Cancel PutObjectPart on upload abort (#7940)

Calling ListMultipartUploads fails if an upload is aborted while a
part is being uploaded because the directory for the upload exists
(since fsRenameFile ends up calling os.MkdirAll) but the meta JSON file
doesn't. To fix this we make sure an upload hasn't been aborted during
PutObjectPart by checking the existence of the directory for the upload
while moving the temporary part file into it.

cmd/fs-v1-helpers.go

@@ -280,7 +280,7 @@ func fsOpenFile(ctx context.Context, readPath string, offset int64) (io.ReadClos
 	}
 
 	// Stat to get the size of the file at path.
-	st, err := os.Stat(readPath)
+	st, err := fr.Stat()
 	if err != nil {
 		err = osErrToFSFileErr(err)
 		if err != errFileNotFound {
@@ -386,6 +386,26 @@ func fsFAllocate(fd int, offset int64, len int64) (err error) {
 	return nil
 }
 
+// Renames source path to destination path, fails if the destination path
+// parents are not already created.
+func fsSimpleRenameFile(ctx context.Context, sourcePath, destPath string) error {
+	if err := checkPathLength(sourcePath); err != nil {
+		logger.LogIf(ctx, err)
+		return err
+	}
+	if err := checkPathLength(destPath); err != nil {
+		logger.LogIf(ctx, err)
+		return err
+	}
+
+	if err := os.Rename(sourcePath, destPath); err != nil {
+		logger.LogIf(ctx, err)
+		return osErrToFSFileErr(err)
+	}
+
+	return nil
+}
+
 // Renames source path to destination path, creates all the
 // missing parents if they don't exist.
 func fsRenameFile(ctx context.Context, sourcePath, destPath string) error {