A method for data transfer includes receiving in an input/output (I/O) operation data to be written to a specified virtual address in a host memory. Upon receiving the data, it is detected that a first page that contains the specified virtual address is swapped out of the host memory. Responsively to detecting that the first page is swapped out, the received data are written to a second, free page in the host memory, and the specified virtual address is remapped to the free page.