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From: Joel Becker on 6 Jul 2010 03:20
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(a)oracle.com
Phone: (650) 506-8127
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From: Joel Becker on 6 Jul 2010 03:20
On Mon, Jul 05, 2010 at 09:38:42AM +0800, Tao Ma wrote:
> btw, do we ever have a chance that start + wc->w_num_pages >
> end_index? I can't find it.

Of course. If you have a 1MB clustersize, w_num_pages will be
256. But if you are only writing the first page of the cluster,
end_index is only 1.

Joel

--

"If you took all of the grains of sand in the world, and lined
them up end to end in a row, you'd be working for the government!"
- Mr. Interesting

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