[pbs-devel] [PATCH proxmox-backup v4 1/1] pxar/extract: if possible create files sparesly

[Dominik Csapak <d.csapak@proxmox.com>]

instead of filling them with zeroes

this fixes an issue where we could not restore a container with large
sparse files in the backup (e.g. a 10GiB sparse file in a container
with a 8GiB disk)

if the last operation of the copy was a seek, we need to truncate
the file to the correct size (seek beyond filesize does not change it)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/pxar/extract.rs | 43 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/src/pxar/extract.rs b/src/pxar/extract.rs
index 0a61c885..80095e3f 100644
--- a/src/pxar/extract.rs
+++ b/src/pxar/extract.rs
@@ -18,7 +18,10 @@ use pxar::format::Device;
 use pxar::Metadata;
 
 use proxmox::c_result;
-use proxmox::tools::fs::{create_path, CreateOptions};
+use proxmox::tools::{
+    fs::{create_path, CreateOptions},
+    io::{sparse_copy, sparse_copy_async},
+};
 
 use crate::pxar::dir_stack::PxarDirStack;
 use crate::pxar::metadata;
@@ -406,10 +409,23 @@ impl Extractor {
         )
         .map_err(|err| format_err!("failed to apply initial flags: {}", err))?;
 
-        let extracted = io::copy(&mut *contents, &mut file)
+        let result = sparse_copy(&mut *contents, &mut file)
             .map_err(|err| format_err!("failed to copy file contents: {}", err))?;
-        if size != extracted {
-            bail!("extracted {} bytes of a file of {} bytes", extracted, size);
+
+        if size != result.written {
+            bail!(
+                "extracted {} bytes of a file of {} bytes",
+                result.written,
+                size
+            );
+        }
+
+        if result.seeked_last {
+            while match nix::unistd::ftruncate(file.as_raw_fd(), size as i64) {
+                Ok(_) => false,
+                Err(nix::Error::Sys(errno)) if errno == nix::errno::Errno::EINTR => true,
+                Err(err) => bail!("error setting file size: {}", err),
+            } {}
         }
 
         metadata::apply(
@@ -449,11 +465,24 @@ impl Extractor {
         )
         .map_err(|err| format_err!("failed to apply initial flags: {}", err))?;
 
-        let extracted = tokio::io::copy(&mut *contents, &mut file)
+        let result = sparse_copy_async(&mut *contents, &mut file)
             .await
             .map_err(|err| format_err!("failed to copy file contents: {}", err))?;
-        if size != extracted {
-            bail!("extracted {} bytes of a file of {} bytes", extracted, size);
+
+        if size != result.written {
+            bail!(
+                "extracted {} bytes of a file of {} bytes",
+                result.written,
+                size
+            );
+        }
+
+        if result.seeked_last {
+            while match nix::unistd::ftruncate(file.as_raw_fd(), size as i64) {
+                Ok(_) => false,
+                Err(nix::Error::Sys(errno)) if errno == nix::errno::Errno::EINTR => true,
+                Err(err) => bail!("error setting file size: {}", err),
+            } {}
         }
 
         metadata::apply(
-- 
2.20.1