Re: [PATCH] block: Return the real error code in bdrv_getlength
On 11/4/20 9:10 PM, Tuguoyi wrote: > The return code from bdrv_nb_sectors() should be checked before doing > the following sanity check. > > Signed-off-by: Guoyi Tu It looks like you sent several variations on this patch. A meta-observation: your mailer is attributing the patch to the spelling "Tuguoyi", while your S-o-b line is spelling "Guoyi Tu". It's worth being consistent between the two. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
Re: [PATCH] block: Return the real error code in bdrv_getlength
On 11/4/20 11:41 PM, Tuguoyi wrote:
> Sorry, please ignore this patch, it's not a right fix
What's not right about it?
>> +++ b/block.c
>> @@ -5082,6 +5082,10 @@ int64_t bdrv_getlength(BlockDriverState *bs)
>> {
>> int64_t ret = bdrv_nb_sectors(bs);
>>
>> +if (ret < 0) {
>> +return ret;
>> +}
>> +
>> ret = ret > INT64_MAX / BDRV_SECTOR_SIZE ? -EFBIG : ret;
You are correct that the old code was broken (since
INT64_MAX/BDRV_SECTOR_SIZE is unsigned, any negative ret is likewise
promoted to unsigned and we mistakenly return -EFBIG instead of the
original error). But your new code works just fine: because we
guarantee with the early return above that ret is a positive value, it
doesn't matter that the rest of this ?: is performed in unsigned math.
>> return ret < 0 ? ret : ret * BDRV_SECTOR_SIZE;
Of course, having two ?: in a row is odd; we could instead write:
if (ret < 0){
return ret;
}
if (ret > INT64_MAX / BDRV_SECTOR_SIZE) {
return -EFBIG;
}
return ret * BDRV_SECTOR_SIZE;
for the same result.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
RE: [PATCH] block: Return the real error code in bdrv_getlength
Sorry, please ignore this patch, it's not a right fix
--
Best regards,
Guoyi
> -Original Message-
> From: tuguoyi (Cloud)
> Sent: Thursday, November 05, 2020 11:11 AM
> To: 'Kevin Wolf' ; 'Max Reitz' ;
> 'qemu-block@nongnu.org'
> Cc: 'qemu-de...@nongnu.org'
> Subject: [PATCH] block: Return the real error code in bdrv_getlength
>
> The return code from bdrv_nb_sectors() should be checked before doing
> the following sanity check.
>
> Signed-off-by: Guoyi Tu
> ---
> block.c | 4
> 1 file changed, 4 insertions(+)
>
> diff --git a/block.c b/block.c
> index 430edf7..19ebbc0 100644
> --- a/block.c
> +++ b/block.c
> @@ -5082,6 +5082,10 @@ int64_t bdrv_getlength(BlockDriverState *bs)
> {
> int64_t ret = bdrv_nb_sectors(bs);
>
> +if (ret < 0) {
> +return ret;
> +}
> +
> ret = ret > INT64_MAX / BDRV_SECTOR_SIZE ? -EFBIG : ret;
> return ret < 0 ? ret : ret * BDRV_SECTOR_SIZE;
> }
> --
> 2.7.4
>
>
> --
> Best regards,
> Guoyi
>
