From: Jens Axboe <axboe@suse.de>
To: Pekka J Enberg <penberg@cs.Helsinki.FI>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC/PATCH] block: undeprecate ll_rw_block()
Date: Tue, 7 Feb 2006 08:41:36 +0100 [thread overview]
Message-ID: <20060207074136.GA4210@suse.de> (raw)
In-Reply-To: <Pine.LNX.4.58.0602070909370.25555@sbz-30.cs.Helsinki.FI>
On Tue, Feb 07 2006, Pekka J Enberg wrote:
> On Mon, Feb 06 2006, Pekka Enberg wrote:
> > > This patch removes the DEPRECATED comment from ll_rw_block(). The function
> > > is still in active use and there isn't any real replacement for it.
>
> On Mon, 6 Feb 2006, Jens Axboe wrote:
> > It is still deprecated, so I think the comment should stay. There are
> > plenty ways to accomplish what ll_rw_block does (and more efficiently,
> > array of bh's is not very nice to say the least) and the buffer_head
> > isn't even an io unit anymore.
>
> To clarify, what ways are there? When we need to access the data, use
> submit_bh() and when we just want the I/O to be done,
> generic_make_request()?
Generally you want to move to using a bio instead of a bh. Once you do
that, you can submit > 1 page of io a lot more efficiently than what
ll_rw_block() is doing. submit_bh() is just a 'wrapper' on top of the
real io interface, your explanation of the two doesn't make sense.
generic_make_request() is typically something a low level driver like md
or dm would use to submit a formed bio to a device, it's not something
you'd expect other parts of the kernel to use. If you look at the newer
io parts in the kernel (in fs/ and mm/), you'll see them using
submit_bio() mostly.
--
Jens Axboe
prev parent reply other threads:[~2006-02-07 7:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-06 19:36 [RFC/PATCH] block: undeprecate ll_rw_block() Pekka Enberg
2006-02-06 21:07 ` Jens Axboe
2006-02-07 7:20 ` Pekka J Enberg
2006-02-07 7:41 ` Jens Axboe [this message]
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