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Re: [RFC] Add support for semaphore-like structure with support for asynchronous I/O

From:  Benjamin LaHaise <bcrl-AT-kvack.org>
To:  Trond Myklebust <trond.myklebust-AT-fys.uio.no>
Subject:  Re: [RFC] Add support for semaphore-like structure with support for asynchronous I/O
Date:  Tue, 5 Apr 2005 11:46:41 -0400
Cc:  Suparna Bhattacharya <suparna-AT-in.ibm.com>, Andrew Morton <akpm-AT-osdl.org>, linux-kernel-AT-vger.kernel.org, Linux Filesystem Development <linux-fsdevel-AT-vger.kernel.org>, linux-aio-AT-kvack.org
Archive-link:  Article, Thread

On Mon, Apr 04, 2005 at 01:56:35PM -0400, Trond Myklebust wrote:
> IOW: the current semaphore implementations really all need to die, and
> be replaced by a single generic version to which it is actually
> practical to add new functionality.

I can see that goal, but I don't think introducing iosems is the right 
way to acheive it.  Instead (and I'll start tackling this), how about 
factoring out the existing semaphore implementations to use a common 
lib/semaphore.c, much like lib/rwsem.c?  The iosems can be used as a 
basis for the implementation, but we can avoid having to do a giant 
s/semaphore/iosem/g over the kernel tree.

> Failing that, it is _much_ easier to convert the generic code that needs
> to support aio to use a new locking implementation and then test that.
> It is not as if conversion to aio won't involve changes to the code in
> the area surrounding those locks anyway.

Quite true.  There's a lot more work to do in this area, and these common 
primatives are needed to make progress.  Someone at netapp sent me an 
email yesterday asking about aio support in NFS, so there is some demand 
out there.  Cheers,

		-ben
-- 
"Time is what keeps everything from happening all at once." -- John Wheeler
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