ksud: reclaim sparse space when install/uninstall modules. close #1367

userspace/ksud/src/utils.rs

@@ -231,3 +231,88 @@ pub fn copy_sparse_file<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> Resul
 
     Ok(())
 }
+
+pub fn punch_hole(src: impl AsRef<Path>) -> Result<()> {
+    let mut src_file = OpenOptions::new().write(true).read(true).open(src)?;
+
+    let st = rustix::fs::fstat(&src_file)?;
+
+    let bufsz = st.st_blksize;
+    let mut buf = vec![0u8; bufsz as usize];
+
+    let mut ct = 0;
+    let mut hole_sz = 0;
+    let mut hole_start = 0;
+
+    let segments = src_file.scan_chunks()?;
+    for segment in segments {
+        if segment.segment_type != SegmentType::Data {
+            continue;
+        }
+
+        let mut off = segment.start;
+        let end = segment.end + 1;
+
+        while off < end {
+            let mut rsz = rustix::io::pread(&src_file, &mut buf, off)? as u64;
+            if rsz > 0 && rsz > end - off {
+                // exceed the end of the boundary
+                rsz = end - off;
+            }
+
+            if rsz == 0 {
+                break;
+            }
+
+            if buf.iter().all(|&x| x == 0) {
+                // the whole buf is zero, mark it as a hole
+                if hole_sz == 0 {
+                    hole_start = off;
+                }
+                // for continuous zero, we can merge them into a bigger hole
+                hole_sz += rsz;
+            } else if hole_sz > 0 {
+                if let Err(e) = rustix::fs::fallocate(
+                    &src_file,
+                    rustix::fs::FallocateFlags::PUNCH_HOLE | rustix::fs::FallocateFlags::KEEP_SIZE,
+                    hole_start,
+                    hole_sz,
+                ) {
+                    log::warn!("Failed to punch hole: {:?}", e);
+                }
+
+                ct += hole_sz;
+
+                hole_sz = 0;
+                hole_start = 0;
+            }
+
+            off += rsz;
+        }
+
+        // if the last segment is a hole, we need to punch it
+        if hole_sz > 0 {
+            let mut alloc_sz = hole_sz;
+            if off >= end {
+                alloc_sz += st.st_blksize as u64;
+            }
+            if let Err(e) = rustix::fs::fallocate(
+                &src_file,
+                rustix::fs::FallocateFlags::PUNCH_HOLE | rustix::fs::FallocateFlags::KEEP_SIZE,
+                hole_start,
+                alloc_sz,
+            ) {
+                log::warn!("Failed to punch hole: {:?}", e);
+            }
+
+            ct += hole_sz;
+        }
+    }
+
+    log::info!(
+        "Punched {} of hole",
+        humansize::format_size(ct, humansize::DECIMAL)
+    );
+
+    Ok(())
+}