Line data Source code
1 : //!
2 : //! Low-level Block-oriented I/O functions
3 : //!
4 :
5 : use super::ephemeral_file::EphemeralFile;
6 : use super::storage_layer::delta_layer::{Adapter, DeltaLayerInner};
7 : use crate::context::RequestContext;
8 : use crate::page_cache::{self, FileId, PageReadGuard, PageWriteGuard, ReadBufResult, PAGE_SZ};
9 : use crate::virtual_file::VirtualFile;
10 : use bytes::Bytes;
11 : use std::ops::Deref;
12 :
13 : /// This is implemented by anything that can read 8 kB (PAGE_SZ)
14 : /// blocks, using the page cache
15 : ///
16 : /// There are currently two implementations: EphemeralFile, and FileBlockReader
17 : /// below.
18 : pub trait BlockReader {
19 : ///
20 : /// Create a new "cursor" for reading from this reader.
21 : ///
22 : /// A cursor caches the last accessed page, allowing for faster
23 : /// access if the same block is accessed repeatedly.
24 : fn block_cursor(&self) -> BlockCursor<'_>;
25 : }
26 :
27 : impl<B> BlockReader for &B
28 : where
29 : B: BlockReader,
30 : {
31 211122 : fn block_cursor(&self) -> BlockCursor<'_> {
32 211122 : (*self).block_cursor()
33 211122 : }
34 : }
35 :
36 : /// Reference to an in-memory copy of an immutable on-disk block.
37 : pub enum BlockLease<'a> {
38 : PageReadGuard(PageReadGuard<'static>),
39 : EphemeralFileMutableTail(&'a [u8; PAGE_SZ]),
40 : #[cfg(test)]
41 : Arc(std::sync::Arc<[u8; PAGE_SZ]>),
42 : #[cfg(test)]
43 : Vec(Vec<u8>),
44 : }
45 :
46 : impl From<PageReadGuard<'static>> for BlockLease<'static> {
47 2739887 : fn from(value: PageReadGuard<'static>) -> BlockLease<'static> {
48 2739887 : BlockLease::PageReadGuard(value)
49 2739887 : }
50 : }
51 :
52 : #[cfg(test)]
53 : impl<'a> From<std::sync::Arc<[u8; PAGE_SZ]>> for BlockLease<'a> {
54 1016718 : fn from(value: std::sync::Arc<[u8; PAGE_SZ]>) -> Self {
55 1016718 : BlockLease::Arc(value)
56 1016718 : }
57 : }
58 :
59 : impl<'a> Deref for BlockLease<'a> {
60 : type Target = [u8; PAGE_SZ];
61 :
62 15852814 : fn deref(&self) -> &Self::Target {
63 15852814 : match self {
64 13498710 : BlockLease::PageReadGuard(v) => v.deref(),
65 1302878 : BlockLease::EphemeralFileMutableTail(v) => v,
66 : #[cfg(test)]
67 1016718 : BlockLease::Arc(v) => v.deref(),
68 : #[cfg(test)]
69 34508 : BlockLease::Vec(v) => {
70 34508 : TryFrom::try_from(&v[..]).expect("caller must ensure that v has PAGE_SZ")
71 : }
72 : }
73 15852814 : }
74 : }
75 :
76 : /// Provides the ability to read blocks from different sources,
77 : /// similar to using traits for this purpose.
78 : ///
79 : /// Unlike traits, we also support the read function to be async though.
80 : pub(crate) enum BlockReaderRef<'a> {
81 : FileBlockReader(&'a FileBlockReader<'a>),
82 : EphemeralFile(&'a EphemeralFile),
83 : Adapter(Adapter<&'a DeltaLayerInner>),
84 : #[cfg(test)]
85 : TestDisk(&'a super::disk_btree::tests::TestDisk),
86 : #[cfg(test)]
87 : VirtualFile(&'a VirtualFile),
88 : }
89 :
90 : impl<'a> BlockReaderRef<'a> {
91 : #[inline(always)]
92 8731616 : async fn read_blk(
93 8731616 : &self,
94 8731616 : blknum: u32,
95 8731616 : ctx: &RequestContext,
96 8731616 : ) -> Result<BlockLease, std::io::Error> {
97 8731616 : use BlockReaderRef::*;
98 8731616 : match self {
99 655799 : FileBlockReader(r) => r.read_blk(blknum, ctx).await,
100 4955897 : EphemeralFile(r) => r.read_blk(blknum, ctx).await,
101 2083002 : Adapter(r) => r.read_blk(blknum, ctx).await,
102 : #[cfg(test)]
103 1016718 : TestDisk(r) => r.read_blk(blknum),
104 : #[cfg(test)]
105 20200 : VirtualFile(r) => r.read_blk(blknum, ctx).await,
106 : }
107 8731616 : }
108 : }
109 :
110 : ///
111 : /// A "cursor" for efficiently reading multiple pages from a BlockReader
112 : ///
113 : /// You can access the last page with `*cursor`. 'read_blk' returns 'self', so
114 : /// that in many cases you can use a BlockCursor as a drop-in replacement for
115 : /// the underlying BlockReader. For example:
116 : ///
117 : /// ```no_run
118 : /// # use pageserver::tenant::block_io::{BlockReader, FileBlockReader};
119 : /// # use pageserver::context::RequestContext;
120 : /// # let reader: FileBlockReader = unimplemented!("stub");
121 : /// # let ctx: RequestContext = unimplemented!("stub");
122 : /// let cursor = reader.block_cursor();
123 : /// let buf = cursor.read_blk(1, &ctx);
124 : /// // do stuff with 'buf'
125 : /// let buf = cursor.read_blk(2, &ctx);
126 : /// // do stuff with 'buf'
127 : /// ```
128 : ///
129 : pub struct BlockCursor<'a> {
130 : reader: BlockReaderRef<'a>,
131 : }
132 :
133 : impl<'a> BlockCursor<'a> {
134 3569561 : pub(crate) fn new(reader: BlockReaderRef<'a>) -> Self {
135 3569561 : BlockCursor { reader }
136 3569561 : }
137 : // Needed by cli
138 0 : pub fn new_fileblockreader(reader: &'a FileBlockReader) -> Self {
139 0 : BlockCursor {
140 0 : reader: BlockReaderRef::FileBlockReader(reader),
141 0 : }
142 0 : }
143 :
144 : /// Read a block.
145 : ///
146 : /// Returns a "lease" object that can be used to
147 : /// access to the contents of the page. (For the page cache, the
148 : /// lease object represents a lock on the buffer.)
149 : #[inline(always)]
150 8731616 : pub async fn read_blk(
151 8731616 : &self,
152 8731616 : blknum: u32,
153 8731616 : ctx: &RequestContext,
154 8731616 : ) -> Result<BlockLease, std::io::Error> {
155 8731616 : self.reader.read_blk(blknum, ctx).await
156 8731616 : }
157 : }
158 :
159 : /// An adapter for reading a (virtual) file using the page cache.
160 : ///
161 : /// The file is assumed to be immutable. This doesn't provide any functions
162 : /// for modifying the file, nor for invalidating the cache if it is modified.
163 : pub struct FileBlockReader<'a> {
164 : pub file: &'a VirtualFile,
165 :
166 : /// Unique ID of this file, used as key in the page cache.
167 : file_id: page_cache::FileId,
168 : }
169 :
170 : impl<'a> FileBlockReader<'a> {
171 2296090 : pub fn new(file: &'a VirtualFile, file_id: FileId) -> Self {
172 2296090 : FileBlockReader { file_id, file }
173 2296090 : }
174 :
175 : /// Read a page from the underlying file into given buffer.
176 60076 : async fn fill_buffer(
177 60076 : &self,
178 60076 : buf: PageWriteGuard<'static>,
179 60076 : blkno: u32,
180 60076 : ctx: &RequestContext,
181 60076 : ) -> Result<PageWriteGuard<'static>, std::io::Error> {
182 60076 : assert!(buf.len() == PAGE_SZ);
183 60076 : self.file
184 60076 : .read_exact_at_page(buf, blkno as u64 * PAGE_SZ as u64, ctx)
185 36563 : .await
186 60076 : }
187 : /// Read a block.
188 : ///
189 : /// Returns a "lease" object that can be used to
190 : /// access to the contents of the page. (For the page cache, the
191 : /// lease object represents a lock on the buffer.)
192 2739887 : pub async fn read_blk<'b>(
193 2739887 : &self,
194 2739887 : blknum: u32,
195 2739887 : ctx: &RequestContext,
196 2739887 : ) -> Result<BlockLease<'b>, std::io::Error> {
197 2739887 : let cache = page_cache::get();
198 2739887 : match cache
199 2739887 : .read_immutable_buf(self.file_id, blknum, ctx)
200 34001 : .await
201 2739887 : .map_err(|e| {
202 0 : std::io::Error::new(
203 0 : std::io::ErrorKind::Other,
204 0 : format!("Failed to read immutable buf: {e:#}"),
205 0 : )
206 2739887 : })? {
207 2679811 : ReadBufResult::Found(guard) => Ok(guard.into()),
208 60076 : ReadBufResult::NotFound(write_guard) => {
209 : // Read the page from disk into the buffer
210 60076 : let write_guard = self.fill_buffer(write_guard, blknum, ctx).await?;
211 60076 : Ok(write_guard.mark_valid().into())
212 : }
213 : }
214 2739887 : }
215 : }
216 :
217 : impl BlockReader for FileBlockReader<'_> {
218 487050 : fn block_cursor(&self) -> BlockCursor<'_> {
219 487050 : BlockCursor::new(BlockReaderRef::FileBlockReader(self))
220 487050 : }
221 : }
222 :
223 : ///
224 : /// Trait for block-oriented output
225 : ///
226 : pub trait BlockWriter {
227 : ///
228 : /// Write a page to the underlying storage.
229 : ///
230 : /// 'buf' must be of size PAGE_SZ. Returns the block number the page was
231 : /// written to.
232 : ///
233 : fn write_blk(&mut self, buf: Bytes) -> Result<u32, std::io::Error>;
234 : }
235 :
236 : ///
237 : /// A simple in-memory buffer of blocks.
238 : ///
239 : pub struct BlockBuf {
240 : pub blocks: Vec<Bytes>,
241 : }
242 : impl BlockWriter for BlockBuf {
243 14223 : fn write_blk(&mut self, buf: Bytes) -> Result<u32, std::io::Error> {
244 14223 : assert!(buf.len() == PAGE_SZ);
245 14223 : let blknum = self.blocks.len();
246 14223 : self.blocks.push(buf);
247 14223 : Ok(blknum as u32)
248 14223 : }
249 : }
250 :
251 : impl BlockBuf {
252 1564 : pub fn new() -> Self {
253 1564 : BlockBuf { blocks: Vec::new() }
254 1564 : }
255 :
256 2023972 : pub fn size(&self) -> u64 {
257 2023972 : (self.blocks.len() * PAGE_SZ) as u64
258 2023972 : }
259 : }
260 : impl Default for BlockBuf {
261 0 : fn default() -> Self {
262 0 : Self::new()
263 0 : }
264 : }
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