On Thu, Feb 20, 2020 at 06:54:00PM +0100, David Sterba wrote: > On Wed, Feb 19, 2020 at 01:00:39PM -0800, Matthew Wilcox wrote: > > From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> > > > > This series adds a readahead address_space operation to eventually > > replace the readpages operation. The key difference is that > > pages are added to the page cache as they are allocated (and > > then looked up by the filesystem) instead of passing them on a > > list to the readpages operation and having the filesystem add > > them to the page cache. It's a net reduction in code for each > > implementation, more efficient than walking a list, and solves > > the direct-write vs buffered-read problem reported by yu kuai at > > https://lore.kernel.org/linux-fsdevel/20200116063601.39201-1-yukuai3@xxxxxxxxxx/ > > > > The only unconverted filesystems are those which use fscache. > > Their conversion is pending Dave Howells' rewrite which will make the > > conversion substantially easier. > > > > I want to thank the reviewers; Dave Chinner, John Hubbard and Christoph > > Hellwig have done a marvellous job of providing constructive criticism. > > Eric Biggers pointed out how I'd broken ext4 (which led to a substantial > > change). I've tried to take it all on board, but I may have missed > > something simply because you've done such a thorough job. > > > > This series can also be found at > > http://git.infradead.org/users/willy/linux-dax.git/shortlog/refs/tags/readahead_v7 > > (I also pushed the readahead_v6 tag there in case anyone wants to diff, and > > they're both based on 5.6-rc2 so they're easy to diff) > > > > v7: > > - Now passes an xfstests run on ext4! > > On btrfs it still chokes on the first test btrfs/001, with the following > warning, the test is stuck there. Thanks. The warning actually wasn't the problem, but it did need to be addressed. I got a test system up & running with btrfs, and it's currently on generic/027 with the following patch: diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 9c782c15f7f7..d23a224d2ad2 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -676,7 +676,7 @@ static inline unsigned int __readahead_batch(struct readahead_control *rac, struct page **array, unsigned int array_sz) { unsigned int i = 0; - XA_STATE(xas, &rac->mapping->i_pages, rac->_index); + XA_STATE(xas, &rac->mapping->i_pages, 0); struct page *page; BUG_ON(rac->_batch_count > rac->_nr_pages); @@ -684,6 +684,8 @@ static inline unsigned int __readahead_batch(struct readahead_control *rac, rac->_index += rac->_batch_count; rac->_batch_count = 0; + xas_set(&xas, rac->_index); + rcu_read_lock(); xas_for_each(&xas, page, rac->_index + rac->_nr_pages - 1) { VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(PageTail(page), page); @@ -702,6 +704,7 @@ static inline unsigned int __readahead_batch(struct readahead_control *rac, if (i == array_sz) break; } + rcu_read_unlock(); return i; }
