tag_set.rs

 1// SPDX-License-Identifier: GPL-2.0
 2
 3//! This module provides the `TagSet` struct to wrap the C `struct blk_mq_tag_set`.
 4//!
 5//! C header: [`include/linux/blk-mq.h`](srctree/include/linux/blk-mq.h)
 6
 7use core::pin::Pin;
 8
 9use crate::{
10    bindings,
11    block::mq::{operations::OperationsVTable, request::RequestDataWrapper, Operations},
12    error::{self, Result},
13    prelude::try_pin_init,
14    types::Opaque,
15};
16use core::{convert::TryInto, marker::PhantomData};
17use pin_init::{pin_data, pinned_drop, PinInit};
18
19/// A wrapper for the C `struct blk_mq_tag_set`.
20///
21/// `struct blk_mq_tag_set` contains a `struct list_head` and so must be pinned.
22///
23/// # Invariants
24///
25/// - `inner` is initialized and valid.
26#[pin_data(PinnedDrop)]
27#[repr(transparent)]
28pub struct TagSet<T: Operations> {
29    #[pin]
30    inner: Opaque<bindings::blk_mq_tag_set>,
31    _p: PhantomData<T>,
32}
33
34impl<T: Operations> TagSet<T> {
35    /// Try to create a new tag set
36    pub fn new(
37        nr_hw_queues: u32,
38        num_tags: u32,
39        num_maps: u32,
40    ) -> impl PinInit<Self, error::Error> {
41        // SAFETY: `blk_mq_tag_set` only contains integers and pointers, which
42        // all are allowed to be 0.
43        let tag_set: bindings::blk_mq_tag_set = unsafe { core::mem::zeroed() };
44        let tag_set: Result<_> = core::mem::size_of::<RequestDataWrapper>()
45            .try_into()
46            .map(|cmd_size| {
47                bindings::blk_mq_tag_set {
48                    ops: OperationsVTable::<T>::build(),
49                    nr_hw_queues,
50                    timeout: 0, // 0 means default which is 30Hz in C
51                    numa_node: bindings::NUMA_NO_NODE,
52                    queue_depth: num_tags,
53                    cmd_size,
54                    flags: 0,
55                    driver_data: core::ptr::null_mut::<crate::ffi::c_void>(),
56                    nr_maps: num_maps,
57                    ..tag_set
58                }
59            })
60            .map(Opaque::new)
61            .map_err(|e| e.into());
62
63        try_pin_init!(TagSet {
64            inner <- tag_set.pin_chain(|tag_set| {
65                // SAFETY: we do not move out of `tag_set`.
66                let tag_set: &mut Opaque<_> = unsafe { Pin::get_unchecked_mut(tag_set) };
67                // SAFETY: `tag_set` is a reference to an initialized `blk_mq_tag_set`.
68                error::to_result( unsafe { bindings::blk_mq_alloc_tag_set(tag_set.get())})
69            }),
70            _p: PhantomData,
71        })
72    }
73
74    /// Return the pointer to the wrapped `struct blk_mq_tag_set`
75    pub(crate) fn raw_tag_set(&self) -> *mut bindings::blk_mq_tag_set {
76        self.inner.get()
77    }
78}
79
80#[pinned_drop]
81impl<T: Operations> PinnedDrop for TagSet<T> {
82    fn drop(self: Pin<&mut Self>) {
83        // SAFETY: By type invariant `inner` is valid and has been properly
84        // initialized during construction.
85        unsafe { bindings::blk_mq_free_tag_set(self.inner.get()) };
86    }
87}