {
+ Ok(Map {
+ logical: Segment {
+ start: accessor.base + accessor.off,
+ len: accessor.len,
+ },
+ physical: Segment {
+ start: sb.blkpos(chunk_index.blkaddr) + accessor.off,
+ len: accessor.len,
+ },
+ algorithm_format: 0,
+ device_id: chunk_index.device_id & self.device_info().mask,
+ map_type: MapType::Normal,
+ })
+ }
+ } else {
+ let unit = 4;
+ let pos = round!(
+ UP,
+ sb.iloc(inode.nid())
+ + inode.info().inode_size()
+ + inode.info().xattr_size()
+ + unit * accessor.nr,
+ unit
+ );
+ let mut buf = [0u8; 4];
+ self.backend().fill(&mut buf, pos)?;
+ let blkaddr = u32::from_le_bytes(buf);
+ let len = accessor.len.min(inode.info().file_size() - offset);
+ if blkaddr == u32::MAX {
+ Err(EUCLEAN)
+ } else {
+ Ok(Map {
+ logical: Segment {
+ start: accessor.base + accessor.off,
+ len,
+ },
+ physical: Segment {
+ start: sb.blkpos(blkaddr) + accessor.off,
+ len,
+ },
+ algorithm_format: 0,
+ device_id: 0,
+ map_type: MapType::Normal,
+ })
+ }
+ }
+ }
+
+ fn map(&self, inode: &I, offset: Off) -> MapResult {
+ match inode.info().format().layout() {
+ Layout::FlatInline => self.flatmap(inode, offset, true),
+ Layout::FlatPlain => self.flatmap(inode, offset, false),
+ Layout::Chunk => self.chunk_map(inode, offset),
+ _ => todo!(),
+ }
+ }
}

pub(crate) struct SuperblockInfo<I, C, T>
--
2.46.0