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Re: [Qemu-devel] [PATCH 2/2] nbd: fix max_discard
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] nbd: fix max_discard |
Date: |
Mon, 02 Feb 2015 20:55:43 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
Am 02.02.2015 um 19:29 schrieb Denis V. Lunev:
> nbd_co_discard calls nbd_client_session_co_discard which uses uint32_t
> as the length in bytes of the data to discard due to the following
> definition:
>
> struct nbd_request {
> uint32_t magic;
> uint32_t type;
> uint64_t handle;
> uint64_t from;
> uint32_t len; <-- the length of data to be discarded, in bytes
> } QEMU_PACKED;
>
> Thus we should limit bl_max_discard to UINT32_MAX >> BDRV_SECTOR_BITS to
> avoid overflow.
>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Kevin Wolf <address@hidden>
> CC: Peter Lieven <address@hidden>
> ---
> block/nbd.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/block/nbd.c b/block/nbd.c
> index 04cc845..99af713 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -301,6 +301,11 @@ static int nbd_co_flush(BlockDriverState *bs)
> return nbd_client_session_co_flush(&s->client);
> }
>
> +static void nbd_refresh_limits(BlockDriverState *bs, Error **errp)
> +{
> + bs->bl.max_discard = UINT32_MAX >> BDRV_SECTOR_BITS;
> +}
> +
> static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors)
> {
> @@ -396,6 +401,7 @@ static BlockDriver bdrv_nbd = {
> .bdrv_close = nbd_close,
> .bdrv_co_flush_to_os = nbd_co_flush,
> .bdrv_co_discard = nbd_co_discard,
> + .bdrv_refresh_limits = nbd_refresh_limits,
> .bdrv_getlength = nbd_getlength,
> .bdrv_detach_aio_context = nbd_detach_aio_context,
> .bdrv_attach_aio_context = nbd_attach_aio_context,
> @@ -413,6 +419,7 @@ static BlockDriver bdrv_nbd_tcp = {
> .bdrv_close = nbd_close,
> .bdrv_co_flush_to_os = nbd_co_flush,
> .bdrv_co_discard = nbd_co_discard,
> + .bdrv_refresh_limits = nbd_refresh_limits,
> .bdrv_getlength = nbd_getlength,
> .bdrv_detach_aio_context = nbd_detach_aio_context,
> .bdrv_attach_aio_context = nbd_attach_aio_context,
> @@ -430,6 +437,7 @@ static BlockDriver bdrv_nbd_unix = {
> .bdrv_close = nbd_close,
> .bdrv_co_flush_to_os = nbd_co_flush,
> .bdrv_co_discard = nbd_co_discard,
> + .bdrv_refresh_limits = nbd_refresh_limits,
> .bdrv_getlength = nbd_getlength,
> .bdrv_detach_aio_context = nbd_detach_aio_context,
> .bdrv_attach_aio_context = nbd_attach_aio_context,
Reviewed-by: Peter Lieven <address@hidden>