From: Dietmar Maurer <dietmar@proxmox.com>
To: pbs-devel@lists.proxmox.com
Subject: [pbs-devel] [PATCH proxmox] add fsync parameter to replace_file and atomic_open_or_create
Date: Wed, 20 Oct 2021 15:00:43 +0200 [thread overview]
Message-ID: <20211020130045.2020043-1-dietmar@proxmox.com> (raw)
The fsync is required for consistency after power failure, so it should
be set when writing config files or otherwise important data.
---
proxmox/src/tools/fs.rs | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/proxmox/src/tools/fs.rs b/proxmox/src/tools/fs.rs
index 19e549d..29233dd 100644
--- a/proxmox/src/tools/fs.rs
+++ b/proxmox/src/tools/fs.rs
@@ -163,10 +163,15 @@ pub fn make_tmp_file<P: AsRef<Path>>(
/// Atomically replace a file.
///
/// This first creates a temporary file and then rotates it in place.
+///
+/// `fsync`: use `fsync(2)` sycall to synchronize a file's in-core
+/// state with storage device. This makes sure the is consistent even
+/// aftert a power loss.
pub fn replace_file<P: AsRef<Path>>(
path: P,
data: &[u8],
options: CreateOptions,
+ fsync: bool,
) -> Result<(), Error> {
let (fd, tmp_path) = make_tmp_file(&path, options)?;
@@ -177,6 +182,11 @@ pub fn replace_file<P: AsRef<Path>>(
bail!("write failed: {}", err);
}
+ if fsync {
+ // make sure data is on disk
+ nix::unistd::fsync(file.as_raw_fd())?;
+ }
+
if let Err(err) = std::fs::rename(&tmp_path, &path) {
let _ = unistd::unlink(&tmp_path);
bail!(
@@ -194,11 +204,16 @@ pub fn replace_file<P: AsRef<Path>>(
/// Since we need to initialize the file, we also need a solid slow
/// path where we create the file. In order to avoid races, we create
/// it in a temporary location and rotate it in place.
+///
+/// `fsync`: use `fsync(2)` sycall to synchronize the `initial_data`
+/// to the storage device. This options has no effect it the `initial_data`
+/// is empty or the file already exists.
pub fn atomic_open_or_create_file<P: AsRef<Path>>(
path: P,
mut oflag: OFlag,
initial_data: &[u8],
options: CreateOptions,
+ fsync: bool,
) -> Result<File, Error> {
let path = path.as_ref();
@@ -244,6 +259,10 @@ pub fn atomic_open_or_create_file<P: AsRef<Path>>(
err,
)
})?;
+ if fsync {
+ // make sure the initial_data is on disk
+ nix::unistd::fsync(file.as_raw_fd())?;
+ }
}
// rotate the file into place, but use `RENAME_NOREPLACE`, so in case 2 processes race against
@@ -623,6 +642,7 @@ pub fn open_file_locked<P: AsRef<Path>>(
OFlag::O_RDWR | OFlag::O_CLOEXEC | OFlag::O_APPEND,
&[],
options,
+ false,
)?;
match lock_file(&mut file, exclusive, Some(timeout)) {
--
2.30.2
next reply other threads:[~2021-10-20 13:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-20 13:00 Dietmar Maurer [this message]
2021-10-20 13:00 ` [pbs-devel] [PATCH proxmox-opendid] add fsync parameter to replace_file Dietmar Maurer
2021-10-20 13:00 ` [pbs-devel] [PATCH proxmox-backup] use new fsync parameter to replace_file and atomic_open_or_create Dietmar Maurer
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