Revise the BlockDevice trait

kernel/aster-nix/src/fs/exfat/mod.rs

@@ -19,7 +19,7 @@ mod test {
 
     use aster_block::{
         bio::{BioEnqueueError, BioStatus, BioType, SubmittedBio},
-        BlockDevice,
+        BlockDevice, BlockDeviceMeta,
     };
     use ostd::{
         mm::{FrameAllocOptions, Segment, VmIo},
@@ -99,8 +99,11 @@ mod test {
             Ok(())
         }
 
-        fn max_nr_segments_per_bio(&self) -> usize {
+        fn metadata(&self) -> BlockDeviceMeta {
-            usize::MAX
+            BlockDeviceMeta {
+                max_nr_segments_per_bio: usize::MAX,
+                nr_sectors: self.sectors_count(),
+            }
         }
     }
     /// Exfat disk image

kernel/aster-nix/src/fs/ext2/fs.rs

@@ -36,7 +36,11 @@ impl Ext2 {
             let raw_super_block = block_device.read_val::<RawSuperBlock>(SUPER_BLOCK_OFFSET)?;
             SuperBlock::try_from(raw_super_block)?
         };
-        assert!(super_block.block_size() == BLOCK_SIZE);
+        assert_eq!(
+            super_block.block_size(),
+            BLOCK_SIZE,
+            "currently only support 4096-byte block size"
+        );
 
         let group_descriptors_segment = {
             let npages = ((super_block.block_groups_count() as usize)

kernel/comps/block/src/lib.rs

@@ -56,8 +56,19 @@ pub const SECTOR_SIZE: usize = 512;
 pub trait BlockDevice: Send + Sync + Any + Debug {
     /// Enqueues a new `SubmittedBio` to the block device.
     fn enqueue(&self, bio: SubmittedBio) -> Result<(), BioEnqueueError>;
-    /// Returns the upper limit for the number of segments per bio.
+
-    fn max_nr_segments_per_bio(&self) -> usize;
+    /// Returns the metadata of the block device.
+    fn metadata(&self) -> BlockDeviceMeta;
+}
+
+/// Metadata for a block device.
+#[derive(Debug, Clone, Copy)]
+pub struct BlockDeviceMeta {
+    /// The upper limit for the number of segments per bio.
+    pub max_nr_segments_per_bio: usize,
+    /// The total number of sectors of the block device.
+    pub nr_sectors: usize,
+    // Additional useful metadata can be added here in the future.
 }
 
 impl dyn BlockDevice {

kernel/comps/virtio/src/device/block/device.rs

@@ -6,6 +6,7 @@ use core::{fmt::Debug, hint::spin_loop, mem::size_of};
 use aster_block::{
     bio::{BioEnqueueError, BioStatus, BioType, SubmittedBio},
     request_queue::{BioRequest, BioRequestSingleQueue},
+    BlockDeviceMeta,
 };
 use aster_util::safe_ptr::SafePtr;
 use id_alloc::IdAlloc;
@@ -79,8 +80,12 @@ impl aster_block::BlockDevice for BlockDevice {
         self.queue.enqueue(bio)
     }
 
-    fn max_nr_segments_per_bio(&self) -> usize {
+    fn metadata(&self) -> BlockDeviceMeta {
-        self.queue.max_nr_segments_per_bio()
+        let device_config = self.device.config.read().unwrap();
+        BlockDeviceMeta {
+            max_nr_segments_per_bio: self.queue.max_nr_segments_per_bio(),
+            nr_sectors: device_config.capacity_sectors(),
+        }
     }
 }
 
@@ -101,6 +106,11 @@ impl DeviceInner {
     /// Creates and inits the device.
     pub fn init(mut transport: Box<dyn VirtioTransport>) -> Result<Arc<Self>, VirtioDeviceError> {
         let config = VirtioBlockConfig::new(transport.as_mut());
+        assert_eq!(
+            config.read().unwrap().block_size(),
+            VirtioBlockConfig::sector_size(),
+            "currently not support customized device logical block size"
+        );
         let num_queues = transport.num_queues();
         if num_queues != 1 {
             return Err(VirtioDeviceError::QueuesAmountDoNotMatch(num_queues, 1));

kernel/comps/virtio/src/device/block/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod device;
 
+use aster_block::SECTOR_SIZE;
 use aster_util::safe_ptr::SafePtr;
 use bitflags::bitflags;
 use int_to_c_enum::TryFromInt;
@@ -56,18 +57,32 @@ pub enum RespStatus {
 #[derive(Debug, Copy, Clone, Pod)]
 #[repr(C)]
 pub struct VirtioBlockConfig {
+    /// The number of 512-byte sectors.
     capacity: u64,
+    /// The maximum segment size.
     size_max: u64,
+    /// The geometry of the device.
     geometry: VirtioBlockGeometry,
+    /// The block size. If `logical_block_size` is not given in qemu cmdline,
+    /// `blk_size` will be set to sector size (512 bytes) by default.
     blk_size: u32,
+    /// The topology of the device.
     topology: VirtioBlockTopology,
+    /// Writeback mode.
     writeback: u8,
     unused0: [u8; 3],
+    /// The maximum discard sectors for one segment.
     max_discard_sectors: u32,
+    /// The maximum number of discard segments in a discard command.
     max_discard_seg: u32,
+    /// Discard commands must be aligned to this number of sectors.
     discard_sector_alignment: u32,
+    /// The maximum number of write zeroes sectors in one segment.
     max_write_zeroes_sectors: u32,
+    /// The maximum number of segments in a write zeroes command.
     max_write_zeroes_seg: u32,
+    /// Set if a write zeroes command may result in the
+    /// deallocation of one or more of the sectors.
     write_zeros_may_unmap: u8,
     unused1: [u8; 3],
 }
@@ -83,9 +98,13 @@ pub struct VirtioBlockGeometry {
 #[derive(Debug, Copy, Clone, Pod)]
 #[repr(C)]
 pub struct VirtioBlockTopology {
+    /// Exponent for physical block per logical block.
     physical_block_exp: u8,
+    /// Alignment offset in logical blocks.
     alignment_offset: u8,
+    /// Minimum I/O size without performance penalty in logical blocks.
     min_io_size: u16,
+    /// Optimal sustained I/O size in logical blocks.
     opt_io_size: u32,
 }
 
@@ -94,4 +113,20 @@ impl VirtioBlockConfig {
         let memory = transport.device_config_memory();
         SafePtr::new(memory, 0)
     }
+
+    pub(self) const fn sector_size() -> usize {
+        SECTOR_SIZE
+    }
+
+    pub(self) fn block_size(&self) -> usize {
+        self.blk_size as usize
+    }
+
+    pub(self) fn capacity_sectors(&self) -> usize {
+        self.capacity as usize
+    }
+
+    pub(self) fn capacity_bytes(&self) -> usize {
+        self.capacity_sectors() * Self::sector_size()
+    }
 }