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::{bindings, error::from_err_ptr, error::Result, sync::Arc}; 10 use crate::{error, static_lock_class}; 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 // SAFETY: `bindings::queue_limits` contain only fields that are valid when zeroed. 97 let mut lim: bindings::queue_limits = unsafe { core::mem::zeroed() }; 98 99 lim.logical_block_size = self.logical_block_size; 100 lim.physical_block_size = self.physical_block_size; 101 if self.rotational { 102 lim.features = bindings::BLK_FEAT_ROTATIONAL; 103 } 104 105 // SAFETY: `tagset.raw_tag_set()` points to a valid and initialized tag set 106 let gendisk = from_err_ptr(unsafe { 107 bindings::__blk_mq_alloc_disk( 108 tagset.raw_tag_set(), 109 &mut lim, 110 core::ptr::null_mut(), 111 static_lock_class!().as_ptr(), 112 ) 113 })?; 114 115 const TABLE: bindings::block_device_operations = bindings::block_device_operations { 116 submit_bio: None, 117 open: None, 118 release: None, 119 ioctl: None, 120 compat_ioctl: None, 121 check_events: None, 122 unlock_native_capacity: None, 123 getgeo: None, 124 set_read_only: None, 125 swap_slot_free_notify: None, 126 report_zones: None, 127 devnode: None, 128 alternative_gpt_sector: None, 129 get_unique_id: None, 130 // TODO: Set to THIS_MODULE. Waiting for const_refs_to_static feature to 131 // be merged (unstable in rustc 1.78 which is staged for linux 6.10) 132 // https://github.com/rust-lang/rust/issues/119618 133 owner: core::ptr::null_mut(), 134 pr_ops: core::ptr::null_mut(), 135 free_disk: None, 136 poll_bio: None, 137 }; 138 139 // SAFETY: `gendisk` is a valid pointer as we initialized it above 140 unsafe { (*gendisk).fops = &TABLE }; 141 142 let mut raw_writer = RawWriter::from_array( 143 // SAFETY: `gendisk` points to a valid and initialized instance. We 144 // have exclusive access, since the disk is not added to the VFS 145 // yet. 146 unsafe { &mut (*gendisk).disk_name }, 147 )?; 148 raw_writer.write_fmt(name)?; 149 raw_writer.write_char('\0')?; 150 151 // SAFETY: `gendisk` points to a valid and initialized instance of 152 // `struct gendisk`. `set_capacity` takes a lock to synchronize this 153 // operation, so we will not race. 154 unsafe { bindings::set_capacity(gendisk, self.capacity_sectors) }; 155 156 crate::error::to_result( 157 // SAFETY: `gendisk` points to a valid and initialized instance of 158 // `struct gendisk`. 159 unsafe { 160 bindings::device_add_disk(core::ptr::null_mut(), gendisk, core::ptr::null_mut()) 161 }, 162 )?; 163 164 // INVARIANT: `gendisk` was initialized above. 165 // INVARIANT: `gendisk` was added to the VFS via `device_add_disk` above. 166 Ok(GenDisk { 167 _tagset: tagset, 168 gendisk, 169 }) 170 } 171 } 172 173 /// A generic block device. 174 /// 175 /// # Invariants 176 /// 177 /// - `gendisk` must always point to an initialized and valid `struct gendisk`. 178 /// - `gendisk` was added to the VFS through a call to 179 /// `bindings::device_add_disk`. 180 pub struct GenDisk<T: Operations> { 181 _tagset: Arc<TagSet<T>>, 182 gendisk: *mut bindings::gendisk, 183 } 184 185 // SAFETY: `GenDisk` is an owned pointer to a `struct gendisk` and an `Arc` to a 186 // `TagSet` It is safe to send this to other threads as long as T is Send. 187 unsafe impl<T: Operations + Send> Send for GenDisk<T> {} 188 189 impl<T: Operations> Drop for GenDisk<T> { 190 fn drop(&mut self) { 191 // SAFETY: By type invariant, `self.gendisk` points to a valid and 192 // initialized instance of `struct gendisk`, and it was previously added 193 // to the VFS. 194 unsafe { bindings::del_gendisk(self.gendisk) }; 195 } 196 } 197