From: Borislav Petkov <petkovbb@googlemail.com>
To: Tejun Heo <tj@kernel.org>
Cc: Grant Grundler <grundler@google.com>,
bzolnier@gmail.com, linux-kernel@vger.kernel.org,
axboe@kernel.dk, linux-ide@vger.kernel.org
Subject: Re: [PATCH 02/10] ide-tape: use single continuous buffer
Date: Wed, 25 Mar 2009 17:38:32 +0100 [thread overview]
Message-ID: <9ea470500903250938t35cbc403l2d0bb3ea5f1f1def@mail.gmail.com> (raw)
In-Reply-To: <49CA582B.9080706@kernel.org>
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
next prev parent reply other threads:[~2009-03-25 16:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-25 14:17 [RFC PATCHSET pata-2.6] ide: clean up ide-tape Tejun Heo
2009-03-25 14:17 ` [PATCH 01/10] ide-atapi: allow ->pc_callback() to change rq->data_len Tejun Heo
2009-03-25 14:17 ` [PATCH 02/10] ide-tape: use single continuous buffer Tejun Heo
2009-03-25 16:04 ` Grant Grundler
2009-03-25 16:13 ` Tejun Heo
2009-03-25 16:38 ` Borislav Petkov [this message]
2009-03-25 14:17 ` [PATCH 03/10] ide-tape-convert-to-bio Tejun Heo
2009-03-25 14:24 ` [PATCH 03/10 REPOST] ide-tape: use bio to carry data area Tejun Heo
2009-03-25 14:17 ` [PATCH 04/10] ide-tape: use standard data transfer mechanism Tejun Heo
2009-03-25 15:12 ` Borislav Petkov
2009-03-25 15:20 ` Borislav Petkov
2009-03-25 14:17 ` [PATCH 05/10] ide-tape: kill idetape_bh Tejun Heo
2009-03-25 14:17 ` [PATCH 06/10] ide-tape: unify r/w init paths Tejun Heo
2009-03-25 14:17 ` [PATCH 07/10] ide-tape: use byte size instead of sectors on rw issue functions Tejun Heo
2009-03-25 14:17 ` [PATCH 08/10] ide-tape: simplify read/write functions Tejun Heo
2009-03-25 14:17 ` [PATCH 09/10] ide-atapi: kill unused fields and callbacks Tejun Heo
2009-03-25 14:17 ` [PATCH 10/10] ide: drop rq->data handling from ide_map_sg() Tejun Heo
2009-03-31 7:48 ` [RFC PATCHSET pata-2.6] ide: clean up ide-tape Borislav Petkov
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