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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 9CE4DC43331 for ; Thu, 4 Mar 2021 00:20:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E69064E6C for ; Thu, 4 Mar 2021 00:20:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383092AbhCDATO (ORCPT ); Wed, 3 Mar 2021 19:19:14 -0500 Received: from verein.lst.de ([213.95.11.211]:36165 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356550AbhCCKrm (ORCPT ); Wed, 3 Mar 2021 05:47:42 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id 9A87668BEB; Wed, 3 Mar 2021 10:28:08 +0100 (CET) Date: Wed, 3 Mar 2021 10:28:08 +0100 From: Christoph Hellwig To: Shiyang Ruan Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, darrick.wong@oracle.com, dan.j.williams@intel.com, willy@infradead.org, jack@suse.cz, viro@zeniv.linux.org.uk, linux-btrfs@vger.kernel.org, ocfs2-devel@oss.oracle.com, david@fromorbit.com, hch@lst.de, rgoldwyn@suse.de Subject: Re: [PATCH v2 02/10] fsdax: Factor helper: dax_fault_actor() Message-ID: <20210303092808.GC12784@lst.de> References: <20210226002030.653855-1-ruansy.fnst@fujitsu.com> <20210226002030.653855-3-ruansy.fnst@fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210226002030.653855-3-ruansy.fnst@fujitsu.com> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Feb 26, 2021 at 08:20:22AM +0800, Shiyang Ruan wrote: > The core logic in the two dax page fault functions is similar. So, move > the logic into a common helper function. Also, to facilitate the > addition of new features, such as CoW, switch-case is no longer used to > handle different iomap types. > > Signed-off-by: Shiyang Ruan > --- > fs/dax.c | 211 ++++++++++++++++++++++++++++++------------------------- > 1 file changed, 117 insertions(+), 94 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index 7031e4302b13..9dea1572868e 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -1289,6 +1289,93 @@ static int dax_fault_cow_page(struct vm_fault *vmf, struct iomap *iomap, > return 0; > } > > +static vm_fault_t dax_fault_insert_pfn(struct vm_fault *vmf, pfn_t pfn, > + bool pmd, bool write) > +{ > + vm_fault_t ret; > + > + if (!pmd) { > + struct vm_area_struct *vma = vmf->vma; > + unsigned long address = vmf->address; > + > + if (write) > + ret = vmf_insert_mixed_mkwrite(vma, address, pfn); > + else > + ret = vmf_insert_mixed(vma, address, pfn); > + } else > + ret = vmf_insert_pfn_pmd(vmf, pfn, write); What about simplifying this a little bit more, something like: if (pmd) return vmf_insert_pfn_pmd(vmf, pfn, write); if (write) return vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn); return vmf_insert_mixed(vmf->vma, vmf->address, pfn); also given that this only has a single user, why not keep open coding it in the caller? > +#ifdef CONFIG_FS_DAX_PMD > +static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, > + struct iomap *iomap, void **entry); > +#else > +static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf, > + struct iomap *iomap, void **entry) > +{ > + return VM_FAULT_FALLBACK; > +} > +#endif Can we try to avoid the forward declaration? Also is there a reason dax_pmd_load_hole does not compile for the !CONFIG_FS_DAX_PMD case? If it compiles fine we can just rely on IS_ENABLED() based dead code elimination entirely. > + /* if we are reading UNWRITTEN and HOLE, return a hole. */ > + if (!write && > + (iomap->type == IOMAP_UNWRITTEN || iomap->type == IOMAP_HOLE)) { > + if (!pmd) > + return dax_load_hole(xas, mapping, &entry, vmf); > + else > + return dax_pmd_load_hole(xas, vmf, iomap, &entry); > + } > + > + if (iomap->type != IOMAP_MAPPED) { > + WARN_ON_ONCE(1); > + return VM_FAULT_SIGBUS; > + } Nit: I'd use a switch statement here for a clarity: switch (iomap->type) { case IOMAP_MAPPED: break; case IOMAP_UNWRITTEN: case IOMAP_HOLE: if (!write) { if (!pmd) return dax_load_hole(xas, mapping, &entry, vmf); return dax_pmd_load_hole(xas, vmf, iomap, &entry); } break; default: WARN_ON_ONCE(1); return VM_FAULT_SIGBUS; } > + err = dax_iomap_pfn(iomap, pos, size, &pfn); > + if (err) > + goto error_fault; > + > + entry = dax_insert_entry(xas, mapping, vmf, entry, pfn, 0, > + write && !sync); > + > + if (sync) > + return dax_fault_synchronous_pfnp(pfnp, pfn); > + > + ret = dax_fault_insert_pfn(vmf, pfn, pmd, write); > + > +error_fault: > + if (err) > + ret = dax_fault_return(err); > + > + return ret; It seems like the only place that sets err is the dax_iomap_pfn case above. So I'd move the dax_fault_return there, which then allows a direct return for everyone else, including the open coded version of dax_fault_insert_pfn. I really like where this is going!