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use BufReader/Writer for Files passed to serde_json::from_reader/writer

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As serde_json will otherwise read files 1 byte at a time.
Writing is a bit better, but syntacitcal elements (quotes, braces,
commas) still often show up as single write syscalls, so use BufWriter
there as well.

Note that while we do store the file in the resulting objects, we do not
need to keep the buffered read/writers as we always `seek` to the
beginning on further file operations.

Reported-by: Mark Schouten <mark@tuxis.nl>
Link: https://lists.proxmox.com/pipermail/pbs-devel/2022-April/004909.html
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
This commit is contained in:
Wolfgang Bumiller
2022-04-06 14:51:12 +02:00
committed by Thomas Lamprecht
parent 085ae87380
commit b300e6fbc2
2 changed files with 7 additions and 7 deletions
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8
proxmox-file-restore/src/block_driver_qemu.rs
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@ -1,7 +1,7 @@
//! Block file access via a small QEMU restore VM using the PBS block driver in QEMU
use std::collections::HashMap;
use std::fs::{File, OpenOptions};
use std::io::{prelude::*, SeekFrom};
use std::io::{prelude::*, BufReader, BufWriter, SeekFrom};
use anyhow::{bail, Error};
use futures::FutureExt;
@ -51,7 +51,7 @@ impl VMStateMap {
fn load() -> Result<Self, Error> {
let mut file = Self::open_file_raw(true)?;
lock_file(&mut file, true, Some(std::time::Duration::from_secs(120)))?;
let map = serde_json::from_reader(&file).unwrap_or_default();
let map = serde_json::from_reader(BufReader::new(&mut file)).unwrap_or_default();
Ok(Self { map, file })
}
@ -59,14 +59,14 @@ impl VMStateMap {
/// shell auto-completion, for anything requiring consistency use load() !
fn load_read_only() -> Result<HashMap<String, VMState>, Error> {
let file = Self::open_file_raw(false)?;
Ok(serde_json::from_reader(&file).unwrap_or_default())
Ok(serde_json::from_reader(BufReader::new(file)).unwrap_or_default())
}
/// Write back a potentially modified state map, consuming the held lock
fn write(mut self) -> Result<(), Error> {
self.file.seek(SeekFrom::Start(0))?;
self.file.set_len(0)?;
serde_json::to_writer(self.file, &self.map)?;
serde_json::to_writer(BufWriter::new(&mut self.file), &self.map)?;
// drop ourselves including file lock
Ok(())