linux-kernel - Re: [PATCH v6 06/22] Replace XIP read and write with DAX I/O

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Message-ID: <20140311125357.GA7580@linux.intel.com>
Date:	Tue, 11 Mar 2014 08:53:57 -0400
From:	Matthew Wilcox <willy@...ux.intel.com>
To:	Toshi Kani <toshi.kani@...com>
Cc:	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v6 06/22] Replace XIP read and write with DAX I/O

On Mon, Mar 10, 2014 at 06:32:38PM -0600, Toshi Kani wrote:
> On Tue, 2014-02-25 at 09:18 -0500, Matthew Wilcox wrote:
> > Use the generic AIO infrastructure instead of custom read and write
> > methods.  In addition to giving us support for AIO, this adds the missing
> > locking between read() and truncate().
> > 
>  :
> > +static void dax_new_buf(void *addr, unsigned size, unsigned first,
> > +					loff_t offset, loff_t end, int rw)
> > +{
> > +	loff_t final = end - offset;	/* The final byte in this buffer */
> 
> I may be missing something, but shouldn't it take first into account?
> 
> 	loff_t final = end - offset + first;

Yes it should.  Thanks!  (Fortunately, this is only a performance problem
as we'll end up zeroing more than we ought to, which is fine as it will
be overwritten by the copy_from_user later)

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