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sys_util: add write_zeroes_all() function

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In the same spirit as write_all() for the standard io::Write::write()
function, add a write_zeroes_all() function with a default
implementation that calls write_zeroes() in a loop until the requested
length is met.  This will allow write_zeroes implementations that don't
necessarily fulfill the entire requested length.

BUG=None
TEST=cargo test -p sys_util write_zeroes

Change-Id: I0fc3a4b3fe8904946e253ab8a2687555b12657be
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1811466
Reviewed-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Cody Schuffelen <schuffelen@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This commit is contained in:
Daniel Verkamp 2019-09-18 11:22:07 -07:00 committed by Commit Bot
parent b2d4e11579
commit 71a6f0a790
5 changed files with 36 additions and 14 deletions
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2
devices/src/virtio/block.rs
View file

@ -673,7 +673,7 @@ impl Block {
} else {
disk.seek(SeekFrom::Start(offset))
.map_err(|e| ExecuteError::Seek { ioerr: e, sector })?;
disk.write_zeroes(length as usize).map_err(|e| {
disk.write_zeroes_all(length as usize).map_err(|e| {
ExecuteError::DiscardWriteZeroes {
ioerr: Some(e),
sector,

9
qcow/src/qcow.rs
View file

@ -1239,7 +1239,7 @@ impl QcowFile {
if let Some(offset) = self.file_offset_read(curr_addr)? {
// Partial cluster - zero it out.
self.raw_file.file_mut().seek(SeekFrom::Start(offset))?;
self.raw_file.file_mut().write_zeroes(count)?;
self.raw_file.file_mut().write_zeroes_all(count)?;
}
}
@ -1822,8 +1822,7 @@ mod tests {
q.write(&b).expect("Failed to write test string.");
// Overwrite the test data with zeroes.
q.seek(SeekFrom::Start(0xfff2000)).expect("Failed to seek.");
let nwritten = q.write_zeroes(0x200).expect("Failed to write zeroes.");
assert_eq!(nwritten, 0x200);
q.write_zeroes_all(0x200).expect("Failed to write zeroes.");
// Verify that the correct part of the data was zeroed out.
let mut buf = [0u8; 0x1000];
q.seek(SeekFrom::Start(0xfff2000)).expect("Failed to seek.");
@ -1848,8 +1847,8 @@ mod tests {
q.write(&b).expect("Failed to write test string.");
// Overwrite the full cluster with zeroes.
q.seek(SeekFrom::Start(0)).expect("Failed to seek.");
let nwritten = q.write_zeroes(CHUNK_SIZE).expect("Failed to write zeroes.");
assert_eq!(nwritten, CHUNK_SIZE);
q.write_zeroes_all(CHUNK_SIZE)
.expect("Failed to write zeroes.");
// Verify that the data was zeroed out.
let mut buf = [0u8; CHUNK_SIZE];
q.seek(SeekFrom::Start(0)).expect("Failed to seek.");

2
qcow/src/qcow_raw_file.rs
View file

@ -142,7 +142,7 @@ impl QcowRawFile {
pub fn zero_cluster(&mut self, address: u64) -> io::Result<()> {
let cluster_size = self.cluster_size as usize;
self.file.seek(SeekFrom::Start(address))?;
self.file.write_zeroes(cluster_size)?;
self.file.write_zeroes_all(cluster_size)?;
Ok(())
}
}

2
qcow_utils/src/qcow_img.rs
View file

@ -264,7 +264,7 @@ fn dd(file_path: &str, source_path: &str, count: Option<usize>) -> std::result::
let nread = src_file.read(&mut buf[..this_count]).map_err(|_| ())?;
// If this block is all zeros, then use write_zeros so the output file is sparse.
if buf.iter().all(|b| *b == 0) {
qcow_file.write_zeroes(CHUNK_SIZE).map_err(|_| ())?;
qcow_file.write_zeroes_all(CHUNK_SIZE).map_err(|_| ())?;
} else {
qcow_file.write(&buf).map_err(|_| ())?;
}

35
sys_util/src/write_zeroes.rs
View file

@ -4,7 +4,7 @@
use std::cmp::min;
use std::fs::File;
use std::io::{self, Seek, SeekFrom, Write};
use std::io::{self, Error, ErrorKind, Seek, SeekFrom, Write};
use crate::fallocate;
use crate::FallocateMode;
@ -24,8 +24,31 @@ impl PunchHole for File {
/// A trait for writing zeroes to a stream.
pub trait WriteZeroes {
/// Write `length` bytes of zeroes to the stream, returning how many bytes were written.
/// Write up to `length` bytes of zeroes to the stream, returning how many bytes were written.
fn write_zeroes(&mut self, length: usize) -> io::Result<usize>;
/// Write zeroes to the stream until `length` bytes have been written.
///
/// This method will continuously call `write_zeroes` until the requested
/// `length` is satisfied or an error is encountered.
fn write_zeroes_all(&mut self, mut length: usize) -> io::Result<()> {
while length > 0 {
match self.write_zeroes(length) {
Ok(0) => return Err(Error::from(ErrorKind::WriteZero)),
Ok(bytes_written) => {
length = length
.checked_sub(bytes_written)
.ok_or(Error::from(ErrorKind::Other))?
}
Err(e) => {
if e.kind() != ErrorKind::Interrupted {
return Err(e);
}
}
}
}
Ok(())
}
}
impl<T: PunchHole + Seek + Write> WriteZeroes for T {
@ -98,8 +121,8 @@ mod tests {
// Overwrite some of the data with zeroes
f.seek(SeekFrom::Start(2345)).unwrap();
f.write_zeroes(4321).expect("write_zeroes failed");
// Verify seek position after write_zeroes()
f.write_zeroes_all(4321).expect("write_zeroes failed");
// Verify seek position after write_zeroes_all()
assert_eq!(f.seek(SeekFrom::Current(0)).unwrap(), 2345 + 4321);
// Read back the data and verify that it is now zero
@ -147,8 +170,8 @@ mod tests {
// Overwrite some of the data with zeroes
f.seek(SeekFrom::Start(0)).unwrap();
f.write_zeroes(0x10001).expect("write_zeroes failed");
// Verify seek position after write_zeroes()
f.write_zeroes_all(0x10001).expect("write_zeroes failed");
// Verify seek position after write_zeroes_all()
assert_eq!(f.seek(SeekFrom::Current(0)).unwrap(), 0x10001);
// Read back the data and verify that it is now zero