Re: [PATCH 2/4] fs: btrfs: volumes: prevent overflow for multiplying

Re: [PATCH 2/4] fs: btrfs: volumes: prevent overflow for multiplying

[Qu Wenruo]

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On 2020/11/2 上午8:20, Qu Wenruo wrote:
> 
> 
> On 2020/11/2 上午7:02, Marek Behun wrote:
>> On Sat, 31 Oct 2020 09:07:50 +0800
>> Qu Wenruo <wqu@suse.com> wrote:
>>
>>> In real world, this should not cause problem as we have device number
>>> limit thus it won't go beyond 4G for a single stripe.
>>
>> So we can't run into this overflow in U-Boot because only one device is
>> supported? But in Linux we can run into this issue?
>>
> In kernel, we have device number check, IIRC for default nodesize is
> just several donzens of devices.
> And since each stripe is only 64K fixed in btrfs, you can see it won't
> go beyond 4G even in kernel.

Sorry, the 64K stripe_len is only for RAID56, and for kernel, we always
use u64 for stripe_len, thus we won't hit the problem.

The problem is in btrfs-progs, where the code comes from, we use int,
other than u64.

Thanks for the hint for the root cause, would related values to be u64
for both btrfs-progs and u-boot to follow the kernel scheme.

Thanks,
Qu
> 
> Thanks,
> Qu
> 


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