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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_NEOMUTT 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 12947C282CE for ; Wed, 22 May 2019 19:11:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E247A20868 for ; Wed, 22 May 2019 19:11:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729506AbfEVTLo (ORCPT ); Wed, 22 May 2019 15:11:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:35800 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728734AbfEVTLn (ORCPT ); Wed, 22 May 2019 15:11:43 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 8DEEBAC6E; Wed, 22 May 2019 19:11:42 +0000 (UTC) Date: Wed, 22 May 2019 14:11:39 -0500 From: Goldwyn Rodrigues To: "Darrick J. Wong" Cc: linux-btrfs@vger.kernel.org, kilobyte@angband.pl, linux-fsdevel@vger.kernel.org, jack@suse.cz, david@fromorbit.com, willy@infradead.org, hch@lst.de, dsterba@suse.cz, nborisov@suse.com, linux-nvdimm@lists.01.org Subject: Re: [PATCH 08/18] dax: memcpy page in case of IOMAP_DAX_COW for mmap faults Message-ID: <20190522191139.62v2rgby5ptjhzcd@fiona> References: <20190429172649.8288-1-rgoldwyn@suse.de> <20190429172649.8288-9-rgoldwyn@suse.de> <20190521174625.GF5125@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521174625.GF5125@magnolia> User-Agent: NeoMutt/20180716 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 10:46 21/05, Darrick J. Wong wrote: > On Mon, Apr 29, 2019 at 12:26:39PM -0500, Goldwyn Rodrigues wrote: > > From: Goldwyn Rodrigues > > > > Change dax_iomap_pfn to return the address as well in order to > > use it for performing a memcpy in case the type is IOMAP_DAX_COW. > > We don't handle PMD because btrfs does not support hugepages. > > > > Question: > > The sequence of bdev_dax_pgoff() and dax_direct_access() is > > used multiple times to calculate address and pfn's. Would it make > > sense to call it while calculating address as well to reduce code? > > > > Signed-off-by: Goldwyn Rodrigues > > --- > > fs/dax.c | 19 +++++++++++++++---- > > 1 file changed, 15 insertions(+), 4 deletions(-) > > > > diff --git a/fs/dax.c b/fs/dax.c > > index 610bfa861a28..718b1632a39d 100644 > > --- a/fs/dax.c > > +++ b/fs/dax.c > > @@ -984,7 +984,7 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos) > > } > > > > static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size, > > - pfn_t *pfnp) > > + pfn_t *pfnp, void **addr) > > { > > const sector_t sector = dax_iomap_sector(iomap, pos); > > pgoff_t pgoff; > > @@ -996,7 +996,7 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size, > > return rc; > > id = dax_read_lock(); > > length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size), > > - NULL, pfnp); > > + addr, pfnp); > > if (length < 0) { > > rc = length; > > goto out; > > @@ -1286,6 +1286,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, > > XA_STATE(xas, &mapping->i_pages, vmf->pgoff); > > struct inode *inode = mapping->host; > > unsigned long vaddr = vmf->address; > > + void *addr; > > loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT; > > struct iomap iomap = { 0 }; > > Ugh, I had forgotten that fs/dax.c open-codes iomap_apply, probably > because the actor returns vm_fault_t, not bytes copied. I guess that > makes it a tiny bit more complicated to pass in two (struct iomap *) to > the iomap_begin function... I am not sure I understand this. We do not use iomap_apply() in the fault path: dax_iomap_pte_fault(). We just use iomap_begin() and iomap_end(). So, why can we not implement your idea of using two iomaps? What does open-coding iomap-apply mean? -- Goldwyn