Re: [Qemu-devel] [PATCH 1/2] raw-posix: fix O_DIRECT short reads

[Benoît Canet]

The Thursday 21 Aug 2014 à 13:44:07 (+0100), Stefan Hajnoczi wrote :
> The following O_DIRECT read from a <512 byte file fails:
> 
>   $ truncate -s 320 test.img
>   $ qemu-io -n -c 'read -P 0 0 512' test.img
>   qemu-io: can't open device test.img: Could not read image for determining 
> its format: Invalid argument
> 
> Note that qemu-io completes successfully without the -n (O_DIRECT)
> option.
> 
> This patch fixes qemu-iotests ./check -nocache -vmdk 059.
> 
> Suggested-by: Kevin Wolf <address@hidden>
> Reported-by: Markus Armbruster <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>  block/raw-posix.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 1194eb0..a48ce91 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -747,6 +747,15 @@ static ssize_t handle_aiocb_rw_linear(RawPosixAIOData 
> *aiocb, char *buf)
>          }
>          if (len == -1 && errno == EINTR) {
>              continue;
> +        } else if (len == -1 && errno == EINVAL &&
> +                   (aiocb->bs->open_flags & BDRV_O_NOCACHE) &&
> +                   !(aiocb->aio_type & QEMU_AIO_WRITE) &&
> +                   offset > 0) {
> +            /* O_DIRECT pread() may fail with EINVAL when offset is unaligned
> +             * after a short read.  Assume that O_DIRECT short reads only 
> occur
> +             * at EOF.  Therefore this is a short read, not an I/O error.
> +             */
> +            break;
>          } else if (len == -1) {
>              offset = -errno;
>              break;
> -- 
> 1.9.3
> 
> 
Reviewed-by: Benoît Canet <address@hidden>