linux-kernel - Re: [PATCH] hugetlbfs read() support

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Message-Id: <1184966133.21127.0.camel@dyn9047017100.beaverton.ibm.com>
Date:	Fri, 20 Jul 2007 14:15:33 -0700
From:	Badari Pulavarty <pbadari@...ibm.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Bill Irwin <bill.irwin@...cle.com>, nacc@...ibm.com,
	lkml <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] hugetlbfs read() support

On Fri, 2007-07-20 at 14:29 +1000, Nick Piggin wrote:
> Andrew Morton wrote:
> > On Thu, 19 Jul 2007 08:51:49 -0700 Badari Pulavarty <pbadari@...ibm.com> wrote:
> > 
> > 
> >>>>+		}
> >>>>+
> >>>>+		offset += ret;
> >>>>+		retval += ret;
> >>>>+		len -= ret;
> >>>>+		index += offset >> HPAGE_SHIFT;
> >>>>+		offset &= ~HPAGE_MASK;
> >>>>+
> >>>>+		page_cache_release(page);
> >>>>+		if (ret == nr && len)
> >>>>+			continue;
> >>>>+		goto out;
> >>>>+	}
> >>>>+out:
> >>>>+	return retval;
> >>>>+}
> >>>
> >>>This code doesn't have all the ghastly tricks which we deploy to handle
> >>>concurrent truncate.
> >>
> >>Do I need to ? Baaahh!!  I don't want to deal with them. 
> > 
> > 
> > Nick, can you think of any serious consequences of a read/truncate race in
> > there?  I can't..
> 
> As it doesn't allow writes, then I _think_ it should be OK. If you
> ever did want to add write(2) support, then you would have transient
> zeroes problems.

I have no plans to add write() support - unless there is real reason
for doing so.

> 
> But why not just hold i_mutex around the whole thing just to be safe?

Yeah. I can do that, just to be safe for future..

Thanks,
Badari

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