Add support for converting from VmFrame to VmSegment

Cargo.lock

@@ -70,6 +70,7 @@ checksum = "d92bec98840b8f03a5ff5413de5293bfcd8bf96467cf5452609f939ec6f5de16"
 name = "aster-block"
 version = "0.1.0"
 dependencies = [
+ "align_ext",
  "aster-frame",
  "aster-util",
  "bitflags 1.3.2",

framework/aster-frame/src/vm/frame.rs

@@ -314,17 +314,17 @@ impl Drop for VmFrame {
 /// ```
 #[derive(Debug, Clone)]
 pub struct VmSegment {
-    inner: Arc<Inner>,
+    inner: VmSegmentInner,
     range: Range<usize>,
 }
 
-#[derive(Debug)]
-struct Inner {
-    start_frame_index: Paddr,
+#[derive(Debug, Clone)]
+struct VmSegmentInner {
+    start_frame_index: Arc<Paddr>,
     nframes: usize,
 }
 
-impl Inner {
+impl VmSegmentInner {
     /// Creates the inner part of 'VmSegment'.
     ///
     /// # Safety
@@ -333,14 +333,13 @@ impl Inner {
     unsafe fn new(paddr: Paddr, nframes: usize, flags: VmFrameFlags) -> Self {
         assert_eq!(paddr % PAGE_SIZE, 0);
         Self {
-            start_frame_index: (paddr / PAGE_SIZE).bitor(flags.bits),
+            start_frame_index: Arc::new((paddr / PAGE_SIZE).bitor(flags.bits)),
             nframes,
         }
     }
 
     fn start_frame_index(&self) -> usize {
-        self.start_frame_index
-            .bitand(VmFrameFlags::all().bits().not())
+        (*self.start_frame_index).bitand(VmFrameFlags::all().bits().not())
     }
 
     fn start_paddr(&self) -> Paddr {
@@ -364,7 +363,7 @@ impl VmSegment {
     /// as part of either a `VmFrame` or `VmSegment`.
     pub(crate) unsafe fn new(paddr: Paddr, nframes: usize, flags: VmFrameFlags) -> Self {
         Self {
-            inner: Arc::new(Inner::new(paddr, nframes, flags)),
+            inner: VmSegmentInner::new(paddr, nframes, flags),
             range: 0..nframes,
         }
     }
@@ -407,7 +406,7 @@ impl VmSegment {
     }
 
     fn need_dealloc(&self) -> bool {
-        (self.inner.start_frame_index & VmFrameFlags::NEED_DEALLOC.bits()) != 0
+        (*self.inner.start_frame_index & VmFrameFlags::NEED_DEALLOC.bits()) != 0
     }
 
     fn start_frame_index(&self) -> usize {
@@ -459,7 +458,7 @@ impl VmIo for VmSegment {
 
 impl Drop for VmSegment {
     fn drop(&mut self) {
-        if self.need_dealloc() && Arc::strong_count(&self.inner) == 1 {
+        if self.need_dealloc() && Arc::strong_count(&self.inner.start_frame_index) == 1 {
             // Safety: the range of contiguous page frames is valid.
             unsafe {
                 frame_allocator::dealloc_contiguous(
@@ -471,6 +470,18 @@ impl Drop for VmSegment {
     }
 }
 
+impl From<VmFrame> for VmSegment {
+    fn from(frame: VmFrame) -> Self {
+        Self {
+            inner: VmSegmentInner {
+                start_frame_index: frame.frame_index.clone(),
+                nframes: 1,
+            },
+            range: 0..1,
+        }
+    }
+}
+
 /// VmReader is a reader for reading data from a contiguous range of memory.
 ///
 /// # Example

kernel/comps/block/Cargo.toml

@@ -10,6 +10,7 @@ bitflags = "1.3"
 spin = "0.9.4"
 pod = { git = "https://github.com/asterinas/pod", rev = "d7dba56" }
 aster-frame = { path = "../../../framework/aster-frame" }
+align_ext = { path = "../../../framework/libs/align_ext" }
 aster-util = { path = "../../libs/aster-util" }
 int-to-c-enum = { path = "../../libs/int-to-c-enum" }
 component = { path = "../../libs/comp-sys/component" }

kernel/comps/block/src/bio.rs

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
+use align_ext::AlignExt;
 use aster_frame::{
     sync::WaitQueue,
     vm::{VmFrame, VmReader, VmSegment, VmWriter},
@@ -358,29 +359,27 @@ pub enum BioStatus {
 #[derive(Debug, Clone)]
 pub struct BioSegment {
     /// The contiguous pages on which this segment resides.
-    pages: Pages,
-    /// The offset (in bytes) relative to the first page.
+    pages: VmSegment,
+    /// The starting offset (in bytes) within the first page.
+    /// The offset should always be aligned to the sector size and
+    /// must not exceed the size of a single page.
     offset: AlignedUsize<SECTOR_SIZE>,
-    // The length (in bytes), may cross pages.
+    /// The total length (in bytes).
+    /// The length can span multiple pages and should be aligned to
+    /// the sector size.
     len: AlignedUsize<SECTOR_SIZE>,
 }
 
 const SECTOR_SIZE: u16 = super::SECTOR_SIZE as u16;
 
-#[derive(Debug, Clone)]
-enum Pages {
-    Frame(VmFrame),
-    Segment(VmSegment),
-}
-
 impl<'a> BioSegment {
     /// Constructs a new `BioSegment` from `VmSegment`.
     pub fn from_segment(segment: VmSegment, offset: usize, len: usize) -> Self {
         assert!(offset + len <= segment.nbytes());
 
         Self {
-            pages: Pages::Segment(segment),
-            offset: AlignedUsize::<SECTOR_SIZE>::new(offset).unwrap(),
+            pages: segment.range(frame_range(&(offset..offset + len))),
+            offset: AlignedUsize::<SECTOR_SIZE>::new(offset % super::BLOCK_SIZE).unwrap(),
             len: AlignedUsize::<SECTOR_SIZE>::new(len).unwrap(),
         }
     }
@@ -390,7 +389,7 @@ impl<'a> BioSegment {
         assert!(offset + len <= super::BLOCK_SIZE);
 
         Self {
-            pages: Pages::Frame(frame),
+            pages: VmSegment::from(frame),
             offset: AlignedUsize::<SECTOR_SIZE>::new(offset).unwrap(),
             len: AlignedUsize::<SECTOR_SIZE>::new(len).unwrap(),
         }
@@ -406,25 +405,39 @@ impl<'a> BioSegment {
         self.len.value()
     }
 
+    /// Returns the offset (in bytes) within the first page.
+    pub fn offset(&self) -> usize {
+        self.offset.value()
+    }
+
+    /// Returns the contiguous pages on which this segment resides.
+    pub fn pages(&self) -> &VmSegment {
+        &self.pages
+    }
+
     /// Returns a reader to read data from it.
     pub fn reader(&'a self) -> VmReader<'a> {
-        let reader = match &self.pages {
-            Pages::Segment(segment) => segment.reader(),
-            Pages::Frame(frame) => frame.reader(),
-        };
-        reader.skip(self.offset.value()).limit(self.len.value())
+        self.pages
+            .reader()
+            .skip(self.offset.value())
+            .limit(self.len.value())
     }
 
     /// Returns a writer to write data into it.
     pub fn writer(&'a self) -> VmWriter<'a> {
-        let writer = match &self.pages {
-            Pages::Segment(segment) => segment.writer(),
-            Pages::Frame(frame) => frame.writer(),
-        };
-        writer.skip(self.offset.value()).limit(self.len.value())
+        self.pages
+            .writer()
+            .skip(self.offset.value())
+            .limit(self.len.value())
     }
 }
 
+fn frame_range(byte_range: &Range<usize>) -> Range<usize> {
+    let start = byte_range.start.align_down(super::BLOCK_SIZE);
+    let end = byte_range.end.align_up(super::BLOCK_SIZE);
+    (start / super::BLOCK_SIZE)..(end / super::BLOCK_SIZE)
+}
+
 /// An aligned unsigned integer number.
 ///
 /// An instance of `AlignedUsize<const N: u16>` is guaranteed to have a value that is a multiple