From: Jan Kara Subject: Re: [PATCH 10/13] mm: Wire up MAP_SYNC Date: Thu, 24 Aug 2017 09:16:24 +0200 Message-ID: <20170824071624.GB20465@quack2.suse.cz> References: <20170817160815.30466-1-jack@suse.cz> <20170817160815.30466-11-jack@suse.cz> <20170823184349.GA12660@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, Andy Lutomirski , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, Ross Zwisler , Dan Williams , Boaz Harrosh To: Christoph Hellwig Return-path: Content-Disposition: inline In-Reply-To: <20170823184349.GA12660@infradead.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Wed 23-08-17 11:43:49, Christoph Hellwig wrote: > On Thu, Aug 17, 2017 at 06:08:12PM +0200, Jan Kara wrote: > > Pretty crude for now... > > > > Signed-off-by: Jan Kara > > --- > > fs/ext4/file.c | 2 ++ > > include/linux/mm.h | 1 + > > include/linux/mman.h | 3 ++- > > include/uapi/asm-generic/mman.h | 1 + > > mm/mmap.c | 5 +++++ > > 5 files changed, 11 insertions(+), 1 deletion(-) > > > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c > > index f84bb29e941e..850037e140d7 100644 > > --- a/fs/ext4/file.c > > +++ b/fs/ext4/file.c > > @@ -340,6 +340,8 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma) > > vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE; > > } else { > > vma->vm_ops = &ext4_file_vm_ops; > > + if (vma->vm_flags & VM_SYNC) > > + return -EOPNOTSUPP; > > } > > So each mmap instance would need to reject the flag explicitly? > > Or do I misunderstand this VM_SYNC flag? Yes, if this should be cleaned up, then each mmap instance not supporting it would need to reject it. However Dan has in his version of mmap() syscall a mask of supported flags so when I switch to that, it would be just opt-in. Or I could just reject VM_SYNC for any !IS_DAX inode so then only ext2 & xfs would need to reject it... But the biggest problem with this patch is that we need to settle on a safe way of adding new mmap flag. Honza -- Jan Kara SUSE Labs, CR