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SubjectRe: [PATCH 02/10] ide-tape: use single continuous buffer
From
Hi,

On Wed, Mar 25, 2009 at 5:13 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello, Grant.
>
> Grant Grundler wrote:
>> On Wed, Mar 25, 2009 at 7:17 AM, Tejun Heo <tj@kernel.org> wrote:
>>> Impact: simpler buffer allocation and handling, fix DMA transfers
>> ...
>>> +               atomic_set(&bh->b_count, bcount);
>>>                if (atomic_read(&bh->b_count) == bh->b_size)
>> ...
>>
>> I'm failing to see why bh->b_count is an atomic_t.
>> I always assumed tapes were exclusive access devices
>> and would be serialized at a higher level.
>
> Beats me.  I don't know.  The code is generally pretty over-engineered
> but, well, it's an ancient piece of code with (probably too) rich
> history.

Yep, actually the driver was even bigger and it implemented a bunch of fun stuff
like command pipelining and those atomics had to protect the pipeline from
simultaneous ->open()s through its chrdev interface, IIRC.

--
Regards/Gruss,
Boris
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