1 // SPDX-License-Identifier: GPL-2.0 2 3 //! Generic disk abstraction. 4 //! 5 //! C header: [`include/linux/blkdev.h`](srctree/include/linux/blkdev.h) 6 //! C header: [`include/linux/blk_mq.h`](srctree/include/linux/blk_mq.h) 7 8 use crate::block::mq::{raw_writer::RawWriter, Operations, TagSet}; 9 use crate::error; 10 use crate::{bindings, error::from_err_ptr, error::Result, sync::Arc}; 11 use core::fmt::{self, Write}; 12 13 /// A builder for [`GenDisk`]. 14 /// 15 /// Use this struct to configure and add new [`GenDisk`] to the VFS. 16 pub struct GenDiskBuilder { 17 rotational: bool, 18 logical_block_size: u32, 19 physical_block_size: u32, 20 capacity_sectors: u64, 21 } 22 23 impl Default for GenDiskBuilder { 24 fn default() -> Self { 25 Self { 26 rotational: false, 27 logical_block_size: bindings::PAGE_SIZE as u32, 28 physical_block_size: bindings::PAGE_SIZE as u32, 29 capacity_sectors: 0, 30 } 31 } 32 } 33 34 impl GenDiskBuilder { 35 /// Create a new instance. 36 pub fn new() -> Self { 37 Self::default() 38 } 39 40 /// Set the rotational media attribute for the device to be built. 41 pub fn rotational(mut self, rotational: bool) -> Self { 42 self.rotational = rotational; 43 self 44 } 45 46 /// Validate block size by verifying that it is between 512 and `PAGE_SIZE`, 47 /// and that it is a power of two. 48 fn validate_block_size(size: u32) -> Result<()> { 49 if !(512..=bindings::PAGE_SIZE as u32).contains(&size) || !size.is_power_of_two() { 50 Err(error::code::EINVAL) 51 } else { 52 Ok(()) 53 } 54 } 55 56 /// Set the logical block size of the device to be built. 57 /// 58 /// This method will check that block size is a power of two and between 512 59 /// and 4096. If not, an error is returned and the block size is not set. 60 /// 61 /// This is the smallest unit the storage device can address. It is 62 /// typically 4096 bytes. 63 pub fn logical_block_size(mut self, block_size: u32) -> Result<Self> { 64 Self::validate_block_size(block_size)?; 65 self.logical_block_size = block_size; 66 Ok(self) 67 } 68 69 /// Set the physical block size of the device to be built. 70 /// 71 /// This method will check that block size is a power of two and between 512 72 /// and 4096. If not, an error is returned and the block size is not set. 73 /// 74 /// This is the smallest unit a physical storage device can write 75 /// atomically. It is usually the same as the logical block size but may be 76 /// bigger. One example is SATA drives with 4096 byte physical block size 77 /// that expose a 512 byte logical block size to the operating system. 78 pub fn physical_block_size(mut self, block_size: u32) -> Result<Self> { 79 Self::validate_block_size(block_size)?; 80 self.physical_block_size = block_size; 81 Ok(self) 82 } 83 84 /// Set the capacity of the device to be built, in sectors (512 bytes). 85 pub fn capacity_sectors(mut self, capacity: u64) -> Self { 86 self.capacity_sectors = capacity; 87 self 88 } 89 90 /// Build a new `GenDisk` and add it to the VFS. 91 pub fn build<T: Operations>( 92 self, 93 name: fmt::Arguments<'_>, 94 tagset: Arc<TagSet<T>>, 95 ) -> Result<GenDisk<T>> { 96 let lock_class_key = crate::sync::LockClassKey::new(); 97 98 // SAFETY: `bindings::queue_limits` contain only fields that are valid when zeroed. 99 let mut lim: bindings::queue_limits = unsafe { core::mem::zeroed() }; 100 101 lim.logical_block_size = self.logical_block_size; 102 lim.physical_block_size = self.physical_block_size; 103 104 // SAFETY: `tagset.raw_tag_set()` points to a valid and initialized tag set 105 let gendisk = from_err_ptr(unsafe { 106 bindings::__blk_mq_alloc_disk( 107 tagset.raw_tag_set(), 108 &mut lim, 109 core::ptr::null_mut(), 110 lock_class_key.as_ptr(), 111 ) 112 })?; 113 114 const TABLE: bindings::block_device_operations = bindings::block_device_operations { 115 submit_bio: None, 116 open: None, 117 release: None, 118 ioctl: None, 119 compat_ioctl: None, 120 check_events: None, 121 unlock_native_capacity: None, 122 getgeo: None, 123 set_read_only: None, 124 swap_slot_free_notify: None, 125 report_zones: None, 126 devnode: None, 127 alternative_gpt_sector: None, 128 get_unique_id: None, 129 // TODO: Set to THIS_MODULE. Waiting for const_refs_to_static feature to 130 // be merged (unstable in rustc 1.78 which is staged for linux 6.10) 131 // https://github.com/rust-lang/rust/issues/119618 132 owner: core::ptr::null_mut(), 133 pr_ops: core::ptr::null_mut(), 134 free_disk: None, 135 poll_bio: None, 136 }; 137 138 // SAFETY: `gendisk` is a valid pointer as we initialized it above 139 unsafe { (*gendisk).fops = &TABLE }; 140 141 let mut raw_writer = RawWriter::from_array( 142 // SAFETY: `gendisk` points to a valid and initialized instance. We 143 // have exclusive access, since the disk is not added to the VFS 144 // yet. 145 unsafe { &mut (*gendisk).disk_name }, 146 )?; 147 raw_writer.write_fmt(name)?; 148 raw_writer.write_char('\0')?; 149 150 // SAFETY: `gendisk` points to a valid and initialized instance of 151 // `struct gendisk`. `set_capacity` takes a lock to synchronize this 152 // operation, so we will not race. 153 unsafe { bindings::set_capacity(gendisk, self.capacity_sectors) }; 154 155 if !self.rotational { 156 // SAFETY: `gendisk` points to a valid and initialized instance of 157 // `struct gendisk`. This operation uses a relaxed atomic bit flip 158 // operation, so there is no race on this field. 159 unsafe { bindings::blk_queue_flag_set(bindings::QUEUE_FLAG_NONROT, (*gendisk).queue) }; 160 } else { 161 // SAFETY: `gendisk` points to a valid and initialized instance of 162 // `struct gendisk`. This operation uses a relaxed atomic bit flip 163 // operation, so there is no race on this field. 164 unsafe { 165 bindings::blk_queue_flag_clear(bindings::QUEUE_FLAG_NONROT, (*gendisk).queue) 166 }; 167 } 168 169 crate::error::to_result( 170 // SAFETY: `gendisk` points to a valid and initialized instance of 171 // `struct gendisk`. 172 unsafe { 173 bindings::device_add_disk(core::ptr::null_mut(), gendisk, core::ptr::null_mut()) 174 }, 175 )?; 176 177 // INVARIANT: `gendisk` was initialized above. 178 // INVARIANT: `gendisk` was added to the VFS via `device_add_disk` above. 179 Ok(GenDisk { 180 _tagset: tagset, 181 gendisk, 182 }) 183 } 184 } 185 186 /// A generic block device. 187 /// 188 /// # Invariants 189 /// 190 /// - `gendisk` must always point to an initialized and valid `struct gendisk`. 191 /// - `gendisk` was added to the VFS through a call to 192 /// `bindings::device_add_disk`. 193 pub struct GenDisk<T: Operations> { 194 _tagset: Arc<TagSet<T>>, 195 gendisk: *mut bindings::gendisk, 196 } 197 198 // SAFETY: `GenDisk` is an owned pointer to a `struct gendisk` and an `Arc` to a 199 // `TagSet` It is safe to send this to other threads as long as T is Send. 200 unsafe impl<T: Operations + Send> Send for GenDisk<T> {} 201 202 impl<T: Operations> Drop for GenDisk<T> { 203 fn drop(&mut self) { 204 // SAFETY: By type invariant, `self.gendisk` points to a valid and 205 // initialized instance of `struct gendisk`, and it was previously added 206 // to the VFS. 207 unsafe { bindings::del_gendisk(self.gendisk) }; 208 } 209 } 210