From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 405D9C34031 for ; Tue, 18 Feb 2020 05:03:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0D1DD20722 for ; Tue, 18 Feb 2020 05:03:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0D1DD20722 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=fromorbit.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 981776B0003; Tue, 18 Feb 2020 00:03:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 931946B0006; Tue, 18 Feb 2020 00:03:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8488B6B0007; Tue, 18 Feb 2020 00:03:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0027.hostedemail.com [216.40.44.27]) by kanga.kvack.org (Postfix) with ESMTP id 68A016B0003 for ; Tue, 18 Feb 2020 00:03:04 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id ED98C181AEF07 for ; Tue, 18 Feb 2020 05:03:03 +0000 (UTC) X-FDA: 76502053446.13.crow15_1aaa04abeda0a X-HE-Tag: crow15_1aaa04abeda0a X-Filterd-Recvd-Size: 6214 Received: from mail104.syd.optusnet.com.au (mail104.syd.optusnet.com.au [211.29.132.246]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Tue, 18 Feb 2020 05:03:03 +0000 (UTC) Received: from dread.disaster.area (pa49-179-138-28.pa.nsw.optusnet.com.au [49.179.138.28]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 7E1D17E99BC; Tue, 18 Feb 2020 16:03:01 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1j3v2C-0005rs-Ui; Tue, 18 Feb 2020 16:03:00 +1100 Date: Tue, 18 Feb 2020 16:03:00 +1100 From: Dave Chinner To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org Subject: Re: [PATCH v6 03/19] mm: Use readahead_control to pass arguments Message-ID: <20200218050300.GI10776@dread.disaster.area> References: <20200217184613.19668-1-willy@infradead.org> <20200217184613.19668-4-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200217184613.19668-4-willy@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=X6os11be c=1 sm=1 tr=0 a=zAxSp4fFY/GQY8/esVNjqw==:117 a=zAxSp4fFY/GQY8/esVNjqw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=l697ptgUJYAA:10 a=JfrnYn6hAAAA:8 a=7-415B0cAAAA:8 a=T1S5Ow7nDR_9LkHsJ_YA:9 a=8UYMWJo80S1V5K9C:21 a=Xcujrn6zEerIh50R:21 a=CjuIK1q_8ugA:10 a=1CNFftbPRP8L7MoqJWF3:22 a=biEYGPWJfzWAr4FL6Ov7:22 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 17, 2020 at 10:45:44AM -0800, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" > > In this patch, only between __do_page_cache_readahead() and > read_pages(), but it will be extended in upcoming patches. Also add > the readahead_count() accessor. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > include/linux/pagemap.h | 17 +++++++++++++++++ > mm/readahead.c | 36 +++++++++++++++++++++--------------- > 2 files changed, 38 insertions(+), 15 deletions(-) > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index ccb14b6a16b5..982ecda2d4a2 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -630,6 +630,23 @@ static inline int add_to_page_cache(struct page *page, > return error; > } > > +/* > + * Readahead is of a block of consecutive pages. > + */ > +struct readahead_control { > + struct file *file; > + struct address_space *mapping; > +/* private: use the readahead_* accessors instead */ > + pgoff_t _start; > + unsigned int _nr_pages; > +}; > + > +/* The number of pages in this readahead block */ > +static inline unsigned int readahead_count(struct readahead_control *rac) > +{ > + return rac->_nr_pages; > +} > + > static inline unsigned long dir_pages(struct inode *inode) > { > return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >> > diff --git a/mm/readahead.c b/mm/readahead.c > index 12d13b7792da..15329309231f 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -113,26 +113,29 @@ int read_cache_pages(struct address_space *mapping, struct list_head *pages, > > EXPORT_SYMBOL(read_cache_pages); > > -static void read_pages(struct address_space *mapping, struct file *filp, > - struct list_head *pages, unsigned int nr_pages, gfp_t gfp) > +static void read_pages(struct readahead_control *rac, struct list_head *pages, > + gfp_t gfp) > { > + const struct address_space_operations *aops = rac->mapping->a_ops; > struct blk_plug plug; > unsigned page_idx; Splitting out the aops rather than the mapping here just looks weird, especially as you need the mapping later in the function. Using aops doesn't even reduce the code side.... > > blk_start_plug(&plug); > > - if (mapping->a_ops->readpages) { > - mapping->a_ops->readpages(filp, mapping, pages, nr_pages); > + if (aops->readpages) { > + aops->readpages(rac->file, rac->mapping, pages, > + readahead_count(rac)); > /* Clean up the remaining pages */ > put_pages_list(pages); > goto out; > } > > - for (page_idx = 0; page_idx < nr_pages; page_idx++) { > + for (page_idx = 0; page_idx < readahead_count(rac); page_idx++) { > struct page *page = lru_to_page(pages); > list_del(&page->lru); > - if (!add_to_page_cache_lru(page, mapping, page->index, gfp)) > - mapping->a_ops->readpage(filp, page); > + if (!add_to_page_cache_lru(page, rac->mapping, page->index, > + gfp)) > + aops->readpage(rac->file, page); ... it just makes this less readable by splitting the if() over two lines... > put_page(page); > } > > @@ -155,9 +158,13 @@ void __do_page_cache_readahead(struct address_space *mapping, > unsigned long end_index; /* The last page we want to read */ > LIST_HEAD(page_pool); > int page_idx; > - unsigned int nr_pages = 0; > loff_t isize = i_size_read(inode); > gfp_t gfp_mask = readahead_gfp_mask(mapping); > + struct readahead_control rac = { > + .mapping = mapping, > + .file = filp, > + ._nr_pages = 0, > + }; No need to initialise _nr_pages to zero, leaving it out will do the same thing. > > if (isize == 0) > return; > @@ -180,10 +187,9 @@ void __do_page_cache_readahead(struct address_space *mapping, > * contiguous pages before continuing with the next > * batch. > */ > - if (nr_pages) > - read_pages(mapping, filp, &page_pool, nr_pages, > - gfp_mask); > - nr_pages = 0; > + if (readahead_count(&rac)) > + read_pages(&rac, &page_pool, gfp_mask); > + rac._nr_pages = 0; Hmmm. Wondering ig it make sense to move the gfp_mask to the readahead control structure - if we have to pass the gfp_mask down all the way along side the rac, then I think it makes sense to do that... Cheers, Dave. -- Dave Chinner david@fromorbit.com