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Linux/rust/kernel/block/mq.rs

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Diff markup

Differences between /rust/kernel/block/mq.rs (Architecture mips) and /rust/kernel/block/mq.rs (Architecture sparc)


  1 // SPDX-License-Identifier: GPL-2.0                 1 // SPDX-License-Identifier: GPL-2.0
  2                                                     2 
  3 //! This module provides types for implementin      3 //! This module provides types for implementing block drivers that interface the
  4 //! blk-mq subsystem.                               4 //! blk-mq subsystem.
  5 //!                                                 5 //!
  6 //! To implement a block device driver, a Rust      6 //! To implement a block device driver, a Rust module must do the following:
  7 //!                                                 7 //!
  8 //! - Implement [`Operations`] for a type `T`.      8 //! - Implement [`Operations`] for a type `T`.
  9 //! - Create a [`TagSet<T>`].                       9 //! - Create a [`TagSet<T>`].
 10 //! - Create a [`GenDisk<T>`], via the [`GenDi     10 //! - Create a [`GenDisk<T>`], via the [`GenDiskBuilder`].
 11 //! - Add the disk to the system by calling [`     11 //! - Add the disk to the system by calling [`GenDiskBuilder::build`] passing in
 12 //!   the `TagSet` reference.                      12 //!   the `TagSet` reference.
 13 //!                                                13 //!
 14 //! The types available in this module that ha     14 //! The types available in this module that have direct C counterparts are:
 15 //!                                                15 //!
 16 //! - The [`TagSet`] type that abstracts the C     16 //! - The [`TagSet`] type that abstracts the C type `struct tag_set`.
 17 //! - The [`GenDisk`] type that abstracts the      17 //! - The [`GenDisk`] type that abstracts the C type `struct gendisk`.
 18 //! - The [`Request`] type that abstracts the      18 //! - The [`Request`] type that abstracts the C type `struct request`.
 19 //!                                                19 //!
 20 //! The kernel will interface with the block d     20 //! The kernel will interface with the block device driver by calling the method
 21 //! implementations of the `Operations` trait.     21 //! implementations of the `Operations` trait.
 22 //!                                                22 //!
 23 //! IO requests are passed to the driver as [`     23 //! IO requests are passed to the driver as [`kernel::types::ARef<Request>`]
 24 //! instances. The `Request` type is a wrapper     24 //! instances. The `Request` type is a wrapper around the C `struct request`.
 25 //! The driver must mark end of processing by      25 //! The driver must mark end of processing by calling one of the
 26 //! `Request::end`, methods. Failure to do so      26 //! `Request::end`, methods. Failure to do so can lead to deadlock or timeout
 27 //! errors. Please note that the C function `b     27 //! errors. Please note that the C function `blk_mq_start_request` is implicitly
 28 //! called when the request is queued with the     28 //! called when the request is queued with the driver.
 29 //!                                                29 //!
 30 //! The `TagSet` is responsible for creating a     30 //! The `TagSet` is responsible for creating and maintaining a mapping between
 31 //! `Request`s and integer ids as well as carr     31 //! `Request`s and integer ids as well as carrying a pointer to the vtable
 32 //! generated by `Operations`. This mapping is     32 //! generated by `Operations`. This mapping is useful for associating
 33 //! completions from hardware with the correct     33 //! completions from hardware with the correct `Request` instance. The `TagSet`
 34 //! determines the maximum queue depth by sett     34 //! determines the maximum queue depth by setting the number of `Request`
 35 //! instances available to the driver, and it      35 //! instances available to the driver, and it determines the number of queues to
 36 //! instantiate for the driver. If possible, a     36 //! instantiate for the driver. If possible, a driver should allocate one queue
 37 //! per core, to keep queue data local to a co     37 //! per core, to keep queue data local to a core.
 38 //!                                                38 //!
 39 //! One `TagSet` instance can be shared betwee     39 //! One `TagSet` instance can be shared between multiple `GenDisk` instances.
 40 //! This can be useful when implementing drive     40 //! This can be useful when implementing drivers where one piece of hardware
 41 //! with one set of IO resources are represent     41 //! with one set of IO resources are represented to the user as multiple disks.
 42 //!                                                42 //!
 43 //! One significant difference between block d     43 //! One significant difference between block device drivers implemented with
 44 //! these Rust abstractions and drivers implem     44 //! these Rust abstractions and drivers implemented in C, is that the Rust
 45 //! drivers have to own a reference count on t     45 //! drivers have to own a reference count on the `Request` type when the IO is
 46 //! in flight. This is to ensure that the C `s     46 //! in flight. This is to ensure that the C `struct request` instances backing
 47 //! the Rust `Request` instances are live whil     47 //! the Rust `Request` instances are live while the Rust driver holds a
 48 //! reference to the `Request`. In addition, t     48 //! reference to the `Request`. In addition, the conversion of an integer tag to
 49 //! a `Request` via the `TagSet` would not be      49 //! a `Request` via the `TagSet` would not be sound without this bookkeeping.
 50 //!                                                50 //!
 51 //! [`GenDisk`]: gen_disk::GenDisk                 51 //! [`GenDisk`]: gen_disk::GenDisk
 52 //! [`GenDisk<T>`]: gen_disk::GenDisk              52 //! [`GenDisk<T>`]: gen_disk::GenDisk
 53 //! [`GenDiskBuilder`]: gen_disk::GenDiskBuild     53 //! [`GenDiskBuilder`]: gen_disk::GenDiskBuilder
 54 //! [`GenDiskBuilder::build`]: gen_disk::GenDi     54 //! [`GenDiskBuilder::build`]: gen_disk::GenDiskBuilder::build
 55 //!                                                55 //!
 56 //! # Example                                      56 //! # Example
 57 //!                                                57 //!
 58 //! ```rust                                        58 //! ```rust
 59 //! use kernel::{                                  59 //! use kernel::{
 60 //!     alloc::flags,                              60 //!     alloc::flags,
 61 //!     block::mq::*,                              61 //!     block::mq::*,
 62 //!     new_mutex,                                 62 //!     new_mutex,
 63 //!     prelude::*,                                63 //!     prelude::*,
 64 //!     sync::{Arc, Mutex},                        64 //!     sync::{Arc, Mutex},
 65 //!     types::{ARef, ForeignOwnable},             65 //!     types::{ARef, ForeignOwnable},
 66 //! };                                             66 //! };
 67 //!                                                67 //!
 68 //! struct MyBlkDevice;                            68 //! struct MyBlkDevice;
 69 //!                                                69 //!
 70 //! #[vtable]                                      70 //! #[vtable]
 71 //! impl Operations for MyBlkDevice {              71 //! impl Operations for MyBlkDevice {
 72 //!                                                72 //!
 73 //!     fn queue_rq(rq: ARef<Request<Self>>, _     73 //!     fn queue_rq(rq: ARef<Request<Self>>, _is_last: bool) -> Result {
 74 //!         Request::end_ok(rq);                   74 //!         Request::end_ok(rq);
 75 //!         Ok(())                                 75 //!         Ok(())
 76 //!     }                                          76 //!     }
 77 //!                                                77 //!
 78 //!     fn commit_rqs() {}                         78 //!     fn commit_rqs() {}
 79 //! }                                              79 //! }
 80 //!                                                80 //!
 81 //! let tagset: Arc<TagSet<MyBlkDevice>> =         81 //! let tagset: Arc<TagSet<MyBlkDevice>> =
 82 //!     Arc::pin_init(TagSet::new(1, 256, 1),      82 //!     Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?;
 83 //! let mut disk = gen_disk::GenDiskBuilder::n     83 //! let mut disk = gen_disk::GenDiskBuilder::new()
 84 //!     .capacity_sectors(4096)                    84 //!     .capacity_sectors(4096)
 85 //!     .build(format_args!("myblk"), tagset)?     85 //!     .build(format_args!("myblk"), tagset)?;
 86 //!                                                86 //!
 87 //! # Ok::<(), kernel::error::Error>(())           87 //! # Ok::<(), kernel::error::Error>(())
 88 //! ```                                            88 //! ```
 89                                                    89 
 90 pub mod gen_disk;                                  90 pub mod gen_disk;
 91 mod operations;                                    91 mod operations;
 92 mod raw_writer;                                    92 mod raw_writer;
 93 mod request;                                       93 mod request;
 94 mod tag_set;                                       94 mod tag_set;
 95                                                    95 
 96 pub use operations::Operations;                    96 pub use operations::Operations;
 97 pub use request::Request;                          97 pub use request::Request;
 98 pub use tag_set::TagSet;                           98 pub use tag_set::TagSet;
                                                      

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