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From: Stefan Reiter <s.reiter@proxmox.com>
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Date: Thu, 22 Oct 2020 17:34:19 +0200
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Subject: [pve-devel] [PATCH proxmox-backup-qemu 3/4] add state serializing
and loading functions
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For dirty-bitmap migration, QEMU also needs to move the static state of
the library to the target. proxmox_{import,export}_state provide a means
of accessing said data in a serialized fashion.
QEMU treats the state as some unknown quantity of bytes and the result
does not need to be human-readable, so we encode it with 'bincode',
which is based on serde.
Since the quantity is only known *after* serialization, we have to
allocate the buffer ourselves. This is handled by Box::leak-ing a Rust
allocated buffer and cleaning up via the explicit
proxmox_free_state_buf function.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
---
I'm not sure we use 'bincode' anywhere else, but it is packaged for debian
already and seemed like a good fit. Alternatively, we could of course use our
already existing dependency on serde_json and just serialize to a JSON string.
Cargo.toml | 1 +
current-api.h | 20 ++++++++++++++++++++
src/commands.rs | 19 +++++++++++++++++++
src/lib.rs | 34 ++++++++++++++++++++++++++++++++++
4 files changed, 74 insertions(+)
diff --git a/Cargo.toml b/Cargo.toml
index d51ba93..ca93b36 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -28,3 +28,4 @@ proxmox-backup = { git = "git://git.proxmox.com/git/proxmox-backup.git", tag = "
#proxmox-backup = { path = "../proxmox-backup" }
serde_json = "1.0"
tokio = { version = "0.2.9", features = [ "blocking", "fs", "io-util", "macros", "rt-threaded", "signal", "stream", "tcp", "time", "uds" ] }
+bincode = "1.0"
diff --git a/current-api.h b/current-api.h
index d77eff6..77e8c4b 100644
--- a/current-api.h
+++ b/current-api.h
@@ -263,6 +263,26 @@ void proxmox_backup_write_data_async(ProxmoxBackupHandle *handle,
int *result,
char **error);
+/**
+ * Serialize all state data into a byte buffer. Can be loaded again with
+ * proxmox_import_state. Use for migration for example.
+ *
+ * Length of the returned buffer is written to buf_size. Returned buffer must
+ * be freed with proxmox_free_state_buf.
+ */
+uint8_t *proxmox_export_state(uintptr_t *buf_size);
+
+/**
+ * Free a buffer acquired from proxmox_export_state.
+ */
+void proxmox_free_state_buf(uint8_t *buf);
+
+/**
+ * Load state serialized by proxmox_export_state. If loading fails, a message
+ * will be logged to stderr, but the function will not fail.
+ */
+void proxmox_import_state(const uint8_t *buf, uintptr_t buf_size);
+
/**
* Open connection to the backup server (sync)
*
diff --git a/src/commands.rs b/src/commands.rs
index f7e0f62..7a24b7c 100644
--- a/src/commands.rs
+++ b/src/commands.rs
@@ -16,6 +16,9 @@ use crate::upload_queue::*;
use lazy_static::lazy_static;
lazy_static!{
+ // Note: Any state stored here that needs to be sent along with migration
+ // needs to be specified in (de)serialize_state as well!
+
static ref PREVIOUS_CSUMS: Mutex<HashMap<String, [u8;32]>> = {
Mutex::new(HashMap::new())
};
@@ -35,6 +38,22 @@ pub struct ImageUploadInfo {
}
+pub(crate) fn serialize_state() -> Vec<u8> {
+ let prev_csums = &*PREVIOUS_CSUMS.lock().unwrap();
+ let prev_crypt_digest = &*PREVIOUS_CRYPT_CONFIG_DIGEST.lock().unwrap();
+ bincode::serialize(&(prev_csums, prev_crypt_digest)).unwrap()
+}
+
+pub(crate) fn deserialize_state(data: &[u8]) -> Result<(), Error> {
+ let (prev_csums, prev_crypt_digest) = bincode::deserialize(data)?;
+ let mut prev_csums_guard = PREVIOUS_CSUMS.lock().unwrap();
+ let mut prev_crypt_digest_guard = PREVIOUS_CRYPT_CONFIG_DIGEST.lock().unwrap();
+ *prev_csums_guard = prev_csums;
+ *prev_crypt_digest_guard = prev_crypt_digest;
+ Ok(())
+}
+
+
// Note: We alway register/upload a chunk containing zeros
async fn register_zero_chunk(
client: Arc<BackupWriter>,
diff --git a/src/lib.rs b/src/lib.rs
index b9ca905..8511cbf 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -967,3 +967,37 @@ pub extern "C" fn proxmox_restore_read_image_at_async(
callback_info.send_result(result);
});
}
+
+/// Serialize all state data into a byte buffer. Can be loaded again with
+/// proxmox_import_state. Use for migration for example.
+///
+/// Length of the returned buffer is written to buf_size. Returned buffer must
+/// be freed with proxmox_free_state_buf.
+#[no_mangle]
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub extern "C" fn proxmox_export_state(buf_size: *mut usize) -> *mut u8 {
+ let data = commands::serialize_state().into_boxed_slice();
+ unsafe { *buf_size = data.len(); }
+ Box::leak(data).as_mut_ptr()
+}
+
+/// Load state serialized by proxmox_export_state. If loading fails, a message
+/// will be logged to stderr, but the function will not fail.
+#[no_mangle]
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub extern "C" fn proxmox_import_state(buf: *const u8, buf_size: usize) {
+ let data = unsafe { std::slice::from_raw_parts(buf, buf_size) };
+ // ignore errors, just log what happened
+ if let Err(err) = commands::deserialize_state(data) {
+ eprintln!("error deserializing PBS state - {}", err);
+ }
+}
+
+/// Free a buffer acquired from proxmox_export_state.
+#[no_mangle]
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub extern "C" fn proxmox_free_state_buf(buf: *mut u8) {
+ if !buf.is_null() {
+ unsafe { Box::from_raw(buf); }
+ }
+}
--
2.20.1