client: pxar: add method for metadata comparison

Add method to compare metadata of current file entry against metadata
of the entry looked up in the previous backup snapshot. If the
metadata matched, the start offset pointing to the files payload
header in the payload steam is returned.

This is in preparation for reusing payload chunks for unchanged files.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>

diff --git a/pbs-client/src/pxar/create.rs b/pbs-client/src/pxar/create.rs
index d183d3f6bc27b4b28f97f28c60718ae9a7a3e673..1cf11fc0846527c8a072a7e52cf0a715f98d2d00 100644 (file)
--- a/pbs-client/src/pxar/create.rs
+++ b/pbs-client/src/pxar/create.rs
@@ -2,6 +2,7 @@ use std::collections::{HashMap, HashSet};
 use std::ffi::{CStr, CString, OsStr};
 use std::fmt;
 use std::io::{self, Read};
+use std::mem::size_of;
 use std::ops::Range;
 use std::os::unix::ffi::OsStrExt;
 use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
@@ -21,7 +22,7 @@ use proxmox_sys::error::SysError;
 use pxar::accessor::aio::{Accessor, Directory};
 use pxar::accessor::ReadAt;
 use pxar::encoder::{LinkOffset, SeqWrite};
-use pxar::{Metadata, PxarVariant};
+use pxar::{EntryKind, Metadata, PxarVariant};
 
 use proxmox_io::vec;
 use proxmox_lang::c_str;
@@ -333,6 +334,40 @@ impl Archiver {
         .boxed()
     }
 
+    async fn is_reusable_entry(
+        &mut self,
+        previous_metadata_accessor: &Option<Directory<MetadataArchiveReader>>,
+        file_name: &Path,
+        metadata: &Metadata,
+    ) -> Result<Option<Range<u64>>, Error> {
+        if let Some(previous_metadata_accessor) = previous_metadata_accessor {
+            if let Some(file_entry) = previous_metadata_accessor.lookup(file_name).await? {
+                if metadata == file_entry.metadata() {
+                    if let EntryKind::File {
+                        payload_offset: Some(offset),
+                        size,
+                        ..
+                    } = file_entry.entry().kind()
+                    {
+                        let range =
+                            *offset..*offset + size + size_of::<pxar::format::Header>() as u64;
+                        log::debug!(
+                            "reusable: {file_name:?} at range {range:?} has unchanged metadata."
+                        );
+                        return Ok(Some(range));
+                    }
+                    log::debug!("reencode: {file_name:?} not a regular file.");
+                    return Ok(None);
+                }
+                log::debug!("reencode: {file_name:?} metadata did not match.");
+                return Ok(None);
+            }
+            log::debug!("reencode: {file_name:?} not found in previous archive.");
+        }
+
+        Ok(None)
+    }
+
     /// openat() wrapper which allows but logs `EACCES` and turns `ENOENT` into `None`.
     ///
     /// The `existed` flag is set when iterating through a directory to note that we know the file