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// SPDX-License-Identifier: GPL-2.0
//! Generic disk abstraction.
//!
//! C header: [`include/linux/blkdev.h`](srctree/include/linux/blkdev.h)
//! C header: [`include/linux/blk_mq.h`](srctree/include/linux/blk_mq.h)
use crate::block::mq::{raw_writer::RawWriter, Operations, TagSet};
use crate::error;
use crate::{bindings, error::from_err_ptr, error::Result, sync::Arc};
use core::fmt::{self, Write};
/// A builder for [`GenDisk`].
///
/// Use this struct to configure and add new [`GenDisk`] to the VFS.
pub struct GenDiskBuilder {
rotational: bool,
logical_block_size: u32,
physical_block_size: u32,
capacity_sectors: u64,
}
impl Default for GenDiskBuilder {
fn default() -> Self {
Self {
rotational: false,
logical_block_size: bindings::PAGE_SIZE as u32,
physical_block_size: bindings::PAGE_SIZE as u32,
capacity_sectors: 0,
}
}
}
impl GenDiskBuilder {
/// Create a new instance.
pub fn new() -> Self {
Self::default()
}
/// Set the rotational media attribute for the device to be built.
pub fn rotational(mut self, rotational: bool) -> Self {
self.rotational = rotational;
self
}
/// Validate block size by verifying that it is between 512 and `PAGE_SIZE`,
/// and that it is a power of two.
fn validate_block_size(size: u32) -> Result<()> {
if !(512..=bindings::PAGE_SIZE as u32).contains(&size) || !size.is_power_of_two() {
Err(error::code::EINVAL)
} else {
Ok(())
}
}
/// Set the logical block size of the device to be built.
///
/// This method will check that block size is a power of two and between 512
/// and 4096. If not, an error is returned and the block size is not set.
///
/// This is the smallest unit the storage device can address. It is
/// typically 4096 bytes.
pub fn logical_block_size(mut self, block_size: u32) -> Result<Self> {
Self::validate_block_size(block_size)?;
self.logical_block_size = block_size;
Ok(self)
}
/// Set the physical block size of the device to be built.
///
/// This method will check that block size is a power of two and between 512
/// and 4096. If not, an error is returned and the block size is not set.
///
/// This is the smallest unit a physical storage device can write
/// atomically. It is usually the same as the logical block size but may be
/// bigger. One example is SATA drives with 4096 byte physical block size
/// that expose a 512 byte logical block size to the operating system.
pub fn physical_block_size(mut self, block_size: u32) -> Result<Self> {
Self::validate_block_size(block_size)?;
self.physical_block_size = block_size;
Ok(self)
}
/// Set the capacity of the device to be built, in sectors (512 bytes).
pub fn capacity_sectors(mut self, capacity: u64) -> Self {
self.capacity_sectors = capacity;
self
}
/// Build a new `GenDisk` and add it to the VFS.
pub fn build<T: Operations>(
self,
name: fmt::Arguments<'_>,
tagset: Arc<TagSet<T>>,
) -> Result<GenDisk<T>> {
let lock_class_key = crate::sync::LockClassKey::new();
// SAFETY: `bindings::queue_limits` contain only fields that are valid when zeroed.
let mut lim: bindings::queue_limits = unsafe { core::mem::zeroed() };
lim.logical_block_size = self.logical_block_size;
lim.physical_block_size = self.physical_block_size;
// SAFETY: `tagset.raw_tag_set()` points to a valid and initialized tag set
let gendisk = from_err_ptr(unsafe {
bindings::__blk_mq_alloc_disk(
tagset.raw_tag_set(),
&mut lim,
core::ptr::null_mut(),
lock_class_key.as_ptr(),
)
})?;
const TABLE: bindings::block_device_operations = bindings::block_device_operations {
submit_bio: None,
open: None,
release: None,
ioctl: None,
compat_ioctl: None,
check_events: None,
unlock_native_capacity: None,
getgeo: None,
set_read_only: None,
swap_slot_free_notify: None,
report_zones: None,
devnode: None,
alternative_gpt_sector: None,
get_unique_id: None,
// TODO: Set to THIS_MODULE. Waiting for const_refs_to_static feature to
// be merged (unstable in rustc 1.78 which is staged for linux 6.10)
// https://github.com/rust-lang/rust/issues/119618
owner: core::ptr::null_mut(),
pr_ops: core::ptr::null_mut(),
free_disk: None,
poll_bio: None,
};
// SAFETY: `gendisk` is a valid pointer as we initialized it above
unsafe { (*gendisk).fops = &TABLE };
let mut raw_writer = RawWriter::from_array(
// SAFETY: `gendisk` points to a valid and initialized instance. We
// have exclusive access, since the disk is not added to the VFS
// yet.
unsafe { &mut (*gendisk).disk_name },
)?;
raw_writer.write_fmt(name)?;
raw_writer.write_char('\0')?;
// SAFETY: `gendisk` points to a valid and initialized instance of
// `struct gendisk`. `set_capacity` takes a lock to synchronize this
// operation, so we will not race.
unsafe { bindings::set_capacity(gendisk, self.capacity_sectors) };
if !self.rotational {
// SAFETY: `gendisk` points to a valid and initialized instance of
// `struct gendisk`. This operation uses a relaxed atomic bit flip
// operation, so there is no race on this field.
unsafe { bindings::blk_queue_flag_set(bindings::QUEUE_FLAG_NONROT, (*gendisk).queue) };
} else {
// SAFETY: `gendisk` points to a valid and initialized instance of
// `struct gendisk`. This operation uses a relaxed atomic bit flip
// operation, so there is no race on this field.
unsafe {
bindings::blk_queue_flag_clear(bindings::QUEUE_FLAG_NONROT, (*gendisk).queue)
};
}
crate::error::to_result(
// SAFETY: `gendisk` points to a valid and initialized instance of
// `struct gendisk`.
unsafe {
bindings::device_add_disk(core::ptr::null_mut(), gendisk, core::ptr::null_mut())
},
)?;
// INVARIANT: `gendisk` was initialized above.
// INVARIANT: `gendisk` was added to the VFS via `device_add_disk` above.
Ok(GenDisk {
_tagset: tagset,
gendisk,
})
}
}
/// A generic block device.
///
/// # Invariants
///
/// - `gendisk` must always point to an initialized and valid `struct gendisk`.
/// - `gendisk` was added to the VFS through a call to
/// `bindings::device_add_disk`.
pub struct GenDisk<T: Operations> {
_tagset: Arc<TagSet<T>>,
gendisk: *mut bindings::gendisk,
}
// SAFETY: `GenDisk` is an owned pointer to a `struct gendisk` and an `Arc` to a
// `TagSet` It is safe to send this to other threads as long as T is Send.
unsafe impl<T: Operations + Send> Send for GenDisk<T> {}
impl<T: Operations> Drop for GenDisk<T> {
fn drop(&mut self) {
// SAFETY: By type invariant, `self.gendisk` points to a valid and
// initialized instance of `struct gendisk`, and it was previously added
// to the VFS.
unsafe { bindings::del_gendisk(self.gendisk) };
}
}
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