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SubjectRe: [Ext2-devel] [PATCH 2/2] ext2/3: Support2^32-1blocks(e2fsprogs)
Mingming Cao <cmm@us.ibm.com> wrote:
>
> I am wondering if we have (or plan to have) "long long " type of percpu
> counters? Andrew, Kiran, do you know?
>
> It seems right now the percpu counters are used mostly by ext2/3 for
> filesystem free blocks accounting. Right now the counter is "long" type,
> which is not enough if we want to extend the filesystem limit from 2**31
> to 2**32 on 32 bit machine.
>
> The patch from Takashi copies the whole percpu_count.h and create a new
> percpu_llcounter.h to support longlong type percpu counters. I am
> wondering is there any better way for this?
>

I can't immediately think of anything smarter.

One could of course implement a 64-bit percpu counter by simply
concatenating two 32-bit counters. That would be a little less efficient,
but would introduce less source code and would mean that we don't need to
keep two different implemetations in sync. But one would need to do a bit
of implementation, see how bad it looks.
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