Re: [PATCH 2/2] hw/9pfs: fix alignment issue when host filesystem block size is larger than client msize

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Jevon Qiao <scaleqiao@gmail.com> writes:

> The following patch is to fix alignment issue when host filesystem block 
> size
> is larger than client msize.
>
> Thanks,
> Jevon

That is not the right format to send patch. You can send them as a
series using git-send-email.

>
> From: Jevon Qiao <scaleqiao@gmail.com>
> Date: Sun, 14 Feb 2016 15:11:08 +0800
> Subject: [PATCH] hw/9pfs: fix alignment issue when host filesystem block 
> size
>   is larger than client msize.
>
> Per the previous implementation, iounit will be assigned to be 0 after the
> first if statement as (s->msize - P9_IOHDRSZ)/stbuf.f_bsize will be zero 
> when
> host filesystem block size is larger than msize. Finally, iounit will be 
> equal
> to s->msize - P9_IOHDRSZ, which is usually not aligned.
>
> Signed-off-by: Jevon Qiao <scaleqiao@gmail.com>
> ---
>   hw/9pfs/virtio-9p.c | 19 ++++++++++++++++---
>   1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
> index f972731..005d3a8 100644
> --- a/hw/9pfs/virtio-9p.c
> +++ b/hw/9pfs/virtio-9p.c
> @@ -1326,7 +1326,7 @@ out_nofid:
>   static int32_t get_iounit(V9fsPDU *pdu, V9fsPath *path)
>   {
>       struct statfs stbuf;
> -    int32_t iounit = 0;
> +    int32_t iounit = 0, unit = 0;
>       V9fsState *s = pdu->s;
>
>       /*
> @@ -1334,8 +1334,21 @@ static int32_t get_iounit(V9fsPDU *pdu, V9fsPath 
> *path)
>        * and as well as less than (client msize - P9_IOHDRSZ))
>        */
>       if (!v9fs_co_statfs(pdu, path, &stbuf)) {
> -        iounit = stbuf.f_bsize;
> -        iounit *= (s->msize - P9_IOHDRSZ)/stbuf.f_bsize;
> +    /*
> +     * If host filesystem block size is larger than client msize,
> +     * we will use PAGESIZE as the unit. The reason why we choose
> +     * PAGESIZE is because the data will be splitted in terms of
> +     * PAGESIZE in the virtio layer. In this case, the final
> +     * iounit is equal to the value of ((msize/unit) - 1) * unit.
> +     */
> +    if (stbuf.f_bsize > s->msize) {
> +        iounit = 4096;
> +        unit = 4096;

What page size it should be guest or host ?. Also why 4096 ?. ppc64 use
64K page size.


> +    } else {
> +            iounit = stbuf.f_bsize;
> +        unit = stbuf.f_bsize;
> +    }
> +        iounit *= (s->msize - P9_IOHDRSZ)/unit;
>       }
>       if (!iounit) {
>           iounit = s->msize - P9_IOHDRSZ;
> -- 

-aneesh