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Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges
From: |
Olaf Hering |
Subject: |
Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges |
Date: |
Fri, 18 Nov 2016 18:41:09 +0100 |
User-agent: |
Mutt/1.6.2 (6759) |
On Fri, Nov 18, Eric Blake wrote:
> On 11/18/2016 04:24 AM, Olaf Hering wrote:
> > + /* Overflowing byte limit? */
> > + if ((sec_start + sec_count) > ((INT64_MAX + INT_MAX) >>
> > BDRV_SECTOR_BITS)) {
> This is undefined. INT64_MAX + anything non-negative overflows int64,
The expanded value used to be stored into a uint64_t before it was used
here. A "cleanup" introduced this error. Thanks for spotting.
> If you are trying to detect guests that make a request that would cover
> more than INT64_MAX bytes, you can simplify. Besides, for as much
> storage as there is out there, I seriously doubt ANYONE will ever have
> 2^63 bytes addressable through a single device. Why not just write it as:
>
> if ((INT64_MAX >> BDRV_SECTOR_BITS) - sec_count < sec_start) {
That would always be false I think. I will resubmit with this:
if ((sec_start + sec_count) > (INT64_MAX >> BDRV_SECTOR_BITS)) {
Regarding the cast for ->req, it has type blkif_request_t, but the
pointer needs to be assigned to type blkif_request_discard_t.
Olaf
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- [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges, Olaf Hering, 2016/11/18
- Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges, Eric Blake, 2016/11/18
- Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges,
Olaf Hering <=
- Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges, Eric Blake, 2016/11/18
- Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges, Olaf Hering, 2016/11/22
- Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges, Eric Blake, 2016/11/22
- Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges, Olaf Hering, 2016/11/22
- Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges, Eric Blake, 2016/11/22