static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb) { ssize_t nbytes; char *buf; if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) { /* * If there is just a single buffer, and it is properly aligned * we can just use plain pread/pwrite without any problems. */ if (aiocb->aio_niov == 1) { return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base); } /* * We have more than one iovec, and all are properly aligned. * * Try preadv/pwritev first and fall back to linearizing the * buffer if it's not supported. */ if (preadv_present) { nbytes = handle_aiocb_rw_vector(aiocb); if (nbytes == aiocb->aio_nbytes || (nbytes < 0 && nbytes != -ENOSYS)) { return nbytes; } preadv_present = false; } /* * XXX(hch): short read/write. no easy way to handle the reminder * using these interfaces. For now retry using plain * pread/pwrite? */ } /* * Ok, we have to do it the hard way, copy all segments into * a single aligned buffer. */ buf = qemu_blockalign(aiocb->bs, aiocb->aio_nbytes); if (aiocb->aio_type & QEMU_AIO_WRITE) { char *p = buf; int i; for (i = 0; i < aiocb->aio_niov; ++i) { memcpy(p, aiocb->aio_iov[i].iov_base, aiocb->aio_iov[i].iov_len); p += aiocb->aio_iov[i].iov_len; } assert(p - buf == aiocb->aio_nbytes); } nbytes = handle_aiocb_rw_linear(aiocb, buf); if (!(aiocb->aio_type & QEMU_AIO_WRITE)) { char *p = buf; size_t count = aiocb->aio_nbytes, copy; int i; for (i = 0; i < aiocb->aio_niov && count; ++i) { copy = count; if (copy > aiocb->aio_iov[i].iov_len) { copy = aiocb->aio_iov[i].iov_len; } memcpy(aiocb->aio_iov[i].iov_base, p, copy); assert(count >= copy); p += copy; count -= copy; } assert(count == 0); } qemu_vfree(buf); return nbytes; }