storage rework

pkg/cowutils/dedupe.go

@@ -0,0 +1,88 @@
+package cowutils
+
+import (
+	"context"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func DedupeFiles(ctx context.Context, paths []string) (deduped uint64, err error) {
+	srcF, err := os.Open(paths[0])
+	if err != nil {
+		return deduped, err
+	}
+	defer srcF.Close()
+	srcStat, err := srcF.Stat()
+	if err != nil {
+		return deduped, err
+	}
+
+	srcFd := int(srcF.Fd())
+	srcSize := srcStat.Size()
+
+	fsStat := unix.Statfs_t{}
+	err = unix.Fstatfs(srcFd, &fsStat)
+	if err != nil {
+		return deduped, err
+	}
+
+	if int64(fsStat.Bsize) > srcSize { // for btrfs it means file residing in metadata and can't be deduplicated
+		return deduped, nil
+	}
+
+	blockSize := uint64((srcSize % int64(fsStat.Bsize)) * int64(fsStat.Bsize))
+
+	fdr := unix.FileDedupeRange{
+		Src_offset: 0,
+		Src_length: blockSize,
+		Info:       []unix.FileDedupeRangeInfo{},
+	}
+
+	for _, dst := range paths[1:] {
+		if ctx.Err() != nil {
+			return deduped, ctx.Err()
+		}
+
+		destF, err := os.OpenFile(dst, os.O_RDWR, os.ModePerm)
+		if err != nil {
+			return deduped, err
+		}
+
+		// defer in cycle is intended, file must be closed only at the end of the function,
+		// and, most importantly, this keeps GC from closing descriptor while dudupe in progress
+		defer destF.Close()
+
+		fdr.Info = append(fdr.Info, unix.FileDedupeRangeInfo{
+			Dest_fd:     int64(destF.Fd()),
+			Dest_offset: 0,
+		})
+	}
+
+	if len(fdr.Info) == 0 {
+		return deduped, nil
+	}
+
+	if ctx.Err() != nil {
+		return deduped, ctx.Err()
+	}
+
+	fdr.Src_offset = 0
+	for i := range fdr.Info {
+		fdr.Info[i].Dest_offset = 0
+	}
+
+	err = unix.IoctlFileDedupeRange(srcFd, &fdr)
+	if err != nil {
+		return deduped, err
+	}
+
+	for i := range fdr.Info {
+		deduped += fdr.Info[i].Bytes_deduped
+
+		fdr.Info[i].Status = 0
+		fdr.Info[i].Bytes_deduped = 0
+	}
+
+	return deduped, nil
+}