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From: "Sébastien Dugué" <sebastien.dugue@bull.net>
To: Zach Brown <zach.brown@oracle.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
	linux-aio <linux-aio@kvack.org>, Andrew Morton <akpm@osdl.org>,
	Suparna Bhattacharya <suparna@in.ibm.com>,
	Christoph Hellwig <hch@infradead.org>,
	Badari Pulavarty <pbadari@us.ibm.com>,
	Ulrich Drepper <drepper@redhat.com>,
	Jean Pierre Dion <jean-pierre.dion@bull.net>
Subject: Re: [PATCH -mm 1/5][AIO] - Rework compat_sys_io_submit
Date: Thu, 30 Nov 2006 10:57:10 +0100	[thread overview]
Message-ID: <20061130105710.572d3c6e@frecb000686> (raw)
In-Reply-To: <8BA392C6-FCCB-40BD-9CCF-3EF56C3491BD@oracle.com>

On Wed, 29 Nov 2006 16:47:47 -0800, Zach Brown <zach.brown@oracle.com> wrote:

> On Nov 29, 2006, at 2:32 AM, Sébastien Dugué wrote:
> 
> >                  compat_sys_io_submit() cleanup
> >
> >
> >   Cleanup compat_sys_io_submit by duplicating some of the native  
> > syscall
> > logic in the compat layer and directly calling io_submit_one() instead
> > of fooling the syscall into thinking it is called from a native 64-bit
> > caller.
> >
> >   This is needed for the completion notification patch to avoid having
> > to rewrite each iocb on the caller stack for sys_io_submit() to  
> > find the
> > sigevents.
> 
> You could explicitly mention that this eliminates:
> 
>   - the overhead of copying nr pointers on the userspace caller's stack
> 
>   - the arbitrary PAGE_SIZE/(sizeof(void *)) limit on the number of  
> iocbs that can be submitted
> 
> Those alone make this worth merging.

  Right, will add.

> 
> > +	if (unlikely(!access_ok(VERIFY_READ, iocb, (nr * sizeof(u32)))))
> > +		return -EFAULT;
> 
> I'm glad you got that right :)  I no doubt would have initially  
> hoisted these little checks into a shared helper function and missed  
> that detail of getting the size of the access_ok() right in the  
> compat case.

  Thanks.

> 
> > +	put_ioctx(ctx);
> > +
> > +	return i? i: ret;
> 
> sys_io_getevents() reads:

 uh!     ^^^^^^^^^    you must be meaning sys_io_submit()?

> 
>          put_ioctx(ctx);
>          return i ? i : ret;
> 
> So while this compat_sys_io_submit() logic seems fine and I would be  
> comfortable with it landing as-is, I'd also appreciate it if we  
> didn't introduce differences between the two functions when it seems  
> just as easy to make them the same.  (That chunk is just one  
> example.  There's whitespace, missing unlikely()s, etc).
> 

  OK, will fix.

  Thanks,

  Sébastien.


  

  reply	other threads:[~2006-11-30  9:58 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-11-29 10:24 [PATCH -mm 0/5][AIO] - AIO completion signal notification v3 Sébastien Dugué
2006-11-29 10:32 ` [PATCH -mm 1/5][AIO] - Rework compat_sys_io_submit Sébastien Dugué
2006-11-30  0:47   ` Zach Brown
2006-11-30  9:57     ` Sébastien Dugué [this message]
2006-11-30 17:27       ` Zach Brown
2006-11-29 10:32 ` [PATCH -mm 2/5][AIO] - fix aio.h includes Sébastien Dugué
2006-11-29 10:32 ` [PATCH -mm 3/5][AIO] - export good_sigevent() Sébastien Dugué
2006-11-29 10:38   ` Christoph Hellwig
2006-11-29 10:46     ` Sébastien Dugué
2006-11-29 14:54   ` Christoph Hellwig
2006-11-29 16:10     ` Sébastien Dugué
2006-12-04 17:13   ` Bharata B Rao
2006-12-05  8:30     ` Sébastien Dugué
2006-11-29 10:33 ` [PATCH -mm 4/5][AIO] - AIO completion signal notification Sébastien Dugué
2006-11-29 10:51   ` Christoph Hellwig
2006-11-29 13:08     ` Sébastien Dugué
2006-11-29 13:50       ` Christoph Hellwig
2006-11-29 14:18         ` Sébastien Dugué
2006-11-29 11:33   ` Jakub Jelinek
2006-11-29 13:25     ` Sébastien Dugué
2006-11-29 10:33 ` [PATCH -mm 5/5][AIO] - Listio support Sébastien Dugué
2006-11-30  8:25   ` Suparna Bhattacharya
2006-11-30 10:04     ` Sébastien Dugué
2006-11-30 15:38 [PATCH -mm 0/5][AIO] - AIO completion signal notification v4 Sébastien Dugué
2006-11-30 15:49 ` [PATCH -mm 1/5][AIO] - Rework compat_sys_io_submit Sébastien Dugué
     [not found] <20070117104601.36b2ab18@frecb000686>
2007-01-17  9:48 ` Sébastien Dugué

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