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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 <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2011-07-25 19:42:37 +02:00
parent e680cfa7e2
commit ba1d1afdfe
1 changed files with 19 additions and 0 deletions
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19
posix-aio-compat.c
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@ -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;