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Date: Fri, 03 Apr 2015 17:44:31 +0300
From: Michael Tokarev <mjt@tls.msk.ru>
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Subject: Re: [Qemu-devel] [PATCH] nbd/trivial: fix type cast for ioctl
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To: Paolo Bonzini <pbonzini@redhat.com>, Bogdan Purcareata <bogdan.purcareata@freescale.com>, qemu-devel@nongnu.org, qemu-stable <qemu-stable@nongnu.org>

03.04.2015 17:15, Paolo Bonzini wrote:
> On 03/04/2015 13:01, Bogdan Purcareata wrote:
...
>> -    if (ioctl(fd, NBD_SET_SIZE_BLOCKS, size / (size_t)BDRV_SECTOR_SIZE) < 0) {
>> +    if (ioctl(fd, NBD_SET_SIZE_BLOCKS, (size_t)(size / BDRV_SECTOR_SIZE) < 0)) {
>>          int serrno = errno;

Hmm..  I don't think this is right at all.  Now we compare size_t with zero,
the result is always false, and set error if ioctl return anything other than 0,
including any positive value.

Compare:

  if (ioctl(fd, NBD_SET_SIZE_BLOCKS, (size_t)(size / BDRV_SECTOR_SIZE) < 0))
  if (ioctl(fd, NBD_SET_SIZE_BLOCKS, (size_t)(size / BDRV_SECTOR_SIZE)) < 0)

I think the latter is the right version.

So much for trivial... ;)

Thanks,

/mjt