From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:52422 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729258AbfDJIZI (ORCPT ); Wed, 10 Apr 2019 04:25:08 -0400 Date: Wed, 10 Apr 2019 10:25:04 +0200 From: Jan Kara Subject: Re: [PATCH v5 4/6] dax: check synchronous mapping is supported Message-ID: <20190410082504.GF1426@quack2.suse.cz> References: <20190410040826.24371-1-pagupta@redhat.com> <20190410040826.24371-5-pagupta@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190410040826.24371-5-pagupta@redhat.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Pankaj Gupta Cc: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-acpi@vger.kernel.org, qemu-devel@nongnu.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, dan.j.williams@intel.com, zwisler@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, mst@redhat.com, jasowang@redhat.com, willy@infradead.org, rjw@rjwysocki.net, hch@infradead.org, lenb@kernel.org, jack@suse.cz, tytso@mit.edu, adilger.kernel@dilger.ca, darrick.wong@oracle.com, lcapitulino@redhat.com, kwolf@redhat.com, imammedo@redhat.com, jmoyer@redhat.com, nilal@redhat.com, riel@surriel.com, stefanha@redhat.com, aarcange@redhat.com, david@redhat.com, david@fromorbit.com, cohuck@redhat.com, xiaoguangrong.eric@gmail.com, pbonzini@redhat.com, kilobyte@angband.pl, yuval.shaia@oracle.com On Wed 10-04-19 09:38:24, Pankaj Gupta wrote: > This patch introduces 'daxdev_mapping_supported' helper > which checks if 'MAP_SYNC' is supported with filesystem > mapping. It also checks if corresponding dax_device is > synchronous. Virtio pmem device is asynchronous and > does not not support VM_SYNC. > > Suggested-by: Jan Kara > Signed-off-by: Pankaj Gupta > --- > include/linux/dax.h | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/include/linux/dax.h b/include/linux/dax.h > index b896706a5ee9..4a2a60ffec86 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -38,6 +38,24 @@ void kill_dax(struct dax_device *dax_dev); > void dax_write_cache(struct dax_device *dax_dev, bool wc); > bool dax_write_cache_enabled(struct dax_device *dax_dev); > bool dax_synchronous(struct dax_device *dax_dev); > + > +/* > + * Callers check if synchronous mapping is enabled for DAX file > + * and attached dax device is also synchronous. > + * > + * dax_synchronous function verifies if dax device is synchronous. > + * Currently, only virtio pmem device supports asynchronous device > + * flush. > + */ Thanks for the patch! I'd restructure this comment like: /* * Check if given mapping is supported by the file / underlying device. */ > +static inline bool daxdev_mapping_supported(struct vm_area_struct *vma, > + struct dax_device *dax_dev) > +{ /* Everyone supports non-sync mappings */ > + if (!(vma->vm_flags & VM_SYNC)) > + return true; /* Sync mappings are supported only for files using DAX */ > + if (!IS_DAX(file_inode(vma->vm_file))) > + return false; /* Underlying device must support persisting through CPU instructions */ > + return dax_synchronous(dax_dev); > +} > #else > static inline struct dax_device *dax_get_by_host(const char *host) > { > @@ -69,6 +87,11 @@ static inline bool dax_synchronous(struct dax_device *dax_dev) > { > return true; > } > +static inline bool daxdev_mapping_supported(struct vm_area_struct *vma, > + struct dax_device *dax_dev) > +{ > + return true; This looks wrong. Shouldn't it rather be: return !(vma->flags & VM_SYNC); ? Honza -- Jan Kara SUSE Labs, CR