From ba1d1afdfeeb5ec6cbfd0052ab298d9b7cb7e5ba Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Mon, 25 Jul 2011 19:42:37 +0200 Subject: [PATCH] posix-aio-compat: Allow read after EOF In order to be able to transparently replace bdrv_read calls by bdrv_co_read, reading beyond EOF must produce zeros instead of short reads for AIO, too. Signed-off-by: Kevin Wolf --- posix-aio-compat.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/posix-aio-compat.c b/posix-aio-compat.c index 788d113860..8dc00cbb0f 100644 --- a/posix-aio-compat.c +++ b/posix-aio-compat.c @@ -198,6 +198,12 @@ static ssize_t handle_aiocb_rw_vector(struct qemu_paiocb *aiocb) return len; } +/* + * Read/writes the data to/from a given linear buffer. + * + * Returns the number of bytes handles or -errno in case of an error. Short + * reads are only returned if the end of the file is reached. + */ static ssize_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf) { ssize_t offset = 0; @@ -334,6 +340,19 @@ static void *aio_thread(void *unused) switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) { case QEMU_AIO_READ: + ret = handle_aiocb_rw(aiocb); + if (ret >= 0 && ret < aiocb->aio_nbytes && aiocb->common.bs->growable) { + /* A short read means that we have reached EOF. Pad the buffer + * with zeros for bytes after EOF. */ + QEMUIOVector qiov; + + qemu_iovec_init_external(&qiov, aiocb->aio_iov, + aiocb->aio_niov); + qemu_iovec_memset_skip(&qiov, 0, aiocb->aio_nbytes - ret, ret); + + ret = aiocb->aio_nbytes; + } + break; case QEMU_AIO_WRITE: ret = handle_aiocb_rw(aiocb); break;