Dave Chinner
2020-Jan-29 00:24 UTC
[Ocfs2-devel] [PATCH 04/12] mm: Add readahead address space operation
On Fri, Jan 24, 2020 at 05:35:45PM -0800, Matthew Wilcox wrote:> From: "Matthew Wilcox (Oracle)" <willy at infradead.org> > > This replaces ->readpages with a saner interface: > - Return the number of pages not read instead of an ignored error code. > - Pages are already in the page cache when ->readahead is called. > - Implementation looks up the pages in the page cache instead of > having them passed in a linked list.....> diff --git a/mm/readahead.c b/mm/readahead.c > index 5a6676640f20..6d65dae6dad0 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -121,7 +121,18 @@ static void read_pages(struct address_space *mapping, struct file *filp, > > blk_start_plug(&plug); > > - if (mapping->a_ops->readpages) { > + if (mapping->a_ops->readahead) { > + unsigned left = mapping->a_ops->readahead(filp, mapping, > + start, nr_pages); > + > + while (left) { > + struct page *page = readahead_page(mapping, > + start + nr_pages - left - 1);Off by one? start = 2, nr_pages = 2, left = 1, this looks up the page at index 2, which is the one we issued IO on, not the one we "left behind" which is at index 3. Cheers, Dave. -- Dave Chinner david at fromorbit.com