From: Matthew Wilcox <willy@infradead.org> To: Miklos Szeredi <miklos@szeredi.hu> Cc: linux-xfs <linux-xfs@vger.kernel.org>, William Kucharski <william.kucharski@oracle.com>, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-mm@kvack.org, ocfs2-devel@oss.oracle.com, Dave Chinner <dchinner@redhat.com>, linux-fsdevel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Subject: Re: [PATCH v10 24/25] fuse: Convert from readpages to readahead Date: Wed, 25 Mar 2020 08:32:28 -0700 Message-ID: <20200325153228.GB22483@bombadil.infradead.org> (raw) In-Reply-To: <CAJfpegshssCJiA8PBcq2XvBj3mR8dufHb0zWRFvvKKv82VQYsw@mail.gmail.com> On Wed, Mar 25, 2020 at 03:43:02PM +0100, Miklos Szeredi wrote: > > > > - while ((page = readahead_page(rac))) { > > - if (fuse_readpages_fill(&data, page) != 0) > > + nr_pages = min(readahead_count(rac), fc->max_pages); > > Missing fc->max_read clamp. Yeah, I realised that. I ended up doing ... + unsigned int i, max_pages, nr_pages = 0; ... + max_pages = min(fc->max_pages, fc->max_read / PAGE_SIZE); > > + ia = fuse_io_alloc(NULL, nr_pages); > > + if (!ia) > > return; > > + ap = &ia->ap; > > + __readahead_batch(rac, ap->pages, nr_pages); > > nr_pages = __readahead_batch(...)? That's the other bug ... this was designed for btrfs which has a fixed-size buffer. But you want to dynamically allocate fuse_io_args(), so we need to figure out the number of pages beforehand, which is a little awkward. I've settled on this for the moment: for (;;) { struct fuse_io_args *ia; struct fuse_args_pages *ap; nr_pages = readahead_count(rac) - nr_pages; if (nr_pages > max_pages) nr_pages = max_pages; if (nr_pages == 0) break; ia = fuse_io_alloc(NULL, nr_pages); if (!ia) return; ap = &ia->ap; __readahead_batch(rac, ap->pages, nr_pages); for (i = 0; i < nr_pages; i++) { fuse_wait_on_page_writeback(inode, readahead_index(rac) + i); ap->descs[i].length = PAGE_SIZE; } ap->num_pages = nr_pages; fuse_send_readpages(ia, rac->file); } but I'm not entirely happy with that either. Pondering better options. > This will give consecutive pages, right? readpages() was already being called with consecutive pages. Several filesystems had code to cope with the pages being non-consecutive, but that wasn't how the core code worked; if there was a discontiguity it would send off the pages that were consecutive and start a new batch. __readahead_batch() can't return fewer than nr_pages, so you don't need to check for that.
next prev parent reply index Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-23 20:22 [PATCH v10 00/25] Change readahead API Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 02/25] mm: Return void from various readahead functions Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 03/25] mm: Ignore return value of ->readpages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 05/25] mm: Add new readahead_control API Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 11/25] mm: Add readahead address space operation Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox 2020-03-23 20:49 ` Eric Biggers 2020-03-24 8:40 ` Christoph Hellwig 2020-03-23 20:22 ` [PATCH v10 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox 2020-03-26 16:53 ` David Sterba 2020-03-23 20:22 ` [PATCH v10 18/25] erofs: Convert uncompressed files " Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 19/25] erofs: Convert compressed " Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 20/25] ext4: Convert " Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 24/25] fuse: Convert from readpages to readahead Matthew Wilcox 2020-03-25 9:42 ` Miklos Szeredi 2020-03-25 12:02 ` Matthew Wilcox 2020-03-25 14:43 ` Miklos Szeredi 2020-03-25 15:32 ` Matthew Wilcox [this message] 2020-03-25 15:54 ` Miklos Szeredi 2020-03-23 20:22 ` [PATCH v10 25/25] iomap: " Matthew Wilcox
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