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Add AioCb::from_boxed_slice
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The existing AioCb constructors work for simple programs where
everything is stored on the stack.  But in more complicated programs the
borrow checker can't prove that a buffer will outlive the AioCb that
references it.  Fix this problem by introducting
AioCb::from_boxed_slice, which takes a reference-counted buffer.

Fixes nix-rust#575
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@asomers
asomers committed Apr 15, 2017
1 parent 635c871 commit f175ea7
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Showing 3 changed files with 105 additions and 34 deletions.
2 changes: 2 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
## [Unreleased]

### Added
- Added `AioCb::from_boxed_slice`
([#582](https://github.com/nix-rust/nix/pull/582)
- Added `nix::unistd::{openat, fstatat, readlink, readlinkat}`
([#551](https://github.com/nix-rust/nix/pull/551))

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57 changes: 49 additions & 8 deletions src/sys/aio.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ use std::io::Write;
use std::io::stderr;
use std::marker::PhantomData;
use std::mem;
use std::rc::Rc;
use std::ptr::{null, null_mut};
use sys::signal::*;
use sys::time::TimeSpec;
Expand Down Expand Up @@ -61,6 +62,17 @@ pub enum AioCancelStat {
AioAllDone = libc::AIO_ALLDONE,
}

/// Private type used by nix to keep buffers from Drop'ing while the kernel has
/// a pointer to them.
#[derive(Clone, Debug)]
enum Keeper<'a> {
none,
/// Keeps a reference to a Boxed slice
boxed(Rc<Box<[u8]>>),
/// Keeps a reference to a slice
phantom(PhantomData<&'a mut [u8]>)
}

/// The basic structure used by all aio functions. Each `aiocb` represents one
/// I/O request.
pub struct AioCb<'a> {
Expand All @@ -69,7 +81,8 @@ pub struct AioCb<'a> {
mutable: bool,
/// Could this `AioCb` potentially have any in-kernel state?
in_progress: bool,
phantom: PhantomData<&'a mut [u8]>
/// Used to keep buffers from Drop'ing
keeper: Keeper<'a>
}

impl<'a> AioCb<'a> {
Expand All @@ -89,7 +102,7 @@ impl<'a> AioCb<'a> {
a.aio_buf = null_mut();

let aiocb = AioCb { aiocb: a, mutable: false, in_progress: false,
phantom: PhantomData};
keeper: Keeper::none};
aiocb
}

Expand All @@ -106,17 +119,43 @@ impl<'a> AioCb<'a> {
/// which operation to use for this individual aiocb
pub fn from_mut_slice(fd: RawFd, offs: off_t, buf: &'a mut [u8],
prio: ::c_int, sigev_notify: SigevNotify,
opcode: LioOpcode) -> AioCb {
opcode: LioOpcode) -> AioCb<'a> {
let mut a = AioCb::common_init(fd, prio, sigev_notify);
a.aio_offset = offs;
a.aio_nbytes = buf.len() as size_t;
// casting an immutable buffer to a mutable pointer looks unsafe, but
// technically its only unsafe to dereference it, not to create it.
a.aio_buf = buf.as_ptr() as *mut c_void;
a.aio_lio_opcode = opcode as ::c_int;

let aiocb = AioCb { aiocb: a, mutable: true, in_progress: false,
phantom: PhantomData};
keeper: Keeper::phantom(PhantomData)};
aiocb
}

/// Constructs a new `AioCb`.
///
/// Unlike `from_mut_slice`, this method returns a structure suitable for
/// placement on the heap.
///
/// * `fd` File descriptor. Required for all aio functions.
/// * `offs` File offset
/// * `buf` A shared memory buffer on the heap
/// * `prio` If POSIX Prioritized IO is supported, then the operation will
/// be prioritized at the process's priority level minus `prio`
/// * `sigev_notify` Determines how you will be notified of event
/// completion.
/// * `opcode` This field is only used for `lio_listio`. It determines
/// which operation to use for this individual aiocb
pub fn from_boxed_slice(fd: RawFd, offs: off_t, buf: Rc<Box<[u8]>>,
prio: ::c_int, sigev_notify: SigevNotify,
opcode: LioOpcode) -> AioCb<'a> {
let mut a = AioCb::common_init(fd, prio, sigev_notify);
a.aio_offset = offs;
a.aio_nbytes = buf.len() as size_t;
a.aio_buf = buf.as_ptr() as *mut c_void;
a.aio_lio_opcode = opcode as ::c_int;

let aiocb = AioCb{ aiocb: a, mutable: true, in_progress: false,
keeper: Keeper::boxed(buf)};
aiocb
}

Expand All @@ -139,12 +178,15 @@ impl<'a> AioCb<'a> {
let mut a = AioCb::common_init(fd, prio, sigev_notify);
a.aio_offset = offs;
a.aio_nbytes = buf.len() as size_t;
// casting an immutable buffer to a mutable pointer looks unsafe,
// but technically its only unsafe to dereference it, not to create
// it.
a.aio_buf = buf.as_ptr() as *mut c_void;
assert!(opcode != LioOpcode::LIO_READ, "Can't read into an immutable buffer");
a.aio_lio_opcode = opcode as ::c_int;

let aiocb = AioCb { aiocb: a, mutable: false, in_progress: false,
phantom: PhantomData};
keeper: Keeper::none};
aiocb
}

Expand Down Expand Up @@ -284,7 +326,6 @@ impl<'a> Debug for AioCb<'a> {
.field("aio_sigevent", &SigEvent::from(&self.aiocb.aio_sigevent))
.field("mutable", &self.mutable)
.field("in_progress", &self.in_progress)
.field("phantom", &self.phantom)
.finish()
}
}
Expand Down
80 changes: 54 additions & 26 deletions test/sys/test_aio.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,9 @@ use nix::sys::aio::*;
use nix::sys::signal::*;
use nix::sys::time::{TimeSpec, TimeValLike};
use std::io::{Write, Read, Seek, SeekFrom};
use std::ops::Deref;
use std::os::unix::io::AsRawFd;
use std::rc::Rc;
use std::{thread, time};
use tempfile::tempfile;

Expand All @@ -23,12 +25,12 @@ fn poll_aio(mut aiocb: &mut AioCb) -> Result<()> {
// AioCancelStat value.
#[test]
fn test_cancel() {
let mut wbuf = "CDEF".to_string().into_bytes();
let wbuf: &'static [u8] = b"CDEF";

let f = tempfile().unwrap();
let mut aiocb = AioCb::from_mut_slice( f.as_raw_fd(),
let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
0, //offset
&mut wbuf,
&wbuf,
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_NOP);
Expand All @@ -47,12 +49,12 @@ fn test_cancel() {
// Tests using aio_cancel_all for all outstanding IOs.
#[test]
fn test_aio_cancel_all() {
let mut wbuf = "CDEF".to_string().into_bytes();
let wbuf: &'static [u8] = b"CDEF";

let f = tempfile().unwrap();
let mut aiocb = AioCb::from_mut_slice( f.as_raw_fd(),
let mut aiocb = AioCb::from_slice(f.as_raw_fd(),
0, //offset
&mut wbuf,
&wbuf,
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_NOP);
Expand Down Expand Up @@ -88,7 +90,7 @@ fn test_aio_suspend() {
const INITIAL: &'static [u8] = b"abcdef123456";
const WBUF: &'static [u8] = b"CDEF";
let timeout = TimeSpec::seconds(10);
let mut rbuf = vec![0; 4];
let rbuf = Rc::new(vec![0; 4].into_boxed_slice());
let mut f = tempfile().unwrap();
f.write(INITIAL).unwrap();

Expand All @@ -99,9 +101,9 @@ fn test_aio_suspend() {
SigevNotify::SigevNone,
LioOpcode::LIO_WRITE);

let mut rcb = AioCb::from_mut_slice( f.as_raw_fd(),
let mut rcb = AioCb::from_boxed_slice( f.as_raw_fd(),
8, //offset
&mut rbuf,
rbuf.clone(),
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_READ);
Expand All @@ -126,6 +128,31 @@ fn test_aio_suspend() {
// for completion
#[test]
fn test_read() {
const INITIAL: &'static [u8] = b"abcdef123456";
let rbuf = Rc::new(vec![0; 4].into_boxed_slice());
const EXPECT: &'static [u8] = b"cdef";
let mut f = tempfile().unwrap();
f.write(INITIAL).unwrap();
{
let mut aiocb = AioCb::from_boxed_slice( f.as_raw_fd(),
2, //offset
rbuf.clone(),
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_NOP);
aiocb.read().unwrap();

let err = poll_aio(&mut aiocb);
assert!(err == Ok(()));
assert!(aiocb.aio_return().unwrap() as usize == EXPECT.len());
}

assert!(EXPECT == rbuf.deref().deref());
}

// Tests from_mut_slice
#[test]
fn test_read_into_mut_slice() {
const INITIAL: &'static [u8] = b"abcdef123456";
let mut rbuf = vec![0; 4];
const EXPECT: &'static [u8] = b"cdef";
Expand All @@ -152,7 +179,7 @@ fn test_read() {
#[test]
#[should_panic(expected = "Can't read into an immutable buffer")]
fn test_read_immutable_buffer() {
let rbuf = vec![0; 4];
let rbuf: &'static [u8] = b"CDEF";
let f = tempfile().unwrap();
let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
2, //offset
Expand All @@ -163,28 +190,29 @@ fn test_read_immutable_buffer() {
aiocb.read().unwrap();
}


// Test a simple aio operation with no completion notification. We must poll
// for completion. Unlike test_aio_read, this test uses AioCb::from_slice
#[test]
fn test_write() {
const INITIAL: &'static [u8] = b"abcdef123456";
const WBUF: &'static [u8] = b"CDEF"; //"CDEF".to_string().into_bytes();
let wbuf = "CDEF".to_string().into_bytes();
let mut rbuf = Vec::new();
const EXPECT: &'static [u8] = b"abCDEF123456";

let mut f = tempfile().unwrap();
f.write(INITIAL).unwrap();
let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
2, //offset
&WBUF,
&wbuf,
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_NOP);
aiocb.write().unwrap();

let err = poll_aio(&mut aiocb);
assert!(err == Ok(()));
assert!(aiocb.aio_return().unwrap() as usize == WBUF.len());
assert!(aiocb.aio_return().unwrap() as usize == wbuf.len());

f.seek(SeekFrom::Start(0)).unwrap();
let len = f.read_to_end(&mut rbuf).unwrap();
Expand Down Expand Up @@ -245,7 +273,7 @@ fn test_write_sigev_signal() {
fn test_lio_listio_wait() {
const INITIAL: &'static [u8] = b"abcdef123456";
const WBUF: &'static [u8] = b"CDEF";
let mut rbuf = vec![0; 4];
let rbuf = Rc::new(vec![0; 4].into_boxed_slice());
let mut rbuf2 = Vec::new();
const EXPECT: &'static [u8] = b"abCDEF123456";
let mut f = tempfile().unwrap();
Expand All @@ -260,9 +288,9 @@ fn test_lio_listio_wait() {
SigevNotify::SigevNone,
LioOpcode::LIO_WRITE);

let mut rcb = AioCb::from_mut_slice( f.as_raw_fd(),
let mut rcb = AioCb::from_boxed_slice( f.as_raw_fd(),
8, //offset
&mut rbuf,
rbuf.clone(),
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_READ);
Expand All @@ -272,7 +300,7 @@ fn test_lio_listio_wait() {
assert!(wcb.aio_return().unwrap() as usize == WBUF.len());
assert!(rcb.aio_return().unwrap() as usize == WBUF.len());
}
assert!(rbuf == b"3456");
assert!(rbuf.deref().deref() == b"3456");

f.seek(SeekFrom::Start(0)).unwrap();
let len = f.read_to_end(&mut rbuf2).unwrap();
Expand All @@ -287,7 +315,7 @@ fn test_lio_listio_wait() {
fn test_lio_listio_nowait() {
const INITIAL: &'static [u8] = b"abcdef123456";
const WBUF: &'static [u8] = b"CDEF";
let mut rbuf = vec![0; 4];
let rbuf = Rc::new(vec![0; 4].into_boxed_slice());
let mut rbuf2 = Vec::new();
const EXPECT: &'static [u8] = b"abCDEF123456";
let mut f = tempfile().unwrap();
Expand All @@ -302,9 +330,9 @@ fn test_lio_listio_nowait() {
SigevNotify::SigevNone,
LioOpcode::LIO_WRITE);

let mut rcb = AioCb::from_mut_slice( f.as_raw_fd(),
let mut rcb = AioCb::from_boxed_slice( f.as_raw_fd(),
8, //offset
&mut rbuf,
rbuf.clone(),
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_READ);
Expand All @@ -316,7 +344,7 @@ fn test_lio_listio_nowait() {
assert!(wcb.aio_return().unwrap() as usize == WBUF.len());
assert!(rcb.aio_return().unwrap() as usize == WBUF.len());
}
assert!(rbuf == b"3456");
assert!(rbuf.deref().deref() == b"3456");

f.seek(SeekFrom::Start(0)).unwrap();
let len = f.read_to_end(&mut rbuf2).unwrap();
Expand All @@ -331,7 +359,7 @@ fn test_lio_listio_nowait() {
fn test_lio_listio_signal() {
const INITIAL: &'static [u8] = b"abcdef123456";
const WBUF: &'static [u8] = b"CDEF";
let mut rbuf = vec![0; 4];
let rbuf = Rc::new(vec![0; 4].into_boxed_slice());
let mut rbuf2 = Vec::new();
const EXPECT: &'static [u8] = b"abCDEF123456";
let mut f = tempfile().unwrap();
Expand All @@ -351,9 +379,9 @@ fn test_lio_listio_signal() {
SigevNotify::SigevNone,
LioOpcode::LIO_WRITE);

let mut rcb = AioCb::from_mut_slice( f.as_raw_fd(),
let mut rcb = AioCb::from_boxed_slice( f.as_raw_fd(),
8, //offset
&mut rbuf,
rbuf.clone(),
0, //priority
SigevNotify::SigevNone,
LioOpcode::LIO_READ);
Expand All @@ -368,7 +396,7 @@ fn test_lio_listio_signal() {
assert!(wcb.aio_return().unwrap() as usize == WBUF.len());
assert!(rcb.aio_return().unwrap() as usize == WBUF.len());
}
assert!(rbuf == b"3456");
assert!(rbuf.deref().deref() == b"3456");

f.seek(SeekFrom::Start(0)).unwrap();
let len = f.read_to_end(&mut rbuf2).unwrap();
Expand All @@ -381,7 +409,7 @@ fn test_lio_listio_signal() {
#[cfg(not(any(target_os = "ios", target_os = "macos")))]
#[should_panic(expected = "Can't read into an immutable buffer")]
fn test_lio_listio_read_immutable() {
let rbuf = vec![0; 4];
let rbuf: &'static [u8] = b"abcd";
let f = tempfile().unwrap();


Expand Down

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