linux-kernel - Re: [PATCH 2/2] ocfs2: No need to zero pages past i_size. i

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Message-ID: <20100706070918.GD13023@mail.oracle.com>
Date:	Tue, 6 Jul 2010 00:09:19 -0700
From:	Joel Becker <Joel.Becker@...cle.com>
To:	Tao Ma <tao.ma@...cle.com>
Cc:	Dave Chinner <david@...morbit.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	ocfs2-devel@....oracle.com, Dave Chinner <dchinner@...hat.com>,
	Christoph Hellwig <hch@....de>, Mark Fasheh <mfasheh@...e.com>
Subject: Re: [PATCH 2/2] ocfs2: No need to zero pages past i_size. i_size v2

On Sun, Jul 04, 2010 at 11:13:01PM +0800, Tao Ma wrote:
> On 07/04/2010 05:33 AM, Joel Becker wrote:
> >@@ -1142,11 +1143,17 @@ static int ocfs2_grab_pages_for_write(struct address_space *mapping,
> >  	/*
> >  	 * Figure out how many pages we'll be manipulating here. For
> >  	 * non allocating write, we just change the one
> >-	 * page. Otherwise, we'll need a whole clusters worth.
> >+	 * page. Otherwise, we'll need a whole clusters worth.  If we're
> >+	 * writing past i_size, we only need enough pages to cover the
> >+	 * last page of the write.
> The comments for the whole function before the function name also
> needs this change accordingly?

	Not really.  That comment set a limit, this comment is more
detailed.

> >  	if (new) {
> >  		wc->w_num_pages = ocfs2_pages_per_cluster(inode->i_sb);
> >  		start = ocfs2_align_clusters_to_page_index(inode->i_sb, cpos);
> >+		/* This is the index *past* the write */
> >+		end_index = ((user_pos + user_len)>>  PAGE_CACHE_SHIFT) + 1;
> should it be
> 		end_index = ((user_pos + user_len - 1) >> PAGE_CACHE_SHIFT) + 1?

	Maybe.  Gotta think about it and test.

Joel

-- 

Life's Little Instruction Book #232

	"Keep your promises."

Joel Becker
Consulting Software Developer
Oracle
E-mail: joel.becker@...cle.com
Phone: (650) 506-8127
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