diff --git a/backend/posix/posix.go b/backend/posix/posix.go
index 6fd3caf..50f4456 100644
--- a/backend/posix/posix.go
+++ b/backend/posix/posix.go
@@ -234,7 +234,7 @@ func (p *Posix) CompleteMultipartUpload(bucket, object, uploadID string, parts [
 		}
 	}
 
-	f, err := openTmpFile(metaTmpDir, object)
+	f, err := openTmpFile(metaTmpDir, object, 0)
 	if err != nil {
 		return nil, fmt.Errorf("open temp file: %w", err)
 	}
@@ -681,7 +681,7 @@ func (p *Posix) PutObjectPart(bucket, object, uploadID string, part int, length
 	objdir := filepath.Join(bucket, metaTmpMultipartDir, fmt.Sprintf("%x", sum))
 	partPath := filepath.Join(objdir, uploadID, fmt.Sprintf("%v", part))
 
-	f, err := openTmpFile(objdir, partPath)
+	f, err := openTmpFile(objdir, partPath, length)
 	if err != nil {
 		return "", fmt.Errorf("open temp file: %w", err)
 	}
@@ -734,7 +734,7 @@ func (p *Posix) PutObject(po *s3.PutObjectInput) (string, error) {
 		xattr.Set(name, dirObjKey, nil)
 	} else {
 		// object is file
-		f, err := openTmpFile(metaTmpDir, *po.Key)
+		f, err := openTmpFile(metaTmpDir, *po.Key, po.ContentLength)
 		if err != nil {
 			return "", fmt.Errorf("open temp file: %w", err)
 		}
diff --git a/backend/posix/posix_darwin.go b/backend/posix/posix_darwin.go
index 6a4739e..ee7103a 100644
--- a/backend/posix/posix_darwin.go
+++ b/backend/posix/posix_darwin.go
@@ -13,7 +13,7 @@ type tmpfile struct {
 	objname string
 }
 
-func openTmpFile(dir, obj string) (*tmpfile, error) {
+func openTmpFile(dir, obj string, size int64) (*tmpfile, error) {
 	// Create a temp file for upload while in progress (see link comments below).
 	f, err := os.CreateTemp(dir,
 		fmt.Sprintf("%x\n", sha256.Sum256([]byte(obj))))
diff --git a/backend/posix/posix_linux.go b/backend/posix/posix_linux.go
index 123533c..6135372 100644
--- a/backend/posix/posix_linux.go
+++ b/backend/posix/posix_linux.go
@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 	"strconv"
+	"syscall"
 
 	"golang.org/x/sys/unix"
 )
@@ -20,7 +21,7 @@ type tmpfile struct {
 	isOTmp  bool
 }
 
-func openTmpFile(dir, obj string) (*tmpfile, error) {
+func openTmpFile(dir, obj string, size int64) (*tmpfile, error) {
 	// O_TMPFILE allows for a file handle to an unnamed file in the filesystem.
 	// This can help reduce contention within the namespace (parent directories),
 	// etc. And will auto cleanup the inode on close if we never link this
@@ -35,11 +36,29 @@ func openTmpFile(dir, obj string) (*tmpfile, error) {
 		if err != nil {
 			return nil, err
 		}
-		return &tmpfile{f: f}, nil
+		tmp := &tmpfile{f: f}
+		// falloc is best effort, its fine if this fails
+		if size > 0 {
+			tmp.falloc(size)
+		}
+		return tmp, nil
 	}
 
 	f := os.NewFile(uintptr(fd), filepath.Join(procfddir, strconv.Itoa(fd)))
-	return &tmpfile{f: f, isOTmp: true}, nil
+	tmp := &tmpfile{f: f, isOTmp: true}
+	// falloc is best effort, its fine if this fails
+	if size > 0 {
+		tmp.falloc(size)
+	}
+	return tmp, nil
+}
+
+func (tmp *tmpfile) falloc(size int64) error {
+	err := syscall.Fallocate(int(tmp.f.Fd()), 0, 0, size)
+	if err != nil {
+		return fmt.Errorf("fallocate: %v", err)
+	}
+	return nil
 }
 
 func (tmp *tmpfile) link() error {