Re: [Qemu-devel] [PATCH 5/8] block: Evaluate @exact in protocol drivers

[Maxim Levitsky <mlevitsk@redhat.com>]

On Wed, 2019-09-18 at 11:51 +0200, Max Reitz wrote:
> We have two protocol drivers that return success when trying to shrink a
> block device even though they cannot shrink it.  This behavior is now
> only allowed with exact=false, so they should return an error with
> exact=true.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/file-posix.c | 8 +++++++-
>  block/iscsi.c      | 7 ++++++-
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/block/file-posix.c b/block/file-posix.c
> index d8755c5fac..a85f3486d1 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -2028,6 +2028,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>      }
>  
>      if (S_ISREG(st.st_mode)) {
> +        /* Always resizes to the exact @offset */
>          return raw_regular_truncate(bs, s->fd, offset, prealloc, errp);
>      }
>  
> @@ -2038,7 +2039,12 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>      }
>  
>      if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode)) {
> -        if (offset > raw_getlength(bs)) {
> +        int64_t cur_length = raw_getlength(bs);
> +
> +        if (offset != cur_length && exact) {
> +            error_setg(errp, "Cannot resize device files");
> +            return -ENOTSUP;
> +        } else if (offset > cur_length) {
>              error_setg(errp, "Cannot grow device files");
>              return -EINVAL;
>          }
> diff --git a/block/iscsi.c b/block/iscsi.c
> index a90426270a..cc2072ff6c 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -2126,6 +2126,7 @@ static int coroutine_fn iscsi_co_truncate(BlockDriverState *bs, int64_t offset,
>                                            Error **errp)
>  {
>      IscsiLun *iscsilun = bs->opaque;
> +    int64_t cur_length;
>      Error *local_err = NULL;
>  
>      if (prealloc != PREALLOC_MODE_OFF) {
> @@ -2145,7 +2146,11 @@ static int coroutine_fn iscsi_co_truncate(BlockDriverState *bs, int64_t offset,
>          return -EIO;
>      }
>  
> -    if (offset > iscsi_getlength(bs)) {
> +    cur_length = iscsi_getlength(bs);
> +    if (offset != cur_length && exact) {
> +        error_setg(errp, "Cannot resize iSCSI devices");
> +        return -ENOTSUP;
> +    } else if (offset > cur_length) {
>          error_setg(errp, "Cannot grow iSCSI devices");
>          return -EINVAL;
>      }

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Best regards,
	Maxim Levitsky